A system and method for ionizing molecular oxygen

Abstract

Embodiments pertain to a laser arrangement configured for enhancement of an ionizaon process of molecular oxygen by causing a two-photon-based transion followed by a (e.g., disnct) third photon- based transion for ionizing the molecular oxygen. In some examples, the laser arrangement comprises at least one laser source configured to output towards at least one oxygen molecule laser light having mulple wavelengths (WL), as follows: outpu[ng at least one electromagnec (EM) radiaon within a first WL range adapted to cause two-photon-based excitaon of the molecular oxygen into a (e.g., disnct) excited state; and outpu[ng at least one addional EM radiaon that is within a second WL range adapted to cause ionizaon of the molecular oxygen from the (e.g., disnct) excited state.

Description

[0001] A SYSTEM AND METHOD FOR IONIZING MOLECULAR OXYGEN CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This applica^on claims priority and / or benefit of US Provisional Patent Applica^on No.63 / 553,663filed on February 15, 2024, ^tled “Efficient Laser Igni^on by Two-color Resonant Mul^photon Ioniza^on of Oxygen”; and from US Provisional Patent Applica^on No. 63 / 726,270,filed November 28, 2024, ^tled “Resonance Enhanced Mul^photon Ioniza^on Detec^on of Vibra^onally Excited O2”. The contents of the above applica^ons are all incorporated by reference as if fully set forth herein. BACKGROUND

[0002] Ioniza^on refers to the process where an atom or molecule gains enough energy to eject one or more electrons, resul^ng in the forma^on of an ion. In the context of photoioniza^on, this process is typically ini^ated by the absorp^on of photons from electromagne^c radia^on. The energy of the absorbed photons must exceed the ioniza^on energy of the atom or molecule to remove an electron.

[0003] REMPI (resonance-enhanced mul^photon ioniza^on) is an outstanding technique in which ioniza^on is achieved by the simultaneous absorp^on of mul^ple photons of high intensity, with resonance playing a crucial role in the process. This method is typically used for detec^ng and studying atoms, molecules, clusters, and desorbed molecules in the gas phase, or vola^lized liquids and solids providing a powerful tool for spectroscopic analysis. REMPI is widely used in areas like mass spectrometry, chemical reac^on dynamics, determining molecular proper^es, and atmospheric analysis.

[0004] The descrip^on above is presented as a general overview of related art in thisfield and should not be construed as an admission that any of the informa^on it contains cons^tutes prior art against the present patent applica^on. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] In the following descrip^on, for purposes of explana^on and not limita^on, details and descrip^ons are set forth to provide a thorough understanding of the present disclosure.

[0006] However, it will be apparent to those skilled in the art that the present disclosure may be prac^ced in other embodiments that depart from these details and descrip^ons.

[0007] In the following descrip^on, thefigures which are described illustrate generally, by way of example, but not by way of limita^on, various embodiments discussed in the present document.

[0008] For simplicity and clarity of illustra^on, elements shown in thefigures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated rela^ve to other elements for clarity of presenta^on.

[0009] Furthermore, reference numerals may be repeated among thefigures to indicate corresponding and / or analogous elements. References to previously presented elements are implied without necessarily further ci^ng the drawing and / or descrip^on in which they appear.

[0010] The expression “perspec^ve view” may also encompass the meaning of the term “isometric view” and / or any other representa^on of three-dimensional (3D) objects in a two-dimensional (2D format).

[0011] The number of elements shown in the Figures should by no means be construed as limi^ng and is for illustra^ve purposes only. Thefigures are listed below.

[0012] Figure 1 is a schema^c illustra^on of an ioniza^on system of molecular oxygen configured to facilitate two-color (2+1’) REMPI, according to some embodiments.

[0013] Figure 2 is a schema^c illustra^on of a detec^on system of molecular oxygen configured to ionize the molecular oxygen to facilitate the detec^on, according to some embodiments.

[0014] Figure 3 is a schema^cflowchart diagram of a detec^on method of molecular oxygen facilitated by two-color (2+1’) REMPI, according to some embodiments.

[0015] Figure 4 is an elabora^ve schema^c illustra^on of a detec^on system of molecular oxygen configured to ionize the molecular oxygen to facilitate the detec^on, according to some embodiments.

[0016] Figure 5 is an addi^onal schema^c illustra^on of molecular oxygen detec^on scheme, according to some embodiments.

[0017] Figure 6 schema^cally depicts a one-color resonance-enhanced two-photon ioniza^on (R2PI) process, according to some embodiments.

[0018] Figure 7 schema^cally depicts a one-color (2 + 1) REMPI process, according to some embodiments.

[0019] Figure 8 schema^cally depicts a two-color (2 + 1’) REMPI process according to some embodiments.

[0020] Figure 9 is a schema^cflowchart diagram of a detec^on method of molecular oxygen facilitated by three-color [(1 + 1’) + 1’’] REMPI, according to some embodiments.

[0021] Figure 10 schema^cally depicts a three-color [(1 + 1’) + 1’’] REMPI process, according to some embodiments.

[0022] Addi^onally, the present disclosure presentsfigures associated with scien^fic experiments and simula^ons of molecular ioniza^on method and system.

[0023] Figure A1 schema^cally depicts resonance-enhanced mul^photon ioniza^on (REMPI) schemes used for molecular oxygen detec^on, according to some embodiments.

[0024] Figure A2 schema^cally depicts a spectrum recorded via REMPI schemes of O2, according to some embodiments.

[0025] Figure A3 schema^cally depicts a par^al resonance-enhanced mul^photon ioniza^on (REMPI) spectra of the 3dπ Rydberg state (vʹ = 0 or 1), according to some embodiments.

[0026] Figure B1 schema^cally depicts measured REMPI spectra of the 3dπ (vʹ = 0) ←X^Σ^^(vʹʹ = 0, 1) Rydberg two-photon transi^ons of molecular oxygen at various rota^onal according to some embodiments

[0027] Figure B2 schema^cally depicts a REMPI spectra of the 3dπ (vʹ =0) ←X^Σ^^(vʹʹ = 1) transi^ons of vibra^onally excited molecular oxygen, according to some embodiments.

[0028] Figure C1 schema^cally depicts a measured two-color (2 + 1ʹ) REMPI spectra of the rela^vely isolated 3dπ^Σ^^(0) (vʹ = 0) ←X^Σ^^(vʹ’ = 0, 1) Rydberg transi^ons of O2 compared to labelled spectral simula^ons, for example, PGOPHER (reference (B48)) simula^ons, according to some embodiments.

[0029] Figure C2 schema^cally depicts measured two-color (2 + 1ʹ) REMPI spectra of the 3dπ^Σ^^(0) (vʹ = 0) ←X^Σ^^(vʹ’ = 0) Rydberg transi^on of O2 (black trace) compared to spectral simula^ons (blue, red, and with increasing values of the upper state spin-spin coupling constant (λs−s). The λs−s signs are with the^Σ^^states lying below the^Σ^^states (reference 37B), according to some embodiments. In some examples, the values were set empirically, predominantly based on the bestfit to the cold spectra, where the electronic bands are beQer separated.

[0030] Figure D1 schema^cally depicts two-color (2 + 1ʹ) REMPI spectra of the 3d Rydberg complex of molecular oxygen, according to some embodiments. In the example shown, the black trace is the ioniza^on signal of jet-cooled O2 at ∼5 [K] ionized by ∼760 [nm] aSer tunable two-photon ultraviolet excita^on, the green trace is a mass-gated signal of atomic oxygen showing only two features at the 3dπ ^Σ^^(vʹ = 1) states. In the example, the inset shows an enlarged por^on of the mass-gated O signal.

[0031] Figure D2 schema^cally depicts: One-color (2 + 1) REMPI spectra of the C 3sσ3Πg(vʹ = 2)← X ^Σ^^F2 (leS) and F3 (right) transi^ons at various laser powers, according to some embodiments. In the illustrated example, the calculated s^ck spectrum is taken from Wiederkehr et al. (reference A2). In the example shown, the experimental spectrum is only par^ally rota^onally resolved at low laser power and unresolved at higher power where the signal is much stronger. In the illustrated example, the baselines are not shiSed, displaying the increase in non-resonant signal. The inset shows the plateau in signal for pulse energies above ∼20 [mJ]. DETAILED DESCRIPTION

[0032] The unique and ubiquitous chemistry of molecular oxygen, resul^ng from its biradical electronic structure, creates severe challenges for spectroscopic detec^on.

[0033] Addi^onally, the excita^on and ioniza^on of molecular oxygen via one color REMPI schemes struggle with achieving accurate and sensi^ve result, descrip^ve of the molecular oxygen fully rota^onally resolved spectra.

[0034] Aspects of the present disclosure pertain to a new spectroscopic detec^on scheme for molecular oxygen that achieves roughly two orders of magnitude higher sensi^vity for fully rota^onally resolved spectra than the current state of the art by employing a two-color (2 + 1’) REMPI scheme.

[0035] An addi^onal aspect of the present disclosure pertains to an excita^on, relaxa^on, and / or ioniza^on scheme, which may be facilitated by employing a radia^on regime configured to impinge upon the molecular oxygen resul^ng in photoioniza^on of the molecular oxygen.

[0036] Previously, mul^ple REMPI schemes have been employed with the aim of achieving photoioniza^on / photodissocia^on of the molecular oxygen. For example, one-color (2 + 1) REMPI. Since molecular oxygen possesses no strong allowed transi^ons at wavelengths longer than the vacuum ultraviolet (VUV), most schemes are based on two photons within the range of ultraviolet (UV) wavelength (WL), which mapped many molecular oxygen Rydberg states.

[0037] In some examples, the term “within a wavelength range”, as used herein, may also encompass the meaning of the terms “having a WL range” or “of the WL range”.

[0038] Unfortunately, the excited states suitable for one-color REMPI typically suffer from one or more drawbacks, including predissocia^on, broad linewidths, or low excita^on cross-sec^ons, which pose challenges for detec^on schemes of molecular oxygen in terms of efficiency and state selec^vity.

[0039] Embodiments of the present disclosure pertain to systems and methods that may be configured for two-color REMPI scheme for molecular oxygen, which may deliver molecular oxygen ioniza^on and / or state-selec^ve detec^on capabili^es with significantly improved sensi^vity being apparent when comparing scans covering the 3d Rydberg state spectral region, independent of the intermediate state, of the proposed two-color REMPI scheme, for example (2 + 1') REMPI, rela^ve to one-color REMPI, for example (2 + 1) REMPI.

[0040] Accordingly, in some embodiments of the systems and methods disclosed herein may be configured for two-color (2 + 1') REMPI scheme excites a 3d Rydberg state, which may u^lize at least, first electromagne^c (EM) radia^on that may be within or of afirst WL range, for example, UV WL range, adapted to facilitate excita^on of the molecular oxygen from, for example, an ini^al ground state to an intermediate excited state; and

[0041] at least one, addi^onal, second EM radia^on that may be within or of a second WL range, for example, infrared (IR) and / or visible (VIS) light WL range and / or UVA adapted for absorp^on to ionize molecular oxygen, e.g., (slightly) above the threshold of an ioniza^on state. The at least onefirst and the at least one second WL ranges may be different WL ranges.

[0042] In some examples, thefirst EM radia^on comprises at least one photon; the second EM radia^on comprises at least one photon; and the third radia^on comprises at least one photon.

[0043] The term “state” may, for example, refer to the following: condi^on, configura^on, posi^on, and / or orienta^on of various subatomic par^cles at a specific point in ^me. Moreover, the state of the subatomic par^cles may be descrip^ve of the energy, posi^on, momentum, and / or other quantum mechanical characteris^cs of the subatomic par^cles involved.

[0044] In some examples, the subatomic par^cle state may refer to one of the following energy states of the molecular oxygen:

[0045] ground state, which may be associated with the lowest and most stable energy level of molecular oxygen prior to any transforma^on ini^ated by the outpuQed laser light; and

[0046] vibra^onally excited state, which may refer to the state of the molecular oxygen aSer it had absorbed energy, for example, from thefirst EM radia^on, causing the molecular oxygen to oscillate about an equilibrium posi^on at a higher energy level than the ground state; and

[0047] virtual state, which may refer to a transient energy state that exists momentarily during a quantum mechanical process resul^ng in an intermediate state of the molecular oxygen during a transi^on between two sta^onary energy levels; and

[0048] resonant excited state, which may refer to the molecular oxygen excita^on to a higher energy level that may match the energy of the outpuQed photon and / or EM radia^onfield, resul^ng in a resonance between the molecular oxygen and the laser source, allowing efficient energy absorp^on; and

[0049] Rydberg state, which may refer to a highly excited state of molecular oxygen where at least one electron may be promoted to exceedingly high energy levels corresponding to a large principal quantum number, rela^ve to the previously men^oned state, e.g. ground state, vibra^onally excited state, virtual state, and / or resonant excited state

[0050] It is noted that the expressions “outpu[ng EM radia^on”, “outpu[ng laser”, “outpu[ng laser light” as well as gramma^cal varia^ons thereof, may encompass the meaning of the expressions “emi[ng EM radia^on”, “emi[ng laser”, “emi[ng laser light”.

[0051] In some examples, Rydberg state of the molecular oxygen may relate to subatomic par^cles states which may be characterized by large atomic radii and / or increased suscep^bility to ioniza^on.

[0052] In some examples, the subatomic par^cle state may further refer to an ioniza^on state, which may relate to sufficient energy absorp^on of the molecular oxygen resul^ng in the loss of at least one electron (ionized), thus the energy absorp^on may cause the molecular oxygen to be electrically charged, e.g., ion.

[0053] Addi^onally, and / or alterna^vely, the ioniza^on state may be referenced across the present disclosure in rela^on to an ioniza^on threshold, e.g., ioniza^on limit.

[0054] In some embodiment, the disclosed system and method may be configured to reach and / or exceed the ioniza^on threshold facilita^ng ioniza^on of the molecular oxygen. Namely, surpassing the ioniza^on limit causing the molecular oxygen to have a non-neutral electric charge.

[0055] In some embodiments, the system may have a laser arrangement configured for execu^ng two- color (2 + 1’) REMPI process of molecular oxygen.

[0056] In some embodiments, the system may have a laser arrangement configured for execu^ng [(1 + 1’) + 1’’] REMPI process of molecular oxygen, which may comprise, for example, at least one laser source configurable to output a laser pulse regime having a plurality of wavelengths (WLs) comprising:

[0057] afirst EM radia^on that is within the UV WL range; and

[0058] a second EM radia^on having a different WL from thefirst EM radia^on, wherein thefirst and second EM radia^on is adapted to facilitate excita^on of the molecular oxygen; and

[0059] a third EM radia^on that is within the infrared (IR) and / or visible light WL range and / or UVA adapted to facilitate ioniza^on of the molecular oxygen.

[0060] Is some embodiments, the laser arrangement may comprise at least one laser source configurable to output a laser pulse regime having a plurality of WLs, which may be facilitated to impinge at leastfirst EM radia^on comprising, for example, two photons, which may be within thefirst WL range; and at least second, addi^onal, EM radia^on comprising, for example, a single photon, which may be within the second WL range.

[0061] In some embodiments, thefirst EM radia^on and / or the least, addi^onal, second EM radia^on ini^ates a transforma^on of the molecular oxygen quantum mechanical characteris^cs of molecular oxygen.

[0062] Embodiments of the system may comprise, for example, a laser source configurable to output a laser pulse regime having plurality of WLs, which may be facilitated to impinge, for example, afirst EM radia^on comprising, for example, one photon, which may be within thefirst WL range; and a second EM radia^on comprising, for example, one photon, which may be within the second WL range, and an addi^onal, third EM radia^on comprising, for example, one photon, which may be within the third WL range. The third WL range may be different from thefirst and / or the second WL range.

[0063] In some embodiments, thefirst and second photons, which are within thefirst and second WL range, respec^vely, may be configured to excite the molecular oxygen, for example, from a ground state to an intermediate excited state. Complementary, the third photon, which is within the third WL range, may be configured to excite the molecular oxygen, for example, above the ioniza^on state threshold.

[0064] The term “laser pulse regime” may refer to, for example, one of the following parameters adapted to modulate the emission of EM radia^on by, separately or in any combina^on:

[0065] dura^on of the laser pulse, which may be descrip^ve of the temporal width of the pulse;

[0066] coherence, which may be descrip^ve of temporal and / or spa^al coherence corresponding to consistency of the phase across the pulse dura^on and / or the spa^al boundary of the beam, respec^vely; and

[0067] carried energy by the pulse, which may be descrip^ve of the transmiQed energy by the EM radia^on adapted to induce, for example, excita^on, relaxa^on, and / or ioniza^on in the molecular oxygen; and

[0068] energyfluence, which may be descrip^ve of energy per unit area delivered by the pulse; and

[0069] intensity, e.g., irradiance, which may be descrip^ve of power per area delivered by the pulse; and

[0070] peak power of the pulse, which may be descrip^ve of maximum instantaneous power within the pulse; and

[0071] pulse repe^^on rate, e.g., the frequency at which the pulse may be output from the at least one laser source; and

[0072] pulse WL, e.g., the central WL of the laser pulse; and

[0073] pulse bandwidth, e.g., spectral width, which may be descrip^ve of the range of the WL within the pulse; and

[0074] chirp, which may be descrip^ve varia^on of the pulse frequency over ^me configured, for example, for pulse compression and / or temporal shaping; and

[0075] beam profile, e.g., spa^al mode which may be descrip^ve of the spa^al distribu^on of the beam intensity; and

[0076] pulse shape, which may be descrip^ve of the temporal intensity profile of the pulse; and

[0077] beam divergence, which may be descrip^ve of the angular spread of the laser beam as it propagates; and

[0078] polariza^on state, which may be descrip^ve of the orienta^on of the EMfield vectors, e.g., linear, circular, ellip^cal; and / or

[0079] focus spot size, which may be descrip^ve of the diameter of the laser beam when focused on the molecular oxygen.

[0080] In some embodiments, laser pulse regime may comprise nonlinear effects, which may relate to, for example, the following effects:

[0081] self-focusing;

[0082] self-phase modula^on (SPM); and / or

[0083] mul^-photon absorp^on.

[0084] In some embodiments, frequency-mixing processes may comprise, for example, the following, separately or in any combina^on:

[0085] second-harmonic genera^on (SHG); and

[0086] third-harmonic genera^on (THG); and

[0087] high-harmonic genera^on (HHG); and

[0088] sum-frequency genera^on (SFG); and

[0089] difference-frequency genera^on (DFG); and

[0090] op^cal parametric amplifica^on (OPA); and

[0091] op^cal parametric oscilla^on (OPO); and / or

[0092] op^cal parametric genera^on (OPG).

[0093] The above examples of non-linear effects should by no means be construed as limi^ng, thus, the laser pulse regime may comprise addi^onal nonlinear effects.

[0094] Aspects of the present disclosure may relate to a system which may facilitate the emission of, for example, afirst EM radia^on, second EM radia^on, and / or third, addi^onal, EM radia^on configured to ini^ate a transforma^on in the molecular oxygen characteris^cs by execu^ng a photoioniza^on scheme of molecular oxygen comprising resonance-enhanced mul^-photon ioniza^on, for example (2 + 1’ REMPI) and / or [(1 + 1’) + 1’’] REMPI.

[0095] The term “transforma^on” may refer to the transforma^on of the molecular oxygen quantum mechanical characteris^cs which may be ini^ated by the propagated radia^on impinged upon the molecular oxygen.

[0096] Addi^onally, and / or alternately, the term ”transforma^on” may relate to changes within the molecular oxygen resul^ng from, for example, a photoioniza^on scheme, which may relate to the process facilita^ng an electron transi^on by the interac^on of, for example, one photon with the molecular oxygen.

[0097] In some embodiments, the photoioniza^on may comprise sequenced excita^ons and / or relaxa^ons of molecular oxygen.

[0098] Furthermore, the term “transforma^on” may refer to the molecular oxygen velocity, direc^onality, and / or overall trajectory of the molecular oxygen.

[0099] The term “quantum mechanical characteris^cs” may refer to the molecular oxygen quantum state, which may relate to, for example, one of the following:

[0100] principal quantum number of the molecular oxygen;

[0101] angular momentum quantum number of the molecular oxygen;

[0102] magne^c quantum number of the molecular oxygen;

[0103] spin quantum number of the molecular oxygen; and / or

[0104] any characteris^c of the electronic structure of the molecular oxygen, which may include rota^onal states, vibra^onal modes, and / or electronic states of the molecular oxygen.

[0105] The term “quantum state-resolved informa^on" may refer to data descrip^ve of the dynamics of the molecular oxygen interac^on with the impinged EM radia^on, for example:

[0106] quantum state of the molecular oxygen comprising, for example, energy levels, spin states and / or any addi^onal data descrip^ve of oxygen quantum numbers;

[0107] rota^onal states of the molecular oxygen;

[0108] vibra^onal modes of the molecular oxygen;

[0109] transla^onal energy of the molecular oxygen;

[0110] scaQering angles of the molecular oxygen; and / or

[0111] reac^on cross-sec^ons of the molecular oxygen.

[0112] In some embodiments, the system may be configured for acquiring quantum state-resolved informa^on over a broad spectral range.

[0113] In some embodiments, the laser arrangement may further comprise an op^cal arrangement, which in any combina^on with the at least one laser source, may be configured for facilita^ng tempo- spa^al overlapping of thefirst EM radia^on and the addi^onal, second EM radia^on, which may allow two-color (2 + 1’) REMPI based ioniza^on of molecular oxygen.

[0114] In some embodiments, the tempo-spa^al overlapping may be of thefirst, second and third EM radia^on, which may allow three-color [(1 + 1’)+1 ’’] REMPI based ioniza^on of molecular oxygen.

[0115] In some embodiments, the laser source may comprise, for example, one of the following: direct laser lasing sources; laser sources generated by nonlinear op^cal methods.

[0116] In some embodiments, the laser source may be one of the following: a non-tunable laser, a tunable laser, a solid-state laser; a liquid-state laser; a gaseous-state laser; a semiconductor laser; a metal vapor laser; afiber laser; a quantum cascade laser; an excimer laser; and / or any combina^on of the aforesaid.

[0117] In some embodiments, the op^cal arrangement may comprise at least one energy densifier configured for adjus^ng the propagated energy to be transferred by, for example, thefirst EM radia^on and addi^onal, second EM radia^on, which may be intersect with (also: be incident onto) the molecular oxygen.

[0118] In some embodiments, the energy densifier may comprise separately or in any combina^on, for example, one of the following: a lens system; a mirror system; a reflector system; a waveguide system; a laser resonator; and / or a collimator adapted to receive EM radia^on in the range of thefirst and / or second EM radia^on and facilitate densifying the energy carried by each EM radia^on.

[0119] In some embodiments, the lens system may comprise, for example, at least one of the following, separately or in any combina^on: plano-convex lenses, doble-convex lenses, plano-concave lenses, doble-concave lenses, plano-convex cylindrical lenses, plano-concave cylindrical lenses, drum lenses, ball lenses, posi^ve achroma^c lenses, nega^ve achroma^c lenses, aspherical lenses and / or alike.

[0120] In some embodiments, the lens system may further comprise, for example, a laser spli[ng elements, e.g. laser beamspliQer cube, lasers windows, and alike

[0121] In some embodiments, the mirror system may comprise, for example, at least one of the following, separately or in any combina^on: dielectric mirrors, dispersive mirrors, chirped mirrors, super mirrors, metal-coated mirrors, and alike.

[0122] In some embodiments, the reflector system may comprise, for example, at least one of the following, separately or in any combina^on: diffrac^on gra^ng, prism retroreflectors, Cassegrain reflectors, photonic-crystals, diffuse reflectors,fiber-op^c reflectors, and alike.

[0123] In some embodiments, the waveguide system may comprise a spa^ally inhomogeneous structure configured for guiding the EM radia^on by, for example, by restric^ng the spa^al boundaries in which the EM radia^on may propagate.

[0124] In some embodiments, the waveguide system may comprise one dimensional and / or two- dimensional waveguides.

[0125] Addi^onally, and / or alterna^vely, the waveguide system may comprise, for example, at least one of the following, separately or in any combina^on: laser waveplates, laser polarizers, laserfilters, laser beam expanders, and alike.

[0126] In some embodiments, laser resonators may comprise, for example, at least one of the following, separately or in any combina^on: plane parallel resonators, concentric (spherical) resonators, confocal resonators, generalized spherical resonators, ring resonators, or alike, which may be configured within a stable and / or unstable resonator arrangement.

[0127] The above examples should by no means be construed in a limi^ng manner, addi^onal cons^tuents may comprise the energy densifier. Moreover, each of the above-men^oned cons^tuents may be comprised of addi^onal examples for its respec^ve implementa^on.

[0128] In some embodiments, the system may be configured for the following examples, which may be implemented separately or in any combina^on:

[0129] decelera^ng a supersonic beam of molecular oxygen; and

[0130] trapping molecular oxygen; and

[0131] detec^ng molecular oxygen; and

[0132] igni^ng fuel for combus^on by an ionized molecular oxygen current; and

[0133] characterizing and measuring supersonic and hypersonicflows by u^lizing molecular oxygen Resonantly Ionized Photoemission Thermometry (RIPT) technique; and

[0134] measuring molecular oxygen rota^onal temperature by coherent microwave Rayleigh scaQering.

[0135] The above examples should by no means be construed in a limi^ng maQer, addi^onal examples for implemen^ng the disclosed laser arrangement and / or system and / or system may be u^lized, for example in the following researchfields: plasma research; atmospheric chemistry research; surface scaQering; astrochemistry research; or alike.

[0136] It should be noted that addi^onal examples may be directed at implemen^ng the disclosed laser arrangement allowing the u^liza^on of ioniza^on of molecular oxygen in a variety of different applica^ons. Addi^onally, and / or alterna^vely, further examples may be directed at implemen^ng the system for detec^on of molecular oxygen within variousfields and / or applica^ons.

[0137] Further reference is now made to the u^liza^on of the system for detec^ng molecular oxygen, for example, the system may be configured for detec^ng molecular oxygen, may comprise the following:

[0138] a mass spectrometer having a reflectron configured for measuring mass-to-charged ra^o by applying ^me-of-flight mass-spectrometry (TOFMS) which u^lizes a generated electricfield to manipulate the ionized molecular oxygen trajectory; and

[0139] a preamplifier configured for receiving mass spectrometer molecular oxygen output and (e.g., subsequently) amplifies the output prior to be fed into the monitor; and

[0140] a monitor comprising an oscilloscope operable for recording mass gated signals, which are the resultant amplified output signal received from the preamplifier.

[0141] In some embodiments, the reflectron may be a single-stage reflectron, a dual-stage reflectron, a gridless reflectron, and / or otherwise, a different type of TOFMS may be u^lized within the detec^on of the ionized molecular oxygen. In some examples, detec^on may be realized by a pair of electrodes.

[0142] The above detec^on scheme should by no means be construed in a limi^ng manner, addi^onal detec^on schemes may be employed.

[0143] Reference is now made to FIG. 1. A laser arrangement 1000 may be configured for execute a two-color REMPI 2030 scheme for molecular oxygen may comprise laser source 1100 which may be coupled with an op^cal arrangement 1200 having energy densifier 1210 capabili^es.

[0144] In some embodiments, laser arrangement 1000 may be configured for execute a two-color REMPI scheme 2030 for molecular oxygen by u^lizing a laser pulse regime 1220, which may generate a first EM radia^on within afirst wavelength ^^^and a second EM radia^on within a second wavelength ^^^, to interact with the molecular oxygen.

[0145] In some embodiments, laser arrangement 1000 may be configured for execute a two-color REMPI scheme 2030 for molecular oxygen adapt to excite the ground state 2130 by a photon having a first wavelength ^^^to afirst intermediate state 2230.

[0146] Op^onally subsequently, an addi^onal photon having afirst wavelength ^^^, excites the molecular oxygen from afirst intermediate state 2230 to a second intermediate state 2330.

[0147] Thus, a two-photon transi^on may be achieved, namely transi^ons from ground state 2130 to a first intermediate state 2230, and then aSer to a second intermediate state 2330.

[0148] Next, a photon having a second wavelength ^^^may excite the molecular oxygen from a second intermediate state 2330 to exceed the ioniza^on threshold 2430.

[0149] Thus, an (e.g., dis^nct) third photon adapted for ionizing the molecular oxygen may facilitate the transfer of energy sufficient for exceeding the ioniza^on threshold 2430.

[0150] Reference is now made to FIG.2. According to some embodiments, laser arrangement 1000 may comprise laser source 1100 which may be coupled with an op^cal arrangement 1200 having energy densifier 1210 capabili^es, which separate from or in combina^on with the op^cal arrangement 1200 may facilitate the genera^on of a laser pulse regime 1220.

[0151] In some embodiments, laser arrangement 1000 genera^ng a laser pulse regime 1220, which may comprise afirst EM radia^on within afirst wavelength ^^^and a second EM radia^on within a second wavelength ^^^, to interact, for example, with the molecular oxygen by light-maQer interac^on 1410 in a chamber 1400. Where appropriate, the expressions “chamber” may also encompass the meaning of the term “collision chamber”.

[0152] In some embodiments, a driving system 1300 may be configured to drive oxygen gas molecules by supersonic expansion into a molecular beam (MB) 1310. Thus, enabling the light-maQer interac^on 1410 of the molecular oxygen with at least one photon, in chamber 1400.

[0153] In some embodiments, light-maQer interac^on 1410 may provoke the ioniza^on of the molecular oxygen by imposing a photoioniza^on scheme upon the molecular beam 1310 generated by the driving system 1300.

[0154] In some embodiments, chamber 1400, e.g. dynamic reac^on cell (DCR), may comprise a chamber configured for receiving a pulsed laser beam generated in accordance with laser pulse regime 1220, and molecular beam 1310, allowing for light-maQer interac^on 1410.

[0155] Reference is now made to FIG.3. An example of molecular oxygen detec^on scheme 3000 may comprise the following steps:

[0156] Driving oxygen gas molecules by supersonic expansion into a MB (block 3100).

[0157] Ini^a^ng interac^on within the chamber between the MB and the pulsed laser produced in compliance with the pulsed laser regime, resul^ng in the transforma^on of the MB quantum mechanical characteris^cs (block 3200).

[0158] Accordingly, thefirst electromagne^c (EM) radia^on within the UV WL range was adapted to facilitate two-photons excita^on of the molecular oxygen (block 3210).

[0159] Furthermore, an addi^onal, second, EM radia^on within the infrared (IR) and / or visible light WL range and / or UVA adapted to facilitate single photon excita^on configured to exceed the ioniza^on threshold of the molecular oxygen (block 3220).

[0160] Thefirst example detec^on scheme 3000 may further comprise (e.g., subsequently) detec^ng molecular oxygen by feeding it into a detec^on system configured for providing an output signal by manipula^ng the ionized MB trajectory and amplifying it (block 3300).

[0161] Finally, monitoring the output signal generated by the detec^on system (block 3400) may be achieved.

[0162] Reference is now made to FIG.4. A system 4000 for ionizing molecular oxygen may comprise, for example, laser arrangement 1000, MB driving system 1300, and / or a chamber 1400.

[0163] MB driving system 1300 may comprise, for example:

[0164] a pulsed valve 1310 configured for driving oxygen gas molecules by supersonic expansion into a MB; and

[0165] afirst skimmer 1320 and a second skimmer 1330, which are configured for collima^ng the pulsed supersonic molecular beam.

[0166] In some embodiments, MB driving system 3000 may exhaust a collimated beam of molecular oxygen, which may spread minimally with very few collisions between the oxygen par^cles as it is discharged into the chamber 1400 maintaining, approximately, a parallel trajectory of the oxygen par^cles moving at supersonic velocity.

[0167] In some embodiments, thefirst skimmer 1320 may have an expending conic shape smaller rela^ve to the second skimmer 1330, which may have an expending conic shape and / or a cylindrical shape.

[0168] In some embodiments, the discharged supersonic pulsed MB may intersect with a laser light in chamber 1400.

[0169] It is noted that expressions “supersonic pulsed MB”, “molecular oxygen” and / or any gramma^cal varia^ons thereof may be used interchangeably.

[0170] In some embodiments, the intersec^on between the molecular oxygen (MB) and the laser light may be approximately perpendicular. Otherwise, any intersec^on angle (not shown) may accommodate the intersec^on between the molecular oxygen and the laser light.

[0171] In some embodiments, the light laser may have mul^ple WLs, for example, afirst electromagne^c (EM) radia^on within or having afirst WL range, e.g., ^^^, may be adapted to cause two-photon-based excita^on of the molecular oxygen into a (e.g., dis^nct) excited state.

[0172] Addi^onally, a second EM radia^on that is within or having a second WL range, e.g., ^^^, may be adapted to cause ioniza^on of the molecular oxygen from the (e.g., dis^nct) excited

[0173] In some embodiments, the laser light may be generated by a laser arrangement 1000, which may comprise, for example, the following:

[0174] afirst laser source 1110, which may generate light within, for example, the UV WL; and

[0175] a second laser source 1120, which may generate light within, for example, the VIS WL.

[0176] In some embodiments, the laser arrangement 1000 may further comprise an op^cal arrangement 1200 which may be configured for facilita^ng tempo-spa^al overlapping of thefirst EM radia^on generated byfirst laser source 1110 with the addi^onal, second EM radia^on generated by second laser source 1120.

[0177] In some embodiments, op^cal arrangement 1200 may comprise afirst energy densifier 1211 and a second energy densifier 1212 configured for adjus^ng the propagated energy to be transferred by, for example, thefirst EM radia^on, ^^^, and the addi^onal, second EM radia^on, ^^^, respec^vely.

[0178] In some embodiments, laser arrangement 1000 may further comprise a frequency doubled pulse pump 1001 and / or a delay generator 1002 which may be configured to contribute the adjustment of the propagated energy to be transferred by, for example, thefirst EM radia^on, ^^^, and the addi^onal, second EM radia^on, ^^^.

[0179] In some embodiments, the frequency doubled pulse pump 1001 may refer to the phenomenon of frequency doubling, in which an input, e.g., pump, wave may generate another wave with twice the op^cal frequency, i.e., half the vacuum WL, in the medium. In some examples, the terms “frequency doubling” and “second-harmonic genera^on” may be used interchangeably.

[0180] In some embodiments, the delay generator 1002 may interchangeably refer to “pulse delay generator” and / or “digital delay generator”, which may be configured to provide defined pulses at repe^^on rates within a precise range.

[0181] Further reference is made to FIG.4. Detec^on System 1500 configured for detec^ng molecular oxygen may comprise, for example: ^me-of-flight mass-spectrometry (TOFMS) chamber 1510 u^lizing electricfields to manipulate the ionized molecular oxygen trajectory.

[0182] In some embodiments, the detec^on System 1500 may further comprise a preamplifier 1520 configured for receiving mass spectrometer molecular oxygen output and (e.g., subsequently) then amplify the molecular oxygen output prior to the feed into monitor 1600.

[0183] In some embodiments, monitor 1600 may comprise an oscilloscope which may be operable for recording mass gated signals.

[0184] According to some embodiments, mass gated signals may be the resultant amplified output signal received from the preamplifier 1520.

[0185] Reference is now made to FIG. 5. Addi^onal example of molecular oxygen detec^on scheme 5000 may comprise the following steps:

[0186] driving the gases to be detected in supersonic expansion into a molecular beam (block 5100); and

[0187] discharging the MB into a chamber adapted to facilitate about 90-degree intersec^on with a pulsed laser ejected from a laser source (block 5200); and

[0188] exci^ng the MB by at leastfirst pulsed EM radia^on and simultaneously or subsequently ionizing the MB by at least second pulsed EM radia^on (block 5300); and

[0189] detec^ng the product ions in a TOFMS chamber, for example, the detec^on of the product ions may be executed by exposing the product ions to an electricfield (block 5400); and

[0190] amplifying the ions to be fed as mass-gated signals into the monitor, for example, the amplifica^on may be employed by a preamplifier (block 5500); and

[0191] measuring, recording and iden^fying mass-gated signals, for example, the measurement of the product ion may be facilitated by a monitor (block 5600).

[0192] The above example of a molecular oxygen detec^on scheme should not be construed in a limi^ng manner, addi^onal detec^on schemes may be applied when employing the present disclosure system and method for molecular oxygen ioniza^on.

[0193] Reference is now made to FIG. 6. A one-color two-photon excita^on photoioniza^on scheme, e.g., R2PI, 2010, is presented as a counter example to the present disclosure. R2PI 2010 may facilitate a first EM radia^on within the ^^^which facilitates transi^on from ground state 2110, surpassing excited vibra^onal state 2111, consequently, achieving resonant excited state 2210 by energy absorp^on 2410.

[0194] Op^onally subsequently, a second EM radia^on within the ^^^may facilitate the transi^on from resonant excited state 2210, surpassing Rydberg state 2211, consequently, exceeding the ioniza^on limit 2310 by energy absorp^on 2420.

[0195] It should be noted that R2PI 2010 is known to one skilled in the art to yield inferior result accuracy and sensi^vity when employed within a molecular oxygen detec^on scheme.

[0196] Reference is now made to FIG.7. A one-color two-photon excita^on plus one-photon ioniza^on scheme, e.g. (2+1) REMPI, 2020, is presented as an addi^onal counter example to the present disclosure. (2+1) REMPI 2010 may facilitate afirst EM radia^on within the ^^^which facilitates transi^on from ground state 2120, surpassing excited vibra^onal state 2121, consequently, achieving virtual state 2220 by energy absorp^on 2510.

[0197] A second EM radia^on within the ^^^may (e.g., subsequently) facilitate the transi^on from virtual state 2220 to a resonant excited state 2320 by energy absorp^on 2520.

[0198] Then a third EM radia^on within the ^^^may facilitate the transi^on from resonant excited state 2320, surpassing Rydberg state 2321, consequently, exceeding the ioniza^on limit 2420 by energy absorp^on 2530.

[0199] It should be noted that thefirst and second EM radia^on within the ^^^causing transi^on from ground state 2120, through virtual state 2220, to resonant excited state 2320 may be a result of energy absorp^on 2510 and 2520, i.e., two-photon-based excita^on of molecular oxygen.

[0200] Addi^onally, the third EM radia^on within the ^^^causing transi^on from resonant excited state 2320 to exceed the ioniza^on limit 2420 may be a result of energy absorp^on 2530, i.e., an (e.g., dis^nct) third photon-based transi^on for ionizing the molecular oxygen.

[0201] Reference is now made to FIG. 8. A two-color resonant enhanced mul^-photon ioniza^on scheme, e.g. (2+1’) REMPI, 2030, is presented as an example to the present oxygen ioniza^on system and method disclosure. (2+1’) REMPI 2030 may facilitate afirst EM radia^on within the ^^^which facilitates transi^on from ground-state 2130, surpassing excited vibra^onal state 2131, consequently, achieving virtual state 2230 by energy absorp^on 2610.

[0202] A second EM radia^on within the ^^^may (e.g., subsequently) facilitate the transi^on from virtual state 2230 to a resonant excited state 2330 by energy absorp^on 2620.

[0203] Then a third EM radia^on within the ^^^may facilitate the transi^on from resonant excited state 2330, surpassing Rydberg state 2331, consequently, exceeding the ioniza^on limit 2430 by energy absorp^on 2630.

[0204] It should be noted that thefirst and second EM radia^on within the ^^^causing transi^on from ground state 2130, through virtual state 2230, to resonant excited state 2330 may be a result of energy absorp^on 2610 and 2620, i.e. two-photon-based excita^on of molecular oxygen.

[0205] The third EM radia^on within the ^^^causing transi^on from resonant excited state 2330 to exceed the ioniza^on limit 2430 may be a result of energy absorp^on 2630, i.e., a (e.g., dis^nct) third photon-based transi^on for ionizing the molecular oxygen.

[0206] Reference is now made to FIG.9. An addi^onal example of molecular oxygen detec^on scheme 9000 may comprise the following steps:

[0207] driving oxygen gas molecules by supersonic expansion into a molecular beam, e.g., MB, (block 9100); and

[0208] ini^a^ng interac^on within the chamber between the MB and the laser light produced in accordance with a pulsed laser regime, resul^ng in a transforma^on of the MB (block 9200); and

[0209] manipula^ng the transformed MB by feeding into a detec^on apparatus configured for detec^ng and amplifying an output signal (block 9300); and

[0210] monitoring the output signal generated by the detec^on apparatus (block 9400).

[0211] In some embodiments, the transforma^on of the MB referenced in block 9200 may refer to exci^ng and / or ionizing molecular oxygen within the MB.

[0212] Moreover, the interac^on between the MB and the laser light referenced in block 9200 may further comprise, for example, the following steps:

[0213] afirst electromagne^c (EM) radia^on that is within the UV WL range adapted to facilitate single photon-based excita^on of molecular oxygen (block 9210); and

[0214] a second electromagne^c (EM) radia^on that is within the UV WL range adapted to facilitate single photon-based excita^on of molecular oxygen (block 9220); and

[0215] at least one, addi^onal, third EM radia^on that is within the infrared (IR) and / or visible light WL range and / or UVA adapted to facilitate single photon-based ioniza^on of molecular oxygen. (block 9230).

[0216] In some embodiments, block 9210 and block 9220 may refer to afirst and second EM radia^on which may be of iden^cal UV WL. Thus, block 9210 and block 9220 may be, in combina^on, descrip^ve of a two photon-based excita^on.

[0217] Accordingly, block 9210 and block 9220 followed by block 9230 may be descrip^ve of (2 + 1’) REMPI scheme, as shown in FIG.8.

[0218] Conversely, block 9210 and block 9220 may refer to afirst and second EM radia^on which may be of different UV WL. Thus, block 9210 and block 9220 may be, separately, descrip^ve of a single photon-based excita^on.

[0219] Accordingly, block 9210 and block 9220 followed by block 9230 may be descrip^ve of [(1 + 1’) + 1’’) REMPI scheme, as shown in FIG.10.

[0220] Reference is now made to FIG. 10. A three-color resonant enhanced mul^-photon ioniza^on scheme, e.g. [(1 + 1’) + 1’’] REMPI, 2040, is presented as an example to the present oxygen ioniza^on system and method disclosure. [(1+1’) +1’’] REMPI 2040 may facilitate afirst EM radia^on within the ^^^which facilitates transi^on from ground state 2140, surpassing excited vibra^onal state 2141, consequently, achieving virtual state 2240 by energy absorp^on 2710.

[0221] A second EM radia^on within the ^^^may (e.g., subsequently) facilitate the transi^on from virtual state 2240 to a resonant excited state 2340 by energy absorp^on 2720.

[0222] Then a third EM radia^on within the ^^^may facilitate the transi^on from resonant excited state 2340, surpassing Rydberg state 2341, consequently, exceeding the ioniza^on limit 2440 by energy absorp^on 2730.

[0223] It should be noted that thefirst and second EM radia^on within the ^^^causing transi^on from ground state 2140 to virtual state 2240 may be a result of energy absorp^on 2710, e.g., single-photon- based excita^on of molecular oxygen.

[0224] Op^onally subsequently, a second EM radia^on within the ^^^causing transi^on from virtual state 2240 to resonant excited state 2340 may be a result of energy absorp^on 2720, e.g., single-photon- based excita^on of molecular oxygen.

[0225] Finally, the third EM radia^on within the ^^^causing transi^on from resonant excited state 2340 to exceed the ioniza^on limit 2440 may be a result of energy absorp^on 2730, e.g., a (e.g., dis^nct) third photon-based transi^on for ionizing the molecular oxygen.

[0226] ADDITIONAL EXAMPLES

[0227] The examples provided should by no means be construed in a limi^ng manner as they are brought forth only for the purpose of accomplishing the enablement requirement of the oxygen ioniza^on system and method.

[0228] At least some of the addi^onal examples discussed below are also disclosed in: “Significantly Improved Detec^on of Molecular Oxygen by Two-Color Resonance-Enhanced Mul^photon Ioniza^on”, Itai S. Kallos, Ilana Bar, and Joshua H. Baraban, The Journal of Physical Chemistry LeQers 202415 (9), 2639-2642 DOI: 10.1021 / acs.jpcleQ.4c00141, which is incorporated herein by reference in its en^rety; and in “Resonance-enhanced mul^photon ioniza^on detec^on of vibra^onally excited O2”., Kallos IS, Benfreha K, Golibrzuch K, Zhao H, Bar I, Schäfer T, Rahinov I, Wodtke AM, Baraban JH., J Chem Phys.2025 Feb 7;162(5):051103. doi: 10.1063 / 5.0251383. PMID: 39902682, which is incorporated herein by reference in its en^rety.

[0229] METHOD EMPLOYED FOR REALIZING AN EXAMPLE EXPERIMENT

[0230] ABSTRACT

[0231] A new spectroscopic detec^on scheme is described for molecular oxygen, which may achieve roughly two orders of magnitude higher sensi^vity for fully rota^onally resolved spectra in comparison to current known shames to those skill in the art.

[0232] In some examples of the experiment, the following is reported: u^lizing a two-color (2 + 1ʹ) resonance-enhanced mul^photon ioniza^on (REMPI) via the 3d Rydberg complex yields state-selec^ve spectra with signal comparable to the intense but diffuse C 3sσ3Πg← X3Σg−(2 + 1) REMPI bands without significant satura^on or broadening.

[0233] Consequently, the resul^ng increase in sensi^vity permiQed observa^on of the very weak 3dπ1Δ2← X3Σ−gtransi^ons and is independent of the intermediate state.

[0234] Accordingly, this disclosure of advancement in ioniza^on efficiency and quantum state-selec^ve sensi^vity for O2 promotes physical and chemical studies across a wide variety offields.

[0235] EXPERIMENT DESCRIPTION

[0236] The present disclosure of the experiment may involve acquiring quantum state-resolved data, which may be necessary to reveal the physical and chemical dynamics of O2.

[0237] In some embodiments of the disclosed experiment may relate to pivotal role of molecular oxygen in chemical process on earth and beyond, for example, the subject maQer was reported in reference (A1).

[0238] Some embodiments of the experiment may be u^lized in ultracold chemistry, in which the corresponding subject maQer was reported in references (A2)-(A4).

[0239] some embodiments of the experiment may be u^lized in thefield of combus^on, in which the corresponding subject maQer was reported in references (A5) and (A6).

[0240] some embodiments of the experiment may be u^lized in thefield of plasma, in which the corresponding subject maQer was reported in references (A7) and (A8).

[0241] some embodiments of the experiment may be u^lized in thefield of atmospheric chemistry, in which the corresponding subject maQer was reported in reference (A9).

[0242] some embodiments of the experiment may be u^lized in thefield of surface scaQering, in which the corresponding subject maQer was reported in references (A10) and (A11).

[0243] some embodiments of the experiment may be u^lized in new physics searches, in which the corresponding subject maQer was reported in references (A12) and (A13).

[0244] some embodiments of the experiment may be u^lized in thefield of astrochemistry, in which the corresponding subject maQer was reported in references (A14) and (A15).

[0245] Furthermore, molecular oxygen biradical electronic structure may create challenges for spectroscopic detec^on. Thus, the present disclosure describes a novel and sensi^ve detec^on scheme allowing for fully rota^onally resolved detec^on of molecular oxygen.

[0246] In addi^on, molecular oxygen may possess no strong allowed transi^ons at WLslonger than the vacuum UV. Consequently, most molecular detec^on schemes may be based on two-photon UV.

[0247] In the following, Reference will be made to Fig.A1 for illustra^ve purposes only, Fig.A1(a), (b) and (c) elaborates upon resonance-enhanced mul^photon ioniza^on (REMPI) schemes used for molecular oxygen detec^on.

[0248] Reference is made to Fig.A1 (a). A molecular oxygen detec^on scheme employing single-color (2 + 1) resonance-enhanced mul^photon ioniza^on (REMPI) at 223-237 [nm] is shown.

[0249] Addi^onal reference is made to Fig.A1 (b). A molecular oxygen detec^on scheme employing single-color (2 + 1) resonance-enhanced mul^photon ioniza^on (REMPI) at ~287.6 [nm] is shown.

[0250] Finally, reference is made to Fig.A1 (c), descrip^ve of the disclosed two-color (2 + 1ʹ) REMPI scheme employing 223−237 [nm] with an added visible and / or infrared ionizing photon at or below 1304−771 [nm].

[0251] In some examples, one-color (2+1) REMPI schemes, which may be, currently, known shames to those skill in the art based on two-photon UV may map many O2Rydberg states.

[0252] In some examples, one-color (2+1) REMPI schemes based on two-photon UV corresponds to the subject maQer reported in references (A16) – (A25).

[0253] In some embodiments, one-color (2 + 1) REMPI schemes based on two-photon UV may be oSen augmented by ^me-of-flight mass spectrometry (TOFMS), providing mass selec^vity, high sensi^vity, and rovibra^onal resolu^on.

[0254] Unfortunately, the excited states suitable for one-color REMPI may suffer from one or more drawbacks, comprising, for example: predissocia^on, broad linewidths, and / or small excita^on cross sec^ons, which pose challenges for detec^on of O2, specifically in rela^on to efficiency and state selec^vity.

[0255] Therefore, embodiments of the present disclosure may be directed at implemen^ng the system with the aim of proposing an improved spectroscopic methods to ionize and detect O2, which may be beneficial across a variety of physical and chemicalfields, for example:

[0256] In some examples, in molecular interac^on experiments, decelera^ng and trapping atoms and / or molecules may enable studies of collisions, state selec^vity, high-density molecular quantum gases, and long-range interac^ons.

[0257] In one such study, Wiederkehr et al (reference (A2)) described the difficul^es involved in detec^ng molecular oxygen and the advantages of transi^ons to low rota^onal levels of the anomalous C 3sσ3Πg (vʹ = 2) state near 287.6 [nm] (as shown in Fig.A1 (b)) due to their rela^vely long life^mes and lower pre-dissocia^ve character.

[0258] Nonetheless, the rota^onal structure is only par^ally resolved, even when rela^vely low laser powers are employed to avoid degrading resolu^on (i.e., minimizing power broadening and AC Stark effects) at the expense of ioniza^on efficiency.

[0259] In similar contexts, a C 3sσ3Πgscheme was also u^lized by Karpov et al. (reference (A3)), who along with Akerman et al. (references (A4)) noted the need for improved detec^on schemes for molecular oxygen.

[0260] In some examples, in thefield of combus^on, laser igni^on of fuel / air mixtures via REMPI ioniza^on schemes of O2has demonstrated inherent advantages over conven^onal spark and thermal methods (reference (A26)).

[0261] In one such study, Dumitrache et al. (reference (A27)) had demonstrated improvement in electron genera^on by resonant ∼287.6 [nm] ioniza^on over non-resonant 266 [nm] increased efficiency, extended the lean limit, and reduced laser power requirements.

[0262] In some examples, in thefield of gas-surface chemistry, state-selec^ve detec^on of O2 may provide insight into processes such as oxida^on.

[0263] Nevertheless, it is oSen unmeasured or characterized by subop^mal means. For example, Nakamura and Kitajima (reference (A10)) measured only a non-resonant signal of O2at 266 [nm], while Ambaye et al. (reference (A11)) resorted to nitric oxide as a more easily detected subs^tute.

[0264] Altogether, the abovemen^oned examples make clear the broad and pressing need for enhanced spectroscopic detec^on methods for O2.

[0265] Accordingly, the present disclosure pertains to a two-color REMPI scheme for molecular oxygen, which may deliver state-selec^ve detec^on capabili^es with significantly improved sensi^vity.

[0266] Aspects of the present disclosure involve two-color (2 + 1ʹ) REMPI scheme which may excite a 3d Rydberg state using UV radia^on, followed by visible (VIS) or infrared (IR) absorp^on to ionize O2 molecules slightly above threshold, as shown in Fig.A1 (c).

[0267] In the following, Reference will be made to Fig.A2 for illustra^ve purposes only, Fig.A2(a), (b) and (c) elaborates upon Spectra recorded via resonance-enhanced mul^photon ioniza^on (REMPI) schemes of O2.

[0268] Reference is now made to Fig.A2 (a). A single-color UV (2 + 1) REMPI of the 3dπ3Σ−0 region at ∼0.7 [mJ] (red) and two-color (2 + 1ʹ) REMPI with ∼0.7 [mJ] UV pulse energy and ∼20 [mJ] visible pulse energy at 760 [nm] (blue), where the baseline of the laQer is shiSed upward for the sake of clarity.

[0269] Reference is now made to Fig.A2 (b).A (2 + 1ʹ) REMPI at a higher (∼1.4 [mJ]) UV laser pulse energy (dark cyan) compared to the blue trace from panel in Fig.A2 (a).

[0270] Reference is now made to Fig.A2 (c). A (2 + 1) REMPI of the C 3sσ3Πg(vʹ = 2) F3 state at UV pulse energies of ∼3.5 [mJ](green) and ∼25 [mJ] (dark yellow).

[0271] in some embodiments, the system of the present disclosure may achieve an improvement of two order in magnitude in sensi^vity when comparing to (2 + 1ʹ) and / or (2 + 1) REMPI scans covering the 3d Rydberg state spectral region, independent of the intermediate state; the 3dπ3Σ−0 (vʹ = 0) region previously assigned by Park et al (reference A19). is displayed in Fig.A2 (a).

[0272] Moreover, the addi^on of the intense (15−25 [mJ]) VIS beam may have minimized effect on the noise and / or non-resonant signal, which may improve the signal-to-noise ra^o (SNR).

[0273] In some embodiments, increase in the signal and / or SNR may be even more influen^al when low and / or high UVfluences fail to saturate the two-photon transi^on or result in noise and / or non-resonant ioniza^on, respec^vely.

[0274] In some embodiments, the rela^ve intensi^es follow those obtained by one-color REMPI under similar condi^ons, and / or the enhancement appears to be independent of the 1ʹ WL over a broad range.

[0275] Consequently, it may be expected that the 4s and 5s−4d Rydberg complexes that can be accessed at higher UV photon energies might exhibit similar and / or improved behavior.

[0276] Reference is now made to Fig.A3. Par^al resonance-enhanced mul^photon ioniza^on (REMPI) spectra of the 3dπ Rydberg state (vʹ = 0 or 1) is shown. The blue traces display two-color (2 + 1ʹ) REMPI signals of molecular oxygen (∼5 [K]), ionized at ∼760 [nm]. The traces are single scans (four shot average) without post-processing. The insets show the 3dπ1Δ2 ← X3Σ−g (vʹ = 0 or 1) Rydberg transi^ons, enlarged and smoothed. The green traces are digi^zed versions of the (2 + 1) REMPI results with 50−150 laser shots averaged, acquired from Park (reference A19).

[0277] To further demonstrate the efficacy of the approach, two-color (2 + 1ʹ) REMPI scans (blue trace in Fig.A3) show well-defined features corresponding to the very weak 3dπ1Δ2 ← X3Σ−g (vʹ = 0 or 1) transi^ons.

[0278] In some examples, the 3dπ1Δ2states were previously assigned by Park et al. (reference A21)., however, their detec^on and assignment had to be performed from the metastable a1Δgstate because (2 + 1) REMPI from the ground electronic state lacked the sensi^vity to confidently assign them, even with a 50−150 shot average (references (A17) -(A19)).

[0279] In some examples, in comparison, the 3dπ1Δ2state is clearly visible in a single (2 + 1ʹ) REMPI scan with only a four-shot average.

[0280] In some examples, the considerably improved performance of the (2 + 1ʹ) REMPI scheme may likely arise from the following factors, for example:

[0281] increased ioniza^on stepflux via non-resonant low-energy photons significantly improves upon the limited laser power available in the deep UV (references (A28) -(A30)), while reducing non-resonant signal, broadening, predissocia^on, and. / or dissocia^on;

[0282] ioniza^on to lower ca^on internal energies could benefit from broad autoioniza^on slightly above (∼0.8 [eV]) the ca^on ground state (references (A31) and (A32)) and / or less dissocia^ve ioniza^on.

[0283] In some embodiments, two-color REMPI signals aQributed to dissocia^ve ioniza^on may be observed only for two transi^ons the 3dπ3Σ+1(vʹ = 1) states (reference A17); these coincidences could presumably be avoided by varying the VIS photon energy.

[0284] In some examples, at ∼225 [nm], where both atomic and molecular oxygen are resonantly ionized (references (A33) and (A34)), a decrease in the O+ signal may be observed with the introduc^on of the VIS beam, which may likely be indica^ve of the en^re spectral range.

[0285] In some embodiments, an addi^onal laser beam may add undesirable experimental complexity. However, because tabletop tunable lasers may generate UV radia^on via frequency conversion, the prac^cal complica^ons of a two-color process may be mi^gated by u^lizing the laser fundamental as the second color source.

[0286] In some embodiments, this simplifica^on may be possible because the only constraint on the VIS or IR radia^on may be reaching the ioniza^on threshold.

[0287] In some embodiments, maintaining temporal and spa^al overlap may be required, especially with dispersive op^cal elements. In some examples, where signal may be the sole concern, transi^ons to the C 3sσ3Πgstates may be used; they lie near 287.6 [nm] (Fig. A2 (c)) and are more intense than the 3d Rydberg transi^ons.

[0288] Nevertheless, their broad and congested nature, which may result from predissocia^on (reference A35) oSen exacerbated by the high laser powers employed to saturate the transi^ons and maximize raw signal (Fig. A2 (c)), makes it difficult to retrieve any spectroscopic informa^on.

[0289] Addi^onally, and / or alterna^vely, broadening effects may limit their peak resonant signal. For example, under the present disclosure condi^ons, the signal for the C 3sσ3Πgstates plateaued for pulse energies of ≳20 [mJ] (Fig.D2).

[0290] In some embodiments, (2 + 1ʹ) REMPI may be applied to the C 3sσ3Πg states as well. Appropriately, the schemes may require ionizing photons below 359 [nm].

[0291] In some embodiments, higher signals should be possible using a two-color scheme; however, a highflux of 355 [nm] radia^on may be expected to produce non-resonant signal and / or broadening.

[0292] Furthermore, because available 287.6 [nm] laser sources may already saturate the transi^on the undesired involvement of conges^on will remain, thus the improvement may be less significant.

[0293] In contrast, (2 + 1ʹ) REMPI of the 3d Rydberg complex may enable the acquisi^on of rota^onally resolved spectral informa^on from many narrow features over a broad spectral range with a high SNR.

[0294] In some embodiments, the highest available deep UV pulse energy may be in the scale of ∼1.4 [mJ], (2 + 1ʹ) REMPI (dark cyan trace in Fig.A2 (b)) may exhibit signals comparable to (2 + 1) REMPI via the C 3sσ3Πgstate while remaining far from significant broadening and / or satura^on. Thus, a more powerful laser source may allow even higher (2 + 1ʹ) signals to be obtained.

[0295] In some examples, for comparison, under nominal condi^ons (∼1.1 and ∼25 [mJ] of UV and VISpulse energy, respec^vely) for both signal strength and SNR, the most intense 3dπ ^Σ^^^(2 + 1ʹ) REMPI transi^on (42636 [cm−1]) may comprise, for example:

[0296] ∼10× beQer SNR; a two order of magnitude beQer resonant to non-resonant signal ra^o; and / or a signal strength similar to that of the C 3sσ3Πg (2 + 1) REMPI scheme.

[0297] In some embodiments of the present disclosure, the disclosed example of a two-color (2 + 1ʹ) REMPI scheme may comprise, for example: significantly increased sensi^vity and / or the capability to collect quantum state-resolved informa^on over a broad spectral range.

[0298] Method:

[0299] in some embodiments, supersonic expansion of pure oxygen gas, for example, comprising 1 [bar] backing pressure, may be delivered by a pulsed valve, for example General Valve Series 9, which may have a 0.79 [mm] conic orifice.

[0300] In some embodiments, the supersonic expansion of pure oxygen gas, may be driven by, for example, an Iota One® controller with 400 [µs] opening ^me configured to generate the molecular beam (MB).

[0301] The MB passes through two skimmers 1.09 and 1.5 [mm] in diameter at 7 and 20 [cm] downstream, respec^vely.

[0302] The resul^ng MB has a low internal temperature of ~ 5 [K]. Furthermore, the two-color (2 +1') and one-color (2 + 1) REMPI using a tunable frequency-tripled pulsed dye laser (Lioptec, LiopStar-E-N with LSEH extension, 0.04 [cm] 1 linewidth, 0.65 — 1.4 [mJ]) was pumped by a frequency-doubled Nd:YAG laser (InnoLas, Spitlight 1200, 250[mJ]) for the UV beam and a tunable fundamental pulsed dye laser (Sirah, Cobra-Stretch, 0.04 [cm -1] linewidth, 15 — 25[mJ]) was pumped by another similar frequency-doubled Nd:YAG laser for the VIS beam.

[0303] The lasers produce 7 [ns] pulses at a 20 [Hz] repe^^on rate and are horizontally polarized. The respec^ve counterpropaga^ng UV and VIS beams are focused by 20 and 25.4 [cm] focal length plano- convex lenses and intersect the MB at 90°.

[0304] The two beams overlap spa^ally and temporally, and the densest and coldest MB sec^on is selected by controlling the delays between the pulsed valve and the pump laser Q-switches via a delay generator (Stanford Research, DG645).

[0305] The REMPI signal detec^on is accomplished by a reflectron TOFMS (Jordan TOF Products, C- 0726) passed through a 200x pre-amplifier (ORTEC, VT120A) and recorded by monitoring mass-gated signals on an oscilloscope.

[0306] Lis^ng of Related References for Experiment

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[0341] (A35) Sur, A.; Ramana, C. V.; Chupka, W. A.; Colson, S. D. Rydberg valence Interac^ons in the Πg states of O2. J. Chem. Phys.1986, 84, 69− 72.

[0342] The following examples are descrip^ve of valida^on and verifica^on of a molecular oxygen detec^on system and method.

[0343] SIMULATION EMPLOYED FOR COMPARISON WITH THE EXAMPLE EXPERIMENT

[0344] Abstract

[0345] Aspects of the present disclosure may comprise a rota^onally resolved spectroscopic detec^on scheme for vibra^onally excited molecular oxygen with high sensi^vity.

[0346] The present disclosure pertains to a two-color (2 + 1ʹ) resonance-enhanced mul^photon ioniza^on (REMPI) spectra of O2 in which hot bands may have been recorded for thefirst ^me via the 3dπ (vʹ = 0) ←X^Σ^^(vʹʹ = 1) Rydberg transi^ons.

[0347] constants and / or rela^ve Franck-Condon (FC) factors may have been extracted and compared with simula^ons.

[0348] Introduc^on

[0349] Molecular oxygen reacts exothermically with most compounds on Earth, ac^va^on barriers make most reac^on rates negligible under ambient condi^ons. Electronically and vibra^onally excited O2may overcome these barriers, making it highly reac^ve;

[0350] Hence, excited O2may play a crucial role in many energe^c processes spanning numerousfields, for example:

[0351] In combus^on, hot O2may be detected in combustor efficiency measurements, support for the subject maQer may be found in reference (B1). Addi^onally, hot O2in combus^on may result in reduc^on of emissions, support for the subject maQer may be found in reference (B2).

[0352] In atmospheric chemistry, excited oxygen is produced via UV photolysis of ozone, affec^ng ozone recovery, support for the subject maQer may be found in references (B3) – (B6).

[0353] in plasma science, recombina^on of atomic oxygen, collisions, and elevated temperatures can vibra^onally excite O2, support for the subject maQer may be found in references (B7) and (B8).

[0354] in surface chemistry, redox reac^ons and vibra^onal energy transfer at metal surfaces are of interest, support for the subject maQer may be found in references (B9) and (B10).A case in point are low-lying vibra^onal levels of the electronic ground state, which cannot be probed sensi^vely without vacuum ultraviolet (VUV) radia^on.

[0355] In the present disclosure, u^lizing the abovemen^oned two-color (2 + 1ʹ) ioniza^on scheme (reference (B11)), an observa^on of two-photon resonance-enhanced mul^photon ioniza^on (REMPI) spectra of vibra^onally excited O2 may have been acquired with rota^onal resolu^on via the 3dπ Rydberg states.

[0356] In some previous examples, several methods have been u^lized to detect hot molecular oxygen (reference (B12)), including Raman-Rayleigh scaQering(reference (B13)-(B16)0, laser-induced fluorescence (LIF) by ∼193, 202-228, ∼225, and ∼248 [nm] radia^on (reference (B17)-(B24)), coherent an^-Stokes Raman scaQering (CARS) (reference (B25)-(B27)), and cavity ring-down spectroscopy (CRDS) (reference (B28)).

[0357] However, these methods suffer from one or more drawbacks, including insufficient sensi^vity, use of VUV lasers to reach the Schumann-Runge bands, spectral conges^on due to many probed species, lack of fully rota^onally-resolved spectra, oSen due to the need to excite many rota^onal lines to achieve sufficient signal to noise ra^o (SNR), and difficul^es to directly probe non-equilibrium regions where radicals and other transient species drive complex chemistry. REMPI is a highly sensi^ve spectroscopic method allowing for rovibra^onal specificity (reference (B29)). REMPI can also be augmented by other methods, notably ^me-of-flight mass-spectrometry (TOFMS) for mass selec^vity (reference (B30)), microwave spectroscopy (Radar REMPI) for minimally invasive measurements (reference (B31)), temporal dynamics (reference (B32)), and recording temperatures (reference (B33)), and velocity map imaging (VMI) (reference (B34)) allowing monitoring of velocity distribu^ons.

[0358] Combining VMI with rota^onally-resolved spectra in gas phase dynamics experiments provides complete informa^on on the probed species’ internal degrees of freedom.

[0359] Many one-color REMPI studies mapped the Rydberg states of O2 (reference (B35)-(B43)); however, a REMPI spectrum of the vibra^onal hot bands of O2 was never recorded. Even when hot O2 in aflame was probed (reference (B44)), hot bands were not observed, likely due to spectral interferences and lack of sensi^vity.

[0360] Nevertheless, the recent development of two-color REMPI schemes has considerably improved sensi^vity and versa^lity (reference (B11)), allowing to record a fully rota^onally-resolved spectrum of the 3dπ (vʹ = 0)←X^Σ^^(vʹʹ = 1) transi^ons. Results were compared to simula^ons, and band origins, spectroscopic coupling constants, and rela^ve Franck-Condon (FC) factors were extracted. This new access to quantum-resolved diagnos^cs of O2 promises to shed light on many types of physical and chemical dynamics.

[0361] Methods

[0362] The study was conducted on a previously described apparatus (reference (B45)) with improved detec^on capabili^es. A VMI setup similar to the previously described (reference (B46)) was integrated into the TOFMS, allowing the measurement of velocity distribu^ons. Ions are detected via mul^channel plates (MCP, Topag MCP 56-15) found at the end of a 50 [cm]flight tube;

[0363] A P43 phosphor screen (ProxiVision) is coupled to the MCP, allowing for visualiza^on by a complimentary metal-oxide semiconductor (CMOS) camera (Basler ace acA1920-155 [mm], 1920 x 1200 [px]). Supersonic expansion of oxygen helium mixture (1 : 9) at a backing pressure of 5 [bar] was produced using a home-built pulsed valve(reference (B47)) with ∼32 [µs] opening ^me and 10 [Hz] repe^^on rate.

[0364] The gas was passed through a silicon carbide (SiC) tube (1 [mm] diameter, ∼2 [cm] length) resis^vely heated up to 1000 [K]; the temperature was monitored via a K-type thermocouple and thermal camera (CT2MHCF IR-pyrometer).

[0365] It should be noted that because SiC rapidly oxidizes under these condi^ons, hence a switch was performed to an alumina (Al2O3) tube heated by a resis^ve wire (reference (B48)), improving experimental condi^ons. The molecular beam (MB) passes through a 2 [mm] skimmer and a 2 [mm] aperture between differen^ally pumped chambers, reaching the interac^on region, where pressure increases from ∼1 × 10−9 to ∼1 × 10−8 [torr].

[0366] Ioniza^on is performed by a recently developed two-color (2 + 1ʹ) REMPI scheme(reference B11) using a tunable frequency-doubled pulsed dye laser (Sirah, Cobra-Stretch, 2.5 − 3 [mJ], ∼0.04 [cm−1]) pumped by a frequency-tripled Nd:YAG 3 laser (Con^nuum, Surelite, SLXIII-EX) as the UV excita^on source and a tunable fundamental pulsed dye laser (Sirah, Cobra-Stretch, 20 − 25 [mJ], ∼0.05 [cm−1]) pumped by an addi^onal frequency-doubled Nd:YAG laser (Spectra Physics, Quanta Ray Pro-230-10) as the visible (VIS) 744 [nm] ioniza^on source. The lasers produce ∼7.5 [ns] pulses at a 10 [Hz] repe^^on rate.

[0367] The UV and VIS beams counter-propagate and are focused by 50 [cm] focal length plano-convex lenses; beams overlap spa^ally and temporally, and the densest MB sec^on is chosen by controlling the pulsed valve and pump laser Q-switch delays via a delay generator (Stanford Research Systems, DG535).

[0368] Detec^on of the REMPI signal is accomplished by the previously described VMI setup. The scanned laser WL is constantly monitored by coupling a reflec^on into a wavemeter (HighFinesse WS7), and excita^on energy is monitored aSer the cell exit by a power meter (GentecEO Maestro).

[0369] Results and Discussion

[0370] The (2 + 1ʹ) REMPI spectra of excited O2 was recorded for many of the 3dπ (vʹ= 0)←X3Σ−g (vʹʹ= 0, 1) Rydberg transi^ons. The spectral region was chosen due to its high signal and the isolated nature of the bands, which do not overlap any ground state transi^ons.

[0371] Thus, even a small amount of excited O2 in cold-dominated oxygen mixtures can be detected, which is oSen an experimental prerequisite (reference B1). It is noted that the and are found withinthe tuning range of a single dye, hence facilita^ng the determina^on of the ( ) popula^on ra^o.

[0372] Moreover, this scheme will presumably work for higher vibra^onally excited states, of which the and are also within the tuning range of the same dye.

[0373] The spectral region was recorded using a pulsed valve and a SiC tube. The high temperature and nine observed electronic bands comprising the 3dπ Rydberg complex (reference (B37)) in the recorded spectral range result in a somewhat congested spectrum.

[0374] For reliable assignments, addi^onal scans of the 3d transi^ons were taken under differentrota^onal cooling condi^ons: without a SiC tube (very cold), a SiC tube (cold), and SiC tube heated to 1000 [K] (hot); all four spectra can be seen in Fig. B1.

[0375] The experimental spectra were normalized by UV laser power, which showed an almost quadra^c dependence across all spectra, andfiQed to PGOPHER (reference (B49)) simula^ons to extract accurate rota^onal temperatures and spectroscopic constants.

[0376] Colder spectra were used to assign bandheads, band origins, star^ng values for the rota^onal constants via combina^on differences, and spin-spin coupling constants. Rota^onal temperatures were extracted from the isolated1Σ+g (0) band (Fig. C1), resul^ng in ∼5 [K] for the coldest spectrum.

[0377] For spectra taken the SiC tube, a bimodal temperature distribu^on was observed, likely due to insufficient gasflow to fullyfill the tube and “choke” at the outlet, producing different massflow elements in thefinal outlet pulse.

[0378] Comparison to simula^ons showed 10, 25 [K] and 150, 500 [K] for the cold and hot simula^ons,respec^vely. The experimental and simulated spectral range including all observed electronic statescan be seen in Fig. B2.

[0379] Reference is now made to Fig. B1. Measured resonance-enhanced mul^photon ioniza^on (REMPI) spectra of the 3dπ (vʹ = 0)←X^Σ^^(vʹʹ = 0, 1) Rydberg two-photon transi^ons of molecular oxygen at various rota^onal temperatures are shown in four panels, (a), (b), (c), (d) corresponding to four observed spectra.

[0380] The top three panels (a, b, and c) show the band spectra, with upper electronic states labelled. The boQom panel (d) displays the hot taken at the same temperature as the trace in panel (c). Panel (d) is on a WL range than the three panels and the axis is slightly scaled for the bands to line up visually

[0381] Reference is now made to Fig. B2. Resonance-enhanced mul^photon ioniza^on (REMPI) spectra of the 3dπ (vʹ =0)←X^Σ^^(vʹʹ = 1) transi^ons of vibra^onally excited molecular oxygen are shown in three panels, (a), (b), (c).

[0382] Accordingly, the top panel (a) is an experimental REMPI spectrum of O2from the nozzle heated to 1000 [K]. The second panel (b) is a PGOPHER (reference (B48)) simula^on used to determine rota^onal temperature and constants, band origins, and coupling constants (Table 1) with 0.001 and 0.0025 [cm−1] Lorenzian and Gaussian linewidths, respec^vely. The boQom panel (c) shows, separately, each of the nine electronic states that cons^tute the 3dπ Rydberg complex in the recorded spectral range.

[0383] The (2 + 1ʹ) REMPI spectra of excited O2 was recorded for many of the 3dπ (vʹ =0)←X^Σ^^(vʹʹ = 0, 1) Rydberg transi^ons. The spectral region was chosen due to its high signal and the isolated nature of the bands, which do not overlap any ground state transi^ons.

[0384] Thus, even a small amount of excited O2 in cold-dominated oxygen mixtures can be detected, which is oSen an experimental prerequisite.

[0385] This scheme will presumably work for higher vibra^onally excited states as well. The spectral region was recorded using a pulsed valve and a SiC tube.

[0386] In some embodiments, the high temperature and nine observed electronic bands comprising the 3dπ Rydberg complex in the recorded spectral range result in a somewhat congested spectrum.

[0387] For reliable assignments, addi^onal scans of the 3dπ transi^ons were taken under different rota^onal cooling condi^ons: without a SiC tube (very cold), with a SiC tube (cold), and SiC tube heated to 1000 [K] (hot); all four spectra can be seen in Fig. B1.

[0388] The experimental spectra were normalized by UV laser power, which showed an almost quadra^c dependence across all spectra, andfiQed to PGOPHER (reference (B48)) simula^ons to extract accurate rota^onal temperatures and spectroscopic constants. Colder spectra were used to assign bandheads, band origins, star^ng values for the rota^onal constants via combina^on differences, and spin-spin coupling constants. Rota^onal temperatures were extracted from the isolated^Σ^^(0) band (Fig. C1), resul^ng in ∼5 [K] for the coldest spectrum.

[0389] For spectra taken with the SiC tube a bimodal temperature distribu^on was observed, likely due to insufficient gasflow for choking at the tube exit.

[0390] Comparison to simula^ons showed 10, 25 [K] and 150, 500 [K] for the cold and hot simula^ons, respec^vely. The experimental and simulated spectral range including all observed electronic states can be seen in B2.

[0391] It is important to note that the band origins and Bv rota^onal constants derived from the very cold and cold spectra where the electronic bands are well separated significantly constrain the hot band simula^on. This is because temperature influences the popula^on, i.e., line intensi^es, but does not affect line posi^ons.

[0392] Each electronic band has clear features and spacing (Fig. B2), which other bands cannot recreate without dras^c changes to the molecular constants. It should be noted that the centrifugal distor^on (CD) constants Dv and Hv were some^mes needed to adjust high J lines where defini^ve assignment is more challenging. Assignments for the 3dπ (vʹ = 0)←X^Σ^^(vʹʹ = 0) transi^ons via cold supersonic expansion of O2were previously performed -(B41) and (B50)); band origins and rota^onal constants were assigned with a few excep^ons.

[0393] Rota^onally hot spectra of O2allowing to refine known constants and determine addi^onal parameters (Table 1).

[0394] Spectroscopic constants for the ground state were taken from Yu et al (reference B51). All bandheads were within several wavenumbers of those reported by Yokelson et al (reference B37). However, extracted rota^onal constants did not always agree, presumably due to the small number of J states visible in the cold literature spectra.

[0395] Rota^onal constants are also compared to those tabulated by Loo et al (reference B41). and Park et al (reference B47). though only a few were reported. Spin-spin coupling constants (λs-s) were found empirically (Fig. C2). Their signs are consistent with the^Σ^^states lying energe^cally lower than the ^Σ^^; while the opposite is expected from the ππ configura^on (reference (B52)), it has been shown that in this case their order is reversed (reference ).

[0396] Rela^ve FC factors were calculated and are shown in Table 1 for each electronic state based onthe / PGOPHER simula^ons integrals. The ini^al vibra^onal popula^on is assumed as thermal,in a ∼9.6% Boltzmann popula^on of the vʹʹ = 1 level at 1000 [K]. The high rela^ve FC factors further strengthen our assump^on that higher vibra^onal hot bands should be detectable even at low popula^ons.

[0397] Table I. Rota^onal constants, origins, spin-spin couplings, and rela^ve Franck-Condon factors for the 3dπ (vʹ = 0) Rydberg states observed in this work. It has been es^mated that the uncertainty in the rela^ve FC factors may be ±0.5.

[0398] Conclusions

[0399] REMPI spectra of vibra^onal hot bands of molecular oxygen were recorded for thefirst ^me using a newly developed two-color scheme via the 3dπ Rydberg transi^ons.

[0400] New spectroscopic constants were found and known constants refined. The advantages of REMPI and coupled techniques, notably mass spectrometry and VMI, result in a broad rota^onally-resolved spectral range, good SNR, mass selec^vity, and velocity distribu^on.

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[0454] Addi^onal Suppor^ng Informa^on

[0455] Reference is made to Fig. C1. Measured two-color (2 + 1ʹ) resonance-enhanced mul^photon ioniza^on (REMPI) spectra of the rela^vely isolated 3dπ^Σ^^(0) (vʹ = 0) ←X^Σ^^(vʹʹ = 0, 1) Rydberg transi^ons of O2 compared to labelled PGOPHER in three panels, (a), (b), (c).

[0456] Accordingly, the top panel (a) shows experimental data (blue trace) taken without the silicon carbide (SiC) tube agree with a 10 [K] simula^on (black trace).

[0457] The green trace in the second panel (b) was taken with the SiC tube; the red and magenta traces are 5 and 25 [K] simula^ons, respec^vely, with the black trace showing their sum.

[0458] The orange trace in the boQom panel (c) is taken with the SiC tube heated to 1000 [K]; the dark teal and bright green traces are 150 and 500 [K] simula^ons, respec^vely, with the black trace as their sum. Spectra recorded using the SiC tube cannot be well recreated using a single temperature.

[0459] However, using two temperatures improves the agreement significantly. The feature marked by an asterisk is the Jʹʹ = Jʹ = 0 transi^ons, which can be accounted for by a small amount of very cold gas (∼5 [K]) – this recurs in most electronic bands.

[0460] Reference is made to Fig.C2. Measured two-color (2 + 1ʹ) resonance-enhanced mul^photon ioniza^on (REMPI) spectra of the 3dπ^Σ^^(0) (vʹ = 0) ←X^Σ^^(vʹʹ = 0) Rydberg transi^on of O2(black trace) compared to PGOPHER (reference (B48)) red, and green traces) with increasing values of the upper state spin-spin coupling constant (λs−s). The λs−s signs are consistent with the ^Σ^^states lying below the^Σ^^states.

[0461] The values were set empirically, predominantly based on the bestfit to the cold spectra, where the electronic bands are beQer separated.

[0462] Reference is made to Fig.D1. Two-color (2 + 1ʹ) resonance-enhanced mul^photon ioniza^on spectra of the 3d Rydberg complex of molecular oxygen. The black trace is the ioniza^on signal of jet- cooled O2 at ∼5 [K] ionized by ∼760 [nm] aSer tunable two-photon UV excita^on.

[0463] The green trace is a mass-gated signal of atomic oxygen showing only two features at the 3dπ 3Σ1+ (vʹ = 1) states. The inset shows an enlarged por^on of the mass-gated O signal.

[0464] Reference is made to Fig.D2. One-color (2 + 1) resonance-enhanced mul^photon ioniza^on spectra of the C 3sσ3Πg (vʹ = 2)← X^Σ^^F2 (leS) and F3 (right) transi^ons at various laser powers.

[0465] The calculated s^ck spectrum is taken from Wiederkehr et al. (reference (A2)). The experimental spectrum is only par^ally rota^onally resolved at low laser power and unresolved at higher power where the signal is much stronger.

[0466] The baselines are not shiSed, displaying the increase in non-resonant signal. The inset shows the plateau in signal for pulse energies above ∼20 [mJ].

[0467] Further examples:

[0468] Embodiments pertain to a laser arrangement and / or system and / or method configured to enhance an ioniza^on process of molecular oxygen by causing a two-photon-based transi^on followed by a (e.g., dis^nct) third photon-based transi^on for ionizing molecular oxygen.

[0469] In embodiments, the laser arrangement comprises: at least one laser source configured to output towards at least one oxygen molecule laser light having mul^ple WLs, as follows:

[0470] outpu[ng at least one electromagne^c (EM) radia^on within afirst WL range adapted to cause two-photon-based excita^on of the molecular oxygen into a (e.g., ) dis^nct excited state; and

[0471] outpu[ng at least one addi^onal EM radia^on that is within a second WL range adapted to cause ioniza^on from the (e.g., dis^nct) excited state of the molecular oxygen.

[0472] In embodiments, a controller is employed configured to control the at least one laser source.

[0473] In embodiments, the laser pulse regime comprises the manipula^on of at least one of the following characteris^cs of the laser pulse, separately or in any combina^on: dura^on of the laser pulse; coherence; pulse energy; energyfluence; energyflux; intensity; peak power of the pulse; pulse repe^^on rate; pulse WL; pulse bandwidth; chirp; beam profile; pulse shape; beam divergence; polariza^on state; focus spot size; and / or nonlinear effects.

[0474] In embodiments thefirst WL range is the UV WL range, and the second WL range is the infrared (IR) WL range and / or visible (VIS) light WL range and / or UVA WL range.

[0475] In embodiments, thefirst EM radia^on comprises at least two photons; and wherein the second EM radia^on comprises at least one photon.

[0476] In embodiments, the laser arrangement, system and / or method employs an op^cal arrangement, wherein the laser pulse regime of the at least one laser source and the op^cal arrangement are configured for facilita^ng temporal-spa^al overlapping of thefirst EM radia^on and the at least one, addi^onal, second EM radia^on to allow (2 + 1’) REMPI-based ioniza^on of molecular oxygen.

[0477] In embodiments, the op^cal arrangement further enhances the two-photon excita^on efficiency by supplying thefirst pair of photons in a counter-propaga^ng (“Doppler-free”) fashion to address addi^onal velocity groups within the molecular oxygen sample.

[0478] In embodiments, the op^cal arrangement comprises: at least one energy densifier configured for calibra^ng the radiant energy of thefirst EM radia^on and the at least one, addi^onal, second EM radia^on, adapted to interact with the molecular oxygen. In some examples, the energy densifier comprises at least one of the following: a lens system; a mirror system; a reflector system; a waveguide system; a laser resonator; a collimator adapted to receive EM radia^on in the range of thefirst and / or second EM radia^on and facilitate densifying the energy carried by each EM radia^on; and / or any combina^on of the aforesaid.

[0479] In embodiments, op^miza^on and / or calibra^on of radiant energy may be employed.

[0480] In embodiments, op^miza^on and / or calibra^on comprises the manipula^on of at least one of the following: total energy carried by the at least one EM radia^on of thefirst and / or second WL; radiant energy density; radiantflux; spectralflux; radiant intensity; and / or spectral intensity.

[0481] In embodiments, the at least one laser source comprises at least one of the following: direct laser lasing sources; laser sources generated by nonlinear op^cal methods; and / or any combina^on of the aforesaid.

[0482] In embodiments, the at least one laser source comprises at least one of the following: a solid- state laser; a liquid-state laser; a gaseous-state laser; a semiconductor laser; a metal vapor laser; afiber laser; a quantum cascade laser; an excimer laser; and / or any combina^on of the aforesaid.

[0483] In embodiments, the at least one laser source isfixed and / or tunable.

[0484] In embodiments, the laser arrangement, system and / or method is configured for implemen^ng [(1 + 1’) + 1’’], comprising at least one laser source configurable to output a laser pulse regime having mul^ple WLs comprising, for example, afirst electromagne^c (EM) radia^on that is within the UV WL range; and a second EM radia^on having a different WL from thefirst EM radia^on, wherein thefirst and second EM radia^ons are adapted to facilitate excita^on of the molecular oxygen; and at least one, addi^onal, third EM radia^on that is within the infrared (IR) and / or visible light WL range and / or UVA adapted to facilitate ioniza^on of the molecular oxygen.

[0485] In embodiments, the laser arrangement, system, and / or method is configured for acquiring quantum state-resolved informa^on over a broad spectral range by execu^ng an enhanced ioniza^on process of molecular oxygen comprising resonance-enhanced mul^-photon ioniza^on, for example, (2 + 1’) REMPI and / or [(1 + 1’) + 1’’] REMPI.

[0486] In embodiments, a system comprises, in addi^on to a laser arrangement, for example, one of the following a mass spectrometer having a reflectron configured for measuring mass-to-charge ra^o for ^me-of-flight mass-spectrometry (TOFMS) which u^lizes electricfields to manipulate the ionized molecular oxygen trajectory; a preamplifier configured for receiving mass spectrometer molecular oxygen output and (e.g., subsequently) amplify the output prior to the feed into the monitor; and / or a monitor.

[0487] In embodiments, the system comprises an oscilloscope operable for recording mass gated signals, which are the resultant amplified output signal received from the preamplifier.

[0488] In embodiments, the monitor comprises the oscilloscope.

[0489] In embodiments, the system comprises a chamber, a driving system of a molecular beam (MB), and / or a detec^on system. In some examples, the detec^on system comprises a TOFMS chamber and / or a pre-amplifier.

[0490] In some embodiments, a method for enhancement of an ioniza^on process of molecular oxygen by causing a two-photon-based transi^on followed by a (e.g., dis^nct) third photon-based transi^on for ionizing the molecular oxygen comprises:

[0491] outpu[ng towards at least one oxygen molecule laser light having mul^ple WLs, e.g., as follows:

[0492] outpu[ng at least one electromagne^c (EM) radia^on within afirst WL range adapted to cause two-photon-based excita^on of the molecular oxygen into a (e.g., dis^nct) excited state; and

[0493] outpu[ng at least one addi^onal EM radia^on that is within a second WL range adapted to cause ioniza^on from the (e.g., dis^nct) excited state of the molecular oxygen.

[0494] In embodiments, the method comprises controlling the at least one laser source.

[0495] In some embodiments, the method comprises manipula^ng at least one of the following characteris^cs of the laser pulse, separately or in any combina^on: dura^on of the laser pulse; coherence; pulse energy; energyfluence; energyflux; intensity; peak power of the pulse; pulse repe^^on rate; pulse WL; pulse bandwidth; chirp; beam profile; pulse shape; beam divergence; polariza^on state; focus spot size; and / or nonlinear effects.

[0496] In some embodiments, thefirst WL range is the UV WL range, and the second WL range is the infrared (IR) WL range and / or visible (VIS) light WL range and / or UVA WL range.

[0497] In some embodiments, the method comprises enhancing the two-photon excita^on efficiency by supplying thefirst pair of photons in a counter-propaga^ng (“Doppler-free”) fashion to address addi^onal velocity groups within the molecular oxygen sample.

[0498] In some embodiments, the method comprises comprising calibra^ng the radiant energy to be propagated by thefirst EM radia^on and the at least one, addi^onal, second EM radia^on, adapted to interact with the molecular oxygen.

[0499] In some embodiments, the method comprises improving the op^miza^on radiant energy, e.g., by manipula^ng at least one of the following characteris^cs of the radiant energy, separately or in any combina^on: total energy carried by the at least one EM radia^on of thefirst and / or second WL; radiant energy density; radiantflux; spectralflux; radiant intensity; and / or spectral intensity.

[0500] In some embodiments, the method comprises implemen^ng [(1 + 1’) + 1’’], by outpu[ng a laser pulse regime having mul^ple WLs. In some examples, the mul^ple WLs comprise afirst electromagne^c (EM) radia^on that is within the UV WL range; and a second EM radia^on having a different WL from the first EM radia^on, wherein thefirst and second EM radia^ons are adapted to facilitate excita^on of the molecular oxygen; and at least one, addi^onal, third EM radia^on that is within the infrared (IR) and / or visible light WL range and / or UVA adapted to facilitate ioniza^on of the molecular oxygen.

[0501] In some embodiments, the method comprises acquiring quantum state-resolved informa^on over a broad spectral range by execu^ng an enhanced ioniza^on process of molecular oxygen comprising resonance-enhanced mul^-photon ioniza^on, for example, (2 + 1’) REMPI and / or [(1 + 1’) + 1’’] REMPI.

[0502] The various features and steps discussed above, as well as other known equivalents for each such feature or step, can be mixed and matched by one of the ordinary skills in this art to perform methods in accordance with principles described herein.

[0503] Although the disclosure has been provided in the context of certain embodiments and examples, it will be understood by those skilled in the art that the disclosure extends beyond the specifically described embodiments to other alterna^ve embodiments and / or uses and obvious modifica^ons and equivalents thereof.

[0504] Accordingly, the disclosure is not intended to be limited by the specific disclosures of embodiments herein.

[0505] The term "non-transitory" is used to exclude transitory, propaga^ng signals, but to otherwise include any vola^le or non-vola^le computer memory technology suitable to the applica^on.

[0506] Addi^onally, and / or alterna^vely, the methods and / or processes disclosed herein may be implemented as a computer program that may be intangibly embodied by a computer readable signal medium.

[0507] It is noted that the term “method” may also encompass the meaning of the term “process”.

[0508] A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electrical, electro- magne^c, op^cal, or any suitable combina^on thereof.

[0509] A readable computer signal medium may be any readable computer medium that is not a non- transitory computer or machine-readable storage device and that can communicate, propagate, or transport a program for use by or in connec^on with apparatuses, systems, platorms, methods, opera^ons, and / or processes discussed herein.

[0510] The terms “non-transitory computer-readable storage device” and “non-transitory machine- readable storage device” encompasses distribu^on media, intermediate storage media, execu^on memory of a computer, and any other medium or device capable of storing for later reading by a computer program implemen^ng embodiments of a method disclosed herein.

[0511] In the discussion, unless otherwise stated, adjec^ves such as “substan^ally” and “about” that modify a condi^on or rela^onship characteris^c of a feature or features of an embodiment of the disclosure, are to be understood to mean that the condi^on or characteris^c is defined to within tolerances that are acceptable for opera^on of the embodiment for an applica^on for which it is intended.

[0512] Unless otherwise specified, the terms 'about' and / or 'close' with respect to a magnitude or a numerical value may imply to be within an inclusive range of -10% to +10% of the respec^ve magnitude or value.

[0513] It should be noted that where an embodiment refers to a condi^on of "above a threshold", this should not be construed as excluding an embodiment referring to a condi^on of "equal or above a threshold".

[0514] Analogously, where an embodiment refers to a condi^on “below a threshold”, this should not be construed as excluding an embodiment referring to a condi^on “equal or below a threshold”. It is clear that should a condi^on be interpreted as being fulfilled if the value of a given parameter is above a threshold, then the same condi^on is considered as not being fulfilled if the value of the given parameter is equal or below the given threshold.

[0515] Conversely, should a condi^on be interpreted as being fulfilled if the value of a given parameter is equal or above a threshold, then the same condi^on is considered as not being fulfilled if the value of the given parameter is below (and only below) the given threshold.

[0516] It should be understood that where the claims or specifica^on refer to "a" or "an" element and / or feature, such reference is not to be construed as there being only one of that element.

[0517] Hence, reference to “an element” or “at least one element” for instance may also encompass “one or more elements”.

[0518] As used herein the term "configuring" and / or 'adap^ng' for an objec^ve, or a varia^on thereof, implies using materials and / or components in a manner designed for and / or implemented and / or operable or opera^ve to achieve the objec^ve.

[0519] It is appreciated that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments or examples, may also be provided in any combina^on in a single embodiment.

[0520] Conversely, various features of the present disclosure, which are, for brevity, described in the context of a single embodiment, example and / or op^on, may also be provided separately or in any suitable sub-combina^on or as suitable in any other described embodiment, example, and / or op^on of the present disclosure.

[0521] Furthermore, any feature disclosed herein can be disclaimed, alone or in any combina^on of features.

[0522] Certain features described in the context of various embodiments, examples and / or op^ons are not to be considered essen^al features of those embodiments, unless the embodiment, example and / or op^on is inopera^ve without those elements.

[0523] Unless otherwise stated or applicable, the use of the expression “and / or” between the last two members of a list of op^ons for selec^on indicates that a selec^on of one or more of the listed op^ons is appropriate and may be made, and may be used interchangeably with the expressions “at least one of the following”, “any one of the following” or “one or more of the following”, followed by a lis^ng of the various op^ons.

[0524] As used herein, the phrase “A, B, C, or any combina^on of the aforesaid” should be interpreted as meaning all of the following:

[0525] (i) A or B or C or any combina^on of A, B, and C;

[0526] (ii) at least one of A, B, and C; and

[0527] (iii) A, and / or B and / or C.

[0528] This concept is illustrated for three elements (i.e., A, B, C), but extends to fewer and greater numbers of elements (e.g., A, B, C, D, etc.).

[0529] It is noted that the terms “operable to” or “opera^ve to” can encompass the meaning of the term “adapted or configured to”. In other words, a machine “operable to” or “opera^ve to” perform a task can in some embodiments, embrace a mere capability (e.g., “adapted”) to perform the func^on and, in some other embodiments, a machine that is actually made (e.g., “configured”) to perform the func^on.

[0530] Throughout this applica^on, various embodiments of this disclosure may be presented in a range format. It should be understood that the descrip^on in range format is merely for convenience and brevity and should not be construed as an inflexible limita^on on the scope of the disclosure.

[0531] Accordingly, the descrip^on of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, descrip^on of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 4, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 4 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0532] Whenever a numerical range is indicated herein, it is meant to include any cited numeral (frac^onal or integral) within the indicated range.

[0533] The phrases “ranging / ranges between” afirst indicate number and a second indicate number and “ranging / ranges from” afirst indicate number “to” a second indicate number are used herein interchangeably and are meant to include thefirst and second indicated numbers and all the frac^onal and integral numerals therebetween.

[0534] It should be appreciated that combina^ons of features disclosed in different embodiments are also included within the scope of the present disclosures.

[0535] While certain features of the disclosure have been illustrated and described herein, many modifica^ons, subs^tu^ons, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifica^ons and changes as fall within the true spirit of the disclosure.

[0536] the adjec^ve “gradually” may refer to the temporal change, which may take place over a period of ^me in small, incremental steps.

[0537] the term “con^nuously” may refer to spa^al change, which may progress steadily without stops and / or gaps.

[0538] It should be noted that the term “light” as used herein may refer to electromagne^c radia^on of any suitable WL for the purposes of the applica^ons disclosed herein. Accordingly, the term “light” should not be construed as being limited to visible light and may addi^onally or alterna^vely include non-visible radia^on such as, for example, laser light in the infrared range and UV light.

[0539] Accordingly, the term “light” should not be construed as being limited to visible light and may addi^onally or alterna^vely include non-visible radia^on such as, for example, light in the infrared range, light in the short-wave infrared range and light in the ultra-violate range. The light may be coherent, non- coherent or par^ally coherent. The light may be polarized, non-polarized or par^ally polarized.

[0540] The light may have a wide spectral width (e.g. of the range of hundreds of nanometers such as originated from a black body), the light may have a mid-spectral width (e.g. of the range of tens of nanometers such as originated from a LED) or the light may have a narrow spectral width (e.g. of the range of a few nanometers, or much less (e.g., 1 nm or less, 0.05 nm or less, or 0.01 [nm] or less), such as originated from a laser).

[0541] Moreover, the terms “light” and “EM radia^on” may herein be used interchangeably.

[0542] In some embodiments, it is appreciated that certain features of the present disclosure, which are, for clarity, may be described separately, may also be provided in any combina^on in a single embodiment.

Claims

CLAIMS What is claimed is:

1. A laser arrangement configured for enhancement of an ioniza^on process of molecular oxygen by causing a two-photon-based transi^on followed by a third photon-based transi^on for ionizing the molecular oxygen, the laser arrangement comprising: at least one laser source configured to output towards at least one oxygen molecule laser light having mul^ple wavelengths (WLs), as follows: outpu[ng at least one electromagne^c (EM) radia^on having afirst WL range adapted to cause two-photon-based excita^on of the molecular oxygen into an excited state; and outpu[ng at least one addi^onal EM radia^on having a second WL range adapted to cause ioniza^on of the molecular oxygen from the excited state.

2. The laser arrangement of claim 1, comprising a controller configured to control the at least one laser source.

3. The laser arrangement of claim 1 and / or claim 2, wherein the laser pulse regime comprises the manipula^on of at least one of the following characteris^cs of the laser pulse, separately or in any combina^on: dura^on of the laser pulse; coherence; pulse energy; energyfluence; intensity; peak power of the pulse; pulse repe^^on rate; pulse wavelength (WL); pulse bandwidth; chirp; beam profile; pulse shape; beam divergence; polariza^on state; focus spot size; and / or nonlinear effects.

4. The laser arrangement of any one or more of the preceding claims, wherein thefirst WL range is the ultraviolet (UV) WL range, and the second WL range is the infrared (IR) WL range and / or visible (VIS) light WL range and / or UVA WL range.

5. The laser arrangement of any one or more of the preceding claims, wherein thefirst EM radia^on comprises at least two photons; and wherein the second EM radia^on comprises at least one photon.

6. The laser arrangement of any one or more of the preceding claims, wherein the laser arrangement further comprises an op^cal arrangement, wherein the laser pulse regime of the at least one laser source and the op^cal arrangement are configured for facilita^ng temporal- spa^al overlapping of thefirst EM radia^on and the at least one, addi^onal, second EM radia^on to allow 2+1’ REMPI-based ioniza^on of molecular oxygen.

7. The laser arrangement of any one or more of the preceding claims, wherein the op^cal arrangement further enhances the two-photon excita^on efficiency by supplying thefirst pair of photons in a counter-propaga^ng (“Doppler-free”) fashion so as to address addi^onal velocity groups within the molecular oxygen sample.

8. The laser arrangement of any one or more of the claims 6 to 7, wherein the op^cal arrangement comprises: at least one energy densifier configured for calibra^ng radiant energy to be propagated by the first EM radia^on and the at least one, addi^onal, second EM radia^on, adapted to interact with the molecular oxygen, wherein the energy densifier comprises at least one of the following: a lens system; a mirror system a reflector system; a waveguide system; a laser resonator; a collimator adapted to receive EM radia^on in the range of thefirst and / or second EM radia^on and facilitate densifying the energy carried by each EM radia^on; and / orany combina^on of the aforesaid.

9. The laser arrangement of claim 8, wherein calibra^ng the radiant energy comprises the manipula^on of at least one of the following characteris^cs of the radiant energy, separately or in any combina^on: total energy carried by the at least one EM radia^on of thefirst and / or second WL; radiant energy density; radiantflux; spectralflux; radiant intensity; and / or spectral intensity; 10. The laser arrangement of any one or more of the preceding claims, wherein the at least one laser source comprises at least one of the following: direct laser lasing sources; laser sources generated by nonlinear op^cal methods; and / or any combina^on of the aforesaid.

11. The laser arrangement of any one or more of the preceding claims, wherein the at least one laser source is at least one of the following: a solid-state laser; a liquid-state laser; a gaseous-state laser; a semiconductor laser; a metal vapor laser;afiber laser; a quantum cascade laser; an excimer laser; and / or any combina^on of the aforesaid.

12. The laser arrangement of any one or more of the preceding claims, wherein the at least one laser source isfixed and / or tunable.

13. The laser arrangement of any one or more of previous claims, wherein the laser arrangement is configured for implemen^ng [(1 + 1’) + 1”] REMPI-based ioniza^on of molecular oxygen, comprising at least one laser source configurable to output a laser pulse regime having mul^ple wavelengths (WLs) comprising: afirst electromagne^c (EM) radia^on that is within the ultraviolet (UV) WL range; and a second EM radia^on having a different WL from thefirst EM radia^on, wherein thefirst and second EM radia^ons are adapted to facilitate excita^on of the molecular oxygen; and at least one, addi^onal, third EM radia^on that is within the infrared (IR) and / or visible light WL range and / or UVA adapted to facilitate ioniza^on of the molecular oxygen.

14. The laser arrangement of any one or more of the previous claims, adapted for acquiring quantum state-resolved informa^on over a broad spectral range by execu^ng an enhanced ioniza^on process of molecular oxygen comprising 2+1’ resonant enhanced mul^-photon ioniza^on (2+1’ REMPI) and / or [(1 + 1’) + 1”] REMPI.

15. A system, configured for the ioniza^on and / or detec^on of molecular oxygen, the system comprising: a laser arrangement, for example, according to any one or more of the preceding claims;a mass spectrometer having a reflectron configured for measuring mass-to-charge ra^o for ^me- of-flight mass-spectrometry (TOFMS) which u^lizes electricfields to manipulate the ionized molecular oxygen trajectory; a preamplifier configured for receiving mass spectrometer molecular oxygen output and amplify the output prior to the feed into the monitor; and a monitor comprising an oscilloscope operable for recording mass gated signals, which are the resultant amplified output signal received from the preamplifier.

16. A method for enhancement of an ioniza^on process of molecular oxygen by causing a two- photon-based transi^on followed by a third photon-based transi^on for ionizing the molecular oxygen, the method comprising: outpu[ng towards at least one oxygen molecule laser light having mul^ple wavelengths (WLs), as follows: outpu[ng at least one electromagne^c (EM) radia^on within afirst WL range adapted to cause two-photon-based excita^on of the molecular oxygen into a excited state; and outpu[ng at least one addi^onal EM radia^on that is within a second WL range adapted to cause ioniza^on from the excited state of the molecular oxygen.

17. The method of claim 16, comprising controlling the at least one laser source.

18. The method of claim 16 and / or 17, comprising manipula^ng at least one of the following characteris^cs of the laser pulse, separately or in any combina^on: dura^on of the laser pulse; coherence; pulse energy; energyfluence; intensity; peak power of the pulse; pulse repe^^on rate; pulse WL; pulse bandwidth; chirp; beam profile; pulse shape; beam divergence; polariza^on state; focus spot size; and / or nonlinear effects.

19. The method of any one or more of the claims 16 to 18, wherein thefirst WL range is the UV WL range, and the second WL range is the infrared (IR) WL range and / or visible (VIS) light WL range and / or UVA WL range.

20. The method of any one or more of the claims 16 to 19, wherein thefirst EM radia^on comprises at least two photons; and wherein the second EM radia^on comprises at least one photon.

21. The method of any one or more of the claims 16 to 20, wherein the laser arrangement further comprises an op^cal arrangement, wherein the laser pulse regime of the at least one laser source and the op^cal arrangement are configured for facilita^ng temporal-spa^al overlapping of the first EM radia^on and the at least one, addi^onal, second EM radia^on to allow 2+1’ REMPI- based ioniza^on of molecular oxygen.

22. The method of any one or more of the claims 16 to 21, comprising enhancing the two-photon excita^on efficiency by supplying thefirst pair of photons in a counter-propaga^ng (“Doppler- free”) fashion so as to address addi^onal velocity groups within the molecular oxygen sample.

23. The method of any one or more of the claims 16 to 22, comprising calibra^ng the radiant energy to be propagated by thefirst EM radia^on and the at least one, addi^onal, second EM radia^on, adapted to interact with the molecular oxygen.

24. The method of any one or more of the claims 16 to 23, wherein the op^miza^on of the radiant energy comprises: manipula^ng at least one of the following characteris^cs of the radiant energy, separately or in any combina^on: total energy carried by the at least one EM radia^on of thefirst and / or second WL; radiant energy density; radiantflux; spectralflux; radiant intensity; and / or spectral intensity.

25. The method of any one or more of the claims 16 to 24, comprising: implemen^ng [(1+1’)+1”], by outpu[ng a laser pulse regime having mul^ple wavelengths (WLs), the mul^ple WLs comprising: afirst electromagne^c (EM) radia^on that is within the UV WL range; and a second EM radia^on having a different WL from thefirst EM radia^on, wherein thefirst and second EM radia^ons are adapted to facilitate excita^on of the molecular oxygen; and at least one, addi^onal, third EM radia^on that is within the infrared (IR) and / or visible light WL range and / or UVA adapted to facilitate ioniza^on of the molecular oxygen.

26. The method of any one or more of the claims 16 to 25, comprising acquiring quantum state- resolved informa^on over a broad spectral range by execu^ng an enhanced ioniza^on process of molecular oxygen comprising (2 + 1’) resonant enhanced mul^-photon ioniza^on (2 + 1’ REMPI) and / or [(1 + 1’) +1”] REMPI.

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