Liquid beam photoelectron imaging device based on femtosecond vacuum ultraviolet laser pulses

Abstract

The present invention discloses a liquid beam photoelectron imaging device based on femtosecond vacuum ultraviolet laser pulses, which includes a femtosecond pump-probe optical path system, a four-wave mixing generation and transmission system, a vacuum maintenance system, a liquid beam sampling system, and a photoelectron collection and imaging detection system. The present invention combines vacuum ultraviolet laser pulses with OPA output lasers (ultraviolet to infrared bands) to achieve a time-resolved measurement function, and can not only use vacuum ultraviolet lasers as pump light, but also use vacuum ultraviolet lasers as probe light functions.

Description

Technical Field

[0001] The present invention relates to the technical field of generation of vacuum ultraviolet laser pulses and time-resolved imaging of photoelectrons in solution, and particularly relates to a liquid beam photoelectron imaging device based on femtosecond vacuum ultraviolet laser pulses. Background Art

[0002] The time-resolved function is achieved through pump-probe technology, that is, first a molecule is excited by a laser beam, and then another beam of light is used to ionize the excited molecule. By precisely controlling the optical path difference between the two beams of light, a time-resolved measurement function can be realized. Combining time resolution with photoelectron imaging technology has developed a time-resolved photoelectron imaging device, which is widely used in the study of ultrafast dynamics of molecules. Through this device, kinetic energy distribution and angular distribution information of time-resolved electrons / ions can be obtained, and then the structural changes of molecules and the whole process of molecular chemical reactions can be characterized in real time. At present, the time-resolved photoelectron imaging device has been successfully applied to the study of gas-phase sample molecules, called the time-resolved gas-phase photoelectron imaging device. However, the gas-phase photoelectron imaging device cannot study the influence of solvent molecules on solute molecules in solution. However, for life sciences, its tissues and cells are usually in a solution environment, and physiological chemical reactions also occur in the solution environment. Therefore, at the microscopic level, physiological chemical reactions of biomolecules must be affected by the external solution environment. But how to directly measure the kinetic energy distribution and angular distribution information of electrons / ions in a solution environment, and then more realistically characterize the structural changes of molecules and the whole process of molecular chemical reactions in real time in a solution environment has always been a challenge for scientists. Until recent years, researchers have developed a liquid beam photoelectron imaging spectroscopy device based on liquid beam injection technology (authorized patent number ZL 201911172966.2). This technology uses a high-pressure infusion pump to inject liquid into a vacuum chamber, and a stable-flow beam is formed within 2-3 mm from the nozzle outlet, which we call the transparent region. When light interacts with this region, molecules are ionized to generate electrons, and the electrons fly to the detector for imaging under the action of an imaging lens, so that kinetic energy information and angular distribution information of electrons in a solution environment can be obtained. Despite the technological progress, this liquid beam photoelectron imaging spectroscopy device cannot perform time-resolved measurements, and thus cannot observe the structural changes of molecules and the whole process of molecular chemical reactions in a solution environment in real time.

[0003] In addition, in the actual process, since the ionization potential of molecules is relatively high, light in the visible to infrared wavelength range cannot directly ionize them with a single photon and requires a multi-photon process. Compared with single-photon ionization, multi-photon ionization not only has a low ionization efficiency, but also, due to the existence of intermediate states, leads to a complex composition after ionization, making it sometimes difficult to assign. Additionally, when the excited state of a molecule moves along the reaction path on the potential energy surface to a lower potential energy surface, even if ultraviolet photons are used as the ionization light, the single-photon energy is not sufficient to ionize the molecules at the lower potential energy surface, and thus some or even most of the ultrafast path processes during the reaction cannot be observed. This situation often occurs in photochemical reactions such as photodissociation and photoisomerization. To solve the above problems and then achieve the tracking of the entire ultrafast process of photochemical reactions, it is necessary to introduce laser pulses in the vacuum ultraviolet wavelength range for direct single-photon ionization. Especially in many solution environments, since the binding energy of molecules is relatively high, it is very necessary to introduce vacuum ultraviolet laser pulses. In addition, by using vacuum ultraviolet laser pulses as pump light, ultrafast dynamics studies of highly excited state atoms and molecules can also be carried out. Most atoms have a high ionization energy, and the preparation of their excited states requires high-energy photons; while the electronic excited states (Rydberg, high-valence, and super-excited states) of most molecules are also much higher than the single-photon energy in the ultraviolet to infrared wavelength range, and many important photochemical reactions in nature also occur in this wavelength range. For example, the first excited state of a water molecule is a repulsive state located in the vacuum ultraviolet wavelength range (165 nm), and its predicted lifetime is less than 20 fs. The research on ultrafast vacuum ultraviolet spectroscopy related to water molecules remains a challenge due to the lack of effective experimental techniques to date.

[0004] In view of the above problems, the present invention proposes a time-resolved liquid beam photoelectron imaging device based on femtosecond vacuum ultraviolet laser pulses. Its basic principle is as follows: The 800-nm laser output by the laser is first split by the first beam splitter. The reflected light passes through an optical parametric amplifier to generate light with a wavelength of 240 - 2600 nm, and finally interacts with the transparent region of the liquid beam. The light transmitted through the first beam splitter reaches the second beam splitter, and the second beam splitter divides the light into two paths. One path of the light is frequency-doubled to 400 nm, and then the 800-nm and 400-nm lights simultaneously undergo a four-wave mixing reaction with argon to generate 160-nm laser pulses. Finally, the 160-nm light is combined with the liquid beam photoelectron imaging device. Through the displacement platform 2, the optical path difference between the 160-nm and OPA lights can be adjusted. The liquid beam photoelectron imaging device first uses a high-pressure infusion pump to eject the liquid from the nozzle to form a transparent region, then the 160-nm laser pulse acts on this transparent region, and finally the generated photoelectrons are imaged by the imaging lens of the liquid beam imaging device. By changing the optical path difference between the vacuum ultraviolet laser pulse and the OPA output light, a time-resolved liquid beam imaging device is realized, which is called a time-resolved liquid beam photoelectron imaging device based on femtosecond vacuum ultraviolet laser pulses. This time-resolved liquid beam photoelectron imaging device based on femtosecond vacuum ultraviolet laser pulses further expands the time-resolved measurement function of the liquid beam imaging energy spectrum device, and solves the problem that photons in the ultraviolet to infrared bands cannot be directly single-photon ionized in conventional experiments, so that the ultrafast process of the entire photoreaction can be tracked in real time in a solution environment. It is a truly time-resolved photoelectron imaging detection and analysis method considering the solution environment. Summary of the Invention

[0005] The object of the present invention is to provide a liquid beam photoelectron imaging device based on femtosecond vacuum ultraviolet laser pulses for the above problems existing in the prior art.

[0006] The above object of the present invention is achieved by the following technical solutions:

[0007] A liquid beam photoelectron imaging device based on femtosecond vacuum ultraviolet laser pulses includes a femtosecond laser. The femtosecond laser emits femtosecond laser, which is split by the first beam splitter into a first reflected light and a first transmitted light. The first transmitted light is split by the second beam splitter into a second reflected light and a second transmitted light. The second transmitted light sequentially passes through a BBO frequency-doubling crystal, a first optical path adjustment module, and a second focusing lens and then enters a beam combining sheet. The second reflected light sequentially passes through a half-wave plate and a first focusing lens and then enters the beam combining sheet. The combined light emitted by the beam combining sheet enters a filament formation and four-wave mixing gas cell. The light emitted by the four-wave mixing gas cell enters the first vacuum chamber through a vacuum interface. After the incident angle is adjusted by the mirror in the first vacuum chamber, it then enters the second vacuum chamber through the vacuum interface and acts on the transparent region of the liquid beam ejected from the fused quartz nozzle.

[0008] The first reflected light passes through the optical parametric amplifier and the second optical path adjustment module in sequence, and then passes through the first concave mirror and the second concave mirror in sequence to adjust the incident angle after reflection, and then enters the second vacuum cavity and acts on the transparent area of the liquid beam ejected from the fused silica nozzle.

[0009] The filament formation and four-wave mixing gas cell as described above is connected to the first mechanical pump, the first vacuum cavity is connected to the second mechanical pump, and the filament formation and four-wave mixing gas cell is also connected to the krypton gas cylinder.

[0010] A perforated plate is arranged in the second vacuum cavity as described above. A fused silica nozzle and a first cold trap are arranged on the top side wall on the left side of the perforated plate in the second vacuum cavity. A first molecular pump is arranged at the left end of the second vacuum cavity, and the first molecular pump is connected to the third mechanical pump.

[0011] A repelling electrode, an accelerating electrode and a ground electrode are arranged in sequence from left to right below the fused silica nozzle in the second vacuum cavity. A second cold trap is arranged on the side wall below the fused silica nozzle in the second vacuum cavity.

[0012] A magnetic shielding cylinder is arranged on the right side of the perforated plate in the second vacuum cavity. A second molecular pump is also arranged on the bottom side wall on the right side of the perforated plate in the second vacuum cavity, and the second molecular pump is connected to the fourth mechanical pump.

[0013] A two-dimensional position sensitive detector is arranged at the right end of the second vacuum cavity. The CCD camera and the photomultiplier tube are both arranged opposite to the two-dimensional position sensitive detector, and the CCD camera and the photomultiplier tube are both connected to the computer.

[0014] The fused silica nozzle as described above is arranged on a three-dimensional adjustable platform, and the fused silica nozzle is connected to the sample cell through a high-pressure infusion pump.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] The present invention combines vacuum ultraviolet laser pulses with the OPA output laser (ultraviolet to infrared band) to achieve a time-resolved measurement function. It can not only use the vacuum ultraviolet laser as the pump light but also as the probe light. For the first time, the pump-probe method based on femtosecond vacuum ultraviolet laser pulses is further combined with a liquid beam photoelectron imaging device to achieve time-resolved liquid beam photoelectron imaging. Compared with the existing liquid beam imaging energy spectrum device, the present invention can not only obtain the kinetic energy information and angular distribution information of photoelectrons, thereby characterizing the structural changes of electrons and the interactions of molecules in real time, but also achieve a time-resolved measurement function. By introducing vacuum ultraviolet laser pulses into it, the problem that photons in the ultraviolet to infrared band cannot be directly single-photon ionized in conventional experiments is solved, enabling the ultrafast process of the entire photochemical reaction to be tracked in real time in a solution environment. It can detect molecular dynamics processes that cannot be detected in the ultraviolet to infrared band, such as photolysis and isomerization, which is very beneficial for realizing the ultrafast process of the entire photochemical reaction in real time in a solution environment. Brief Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of the device of the present invention;

[0018] 1a - femtosecond laser; 1b - first beam splitter (reflects 25%, transmits 75%); 1c - optical parametric amplifier (OPA); 1d - first mirror (250 - 400nm broadband high - reflection mirror); 1e - second mirror (250 - 400nm broadband high - reflection mirror); 1f - third mirror (250 - 400nm broadband high - reflection mirror); 1g - fourth mirror (250 - 400nm broadband high - reflection mirror); 1h - fifth mirror (250 - 400nm broadband high - reflection mirror); 1i - first concave mirror (250 - 400nm broadband high - reflection mirror); 1j - second concave mirror (250 - 400nm broadband high - reflection mirror); 1k - second beam splitter (reflects 50%, transmits 50%); 1l - sixth mirror (800nm high - reflection mirror); 1m - half - wave plate (800nm); 1n - seventh mirror (800nm high - reflection mirror); 1o - eighth mirror (800nm high - reflection mirror); 1p - first focusing lens (focal length is 1000mm); 1q - beam combiner; 1r - BBO frequency - doubling crystal (29.2°); 1s - ninth mirror (400nm high - reflection mirror); 1t - tenth mirror (400nm high - reflection mirror); 1u - eleventh mirror (400nm high - reflection mirror); 1v - twelfth mirror (400nm high - reflection mirror); 1w - thirteenth mirror (400nm high - reflection mirror); 1x - second focusing lens (focal length is 1000mm); 2a - krypton gas cylinder; 2b - filament - forming and four - wave mixing gas cell; 2c - first mechanical pump; 2d - second mechanical pump; 2e - first vacuum chamber; 2f - fourteenth mirror (160nm high - reflection mirror); 2g - fifteenth mirror (160nm high - reflection mirror); 3a - third mechanical pump; 3b - first molecular pump; 3c - second vacuum chamber; 3d - first cold trap; 3e - second molecular pump; 3f - fourth mechanical pump; 3g - polytetrafluoroethylene orifice plate; 3h - second cold trap; 4a - sample cell; 4b - high - pressure infusion pump; 4c - three - dimensional adjustable platform; 4d - fused - silica nozzle (aperture is 25 microns); 5a - repeller electrode; 5b - accelerating electrode; 5c - ground electrode; 5d - magnetic shielding cylinder; 5e - two - dimensional position - sensitive detector; 5f - CCD camera; 5g - photomultiplier tube (PMT); 5h - computer; 6 - first displacement platform; 7 - second displacement platform. Detailed implementation manners

[0019] For the convenience of those of ordinary skill in the art to understand and implement the present invention, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0020] As Figure 1As shown in the figure, a liquid beam photoelectron imaging device based on femtosecond vacuum ultraviolet laser pulses includes a femtosecond pump-probe optical path system, a four-wave mixing generation and transmission system, a vacuum maintenance system, a liquid beam sampling system, and a photoelectron collection and imaging detection system.

[0021] The femtosecond pump-probe optical path system includes a femtosecond laser 1a (outputting 800 nm femtosecond laser pulses), a first beam splitter 1b, an optical parametric amplifier (OPA) 1c, a first mirror 1d, a second mirror 1e, a third mirror 1f, a fourth mirror 1g, a fifth mirror 1h, a first concave mirror 1i, a second concave mirror 1j, a second beam splitter 1k, a sixth mirror 1l, a half-wave plate 1m, a seventh mirror 1n, an eighth mirror 1o, a first focusing lens 1p, a beam combining plate 1q, a BBO frequency doubling crystal 1r, a ninth mirror 1s, a tenth mirror 1t, an eleventh mirror 1u (400 nm high reflection mirror), a twelfth mirror 1v, a thirteenth mirror 1w, and a second focusing lens 1x.

[0022] The first mirror 1d, the second mirror 1e, the third mirror 1f, the fourth mirror 1g, the fifth mirror 1h, the first concave mirror 1i, and the second concave mirror 1j are broadband high reflection mirrors with a wavelength of 250 - 400 nm. Among them, the first mirror 1d and the second mirror 1e are installed on the second displacement platform and move with the movement of the second displacement platform. The first mirror 1d, the second mirror 1e, and the second displacement platform form the second optical path adjustment module.

[0023] The sixth mirror 1l, the seventh mirror 1n, and the eighth mirror 1o are high reflection mirrors with a wavelength of 800 nm.

[0024] The ninth mirror 1s, the tenth mirror 1t, the eleventh mirror 1u, the twelfth mirror 1v, and the thirteenth mirror 1w are high reflection mirrors with a wavelength of 400 nm. Among them, the eleventh mirror 1u and the twelfth mirror 1v are installed on the first displacement platform and move with the movement of the first displacement platform. The eleventh mirror 1u, the twelfth mirror 1v, and the first displacement platform form the first optical path adjustment module.

[0025] The first beam splitter 1b reflects 25% of the light energy and transmits 75% of the light energy. The second beam splitter 1k then reflects 50% and transmits 50% of the light that has passed through the first beam splitter 1b.

[0026] The BBO frequency doubling crystal 1r doubles the frequency of 800 nm to 400 nm.

[0027] The half-wave plate 1m adjusts the polarization of 800 nm from horizontal to vertical.

[0028] Optical parametric amplification (OPA) 1c uses non-linear optical means to convert 800 nm into a laser pulse output of 240 - 2600 nm.

[0029] The first focusing lens 1p and the second focusing lens 1x are both plano-convex lenses with a focal length of 1000 mm.

[0030] The femtosecond laser pulse with a wavelength of 800 nm passes through the first beam splitter 1b. 25% of the energy is reflected and 75% of the energy is transmitted, forming the first transmitted light and the first reflected light. The first reflected light first passes through the optical parametric amplification 1c, and then is reflected successively by the first mirror 1d, the second mirror 1e, the third mirror 1f, the fourth mirror 1g, and the fifth mirror 1h. After being reflected by the first concave mirror 1i and the second concave mirror 1j to adjust the incident angle, it finally acts on the transparent region of the liquid beam ejected from the fused quartz nozzle 4d. The first transmitted light first passes through the second beam splitter 1k. 50% of the energy is reflected and 50% of the energy is transmitted, forming the second transmitted light and the second reflected light. The second reflected light is first reflected by the sixth mirror 1l, then passes through the half-wave plate 1m, and then is reflected by the seventh mirror 1n and the eighth mirror 1o respectively and is focused by the first focusing lens 1p and then enters the beam combiner 1q. The second transmitted light first passes through the BBO frequency doubling crystal 1r. The 400 nm light obtained after frequency doubling passes through the ninth mirror 1s, the tenth mirror 1t, the eleventh mirror 1u, the twelfth mirror 1v, and the thirteenth mirror 1w successively, and then is focused by the second focusing lens 1x and enters the beam combiner 1q. Finally, the 800 nm light focused by the first focusing lens 1p and the 400 nm light focused by the second focusing lens 1x are combined by the beam combiner 1q to form the combined light.

[0031] The four-wave mixing generation and transmission system includes a high-purity krypton gas cylinder 2a, a filamentation and four-wave mixing gas cell 2b, a first mechanical pump 2c, a second mechanical pump 2d, a first vacuum chamber 2e, a fourteenth mirror 2f, and a fifteenth mirror 2g.

[0032] The filamentation and four-wave mixing gas cell 2b is connected to the first mechanical pump 2c and the krypton gas cylinder 2a. The first vacuum chamber 2e is connected to the second mechanical pump 2d. The fourteenth mirror 2f and the fifteenth mirror 2g are arranged in the first vacuum chamber 2e.

[0033] The fourteenth mirror 2f and the fifteenth mirror 2g are high-reflection mirrors with a wavelength of 160 nm.

[0034] First, use the first mechanical pump 2c and the second mechanical pump 2d to pump the vacuum degrees of the wire-forming and four-wave mixing gas cell 2b and the first vacuum chamber 2e below 5 Pa respectively. Then, open the valve of the high-purity krypton gas cylinder 2a, and inject 32 Torr of high-purity krypton gas into the wire-forming and four-wave mixing gas cell 2b. Next, make the combined beam of 400 and 800 nm light incident on the four-wave mixing gas cell 2b after being combined by the beam combiner 1q, and interact with the krypton gas therein. By adjusting the optical path, make the light with wavelengths of 400 and 800 nm in the combined beam coincide spatially, and adjust the first optical path adjustment module to make the optical paths of the light with wavelengths of 400 and 800 nm in the combined beam consistent. At this time, light with a wavelength of 160 nm will be generated. The light with a wavelength of 160 nm then enters the first vacuum chamber 2e, and finally, after the fourteenth mirror 2f and the fifteenth mirror 2g adjust the angles, it enters the second vacuum chamber (3c) through the vacuum interface and acts on the transparent area of the liquid beam ejected from the fused silica nozzle (4d).

[0035] The vacuum maintenance system includes a third mechanical pump 3a, a first molecular pump 3b, a second vacuum chamber 3c, a first cold trap 3d, a second molecular pump 3e, a fourth mechanical pump 3f, an orifice plate 3g (polytetrafluoroethylene orifice plate), and a second cold trap 3h.

[0036] An orifice plate 3g is arranged in the second vacuum chamber 3c. A fused silica nozzle 4d and a first cold trap 3d are arranged on the top side wall on the left side of the orifice plate 3g in the second vacuum chamber 3c. A first molecular pump 3b is arranged at the left end of the second vacuum chamber 3c, and the first molecular pump 3b is connected to the third mechanical pump 3a.

[0037] An extraction electrode 5a, an acceleration electrode 5b, and a ground electrode 5c are arranged in sequence from left to right below the fused silica nozzle 4d in the second vacuum chamber 3c. A second cold trap 3h is arranged on the side wall below the fused silica nozzle 4d in the second vacuum chamber 3c.

[0038] A magnetic shielding cylinder 5d is arranged on the right side of the orifice plate 3g in the second vacuum chamber 3c. A second molecular pump 3e is also arranged on the bottom side wall on the right side of the orifice plate 3g in the second vacuum chamber 3c, and the second molecular pump 3e is connected to the fourth mechanical pump 3f.

[0039] A two-dimensional position-sensitive detector 5e is arranged at the right end of the second vacuum chamber 3c. The CCD camera 5f and the photomultiplier tube 5g are both arranged opposite to the two-dimensional position-sensitive detector 5e, and the CCD camera 5f and the photomultiplier tube 5g are both connected to the computer 5h.

[0040] The fused silica nozzle 4d is arranged on a three-dimensional adjustable platform 4c, and the fused silica nozzle 4d is connected to the sample cell 4a through a high-pressure infusion pump 4b.

[0041] The first molecular pump 3b, the first cold trap 3d, the second molecular pump 3e, and the second cold trap 3h are respectively connected to the second vacuum chamber 3c through their respective flanges. The third mechanical pump 3a is connected to the first molecular pump 3b through a bellows. Similarly, the fourth mechanical pump 3f is also connected to the second molecular pump 3e through a bellows. When there is no sample injection, through the combination of the third mechanical pump 3a and the first molecular pump 3b, the vacuum degree of the left side cavity of the orifice plate 3g (polytetrafluoroethylene orifice plate) can be pumped to 10 -6 order of magnitude. Similarly, through the combination of the second molecular pump 3e and the fourth mechanical pump 3f, the vacuum degree of the right side cavity of the orifice plate 3g (polytetrafluoroethylene orifice plate) can be pumped to 10 -6 order of magnitude. When injecting liquid, liquid nitrogen is filled into the first cold trap 3d and the second cold trap 3h. And due to the differential pumping system formed by the orifice plate 3g (polytetrafluoroethylene orifice plate), the vacuum degree of the left side chamber of the orifice plate 3g (polytetrafluoroethylene orifice plate) can be maintained at 10 -2 -10 -3 order of magnitude, and the vacuum degree of the right side chamber can be maintained at 10 -4 -10 -5 order of magnitude.

[0042] The liquid beam injection system includes a sample cell 4a, a high-pressure liquid delivery pump 4b, a three-dimensional adjustable platform 4c, and a fused silica nozzle 4d. Through the high-pressure liquid delivery pump 4b, the liquid in the sample cell 4a can be pumped out from the fused silica nozzle 4d at a pressure of MPa, and a beam with a stable flow rate is formed within a range of 2 - 3 mm below the outlet of the fused silica nozzle 4d, which is defined as the liquid beam transparent region. The three-dimensional adjustable platform 4c has three adjustable directions of X, Y, and Z, and can precisely adjust the position of the fused silica nozzle 4d, thereby adjusting the region where the liquid beam transparent region interacts with the laser.

[0043] The optoelectronic collection and imaging detection system includes a repelling electrode 5a, an accelerating electrode 5b, a ground electrode 5c, a magnetic shielding cylinder 5d, a two-dimensional position-sensitive detector 5e, a CCD camera 5f, a photomultiplier tube (PMT) 5g, and a computer 5h. A voltage is applied to the repelling electrode 5a and the accelerating electrode 5b, and the voltage ratio is 1:0.67. The voltage on the ground electrode 5c is 0V. The magnetic shielding cylinder 5d is used to shield the external magnetic field to eliminate the influence of the external magnetic field on the particle flight trajectory. When the laser pulse interacts with the transparent region of the liquid beam, the liquid molecules are ionized, and electrons fly out from the gas-liquid surface. Under the combined action of the repelling electrode 5a, the accelerating electrode 5b, and the ground electrode 5c, they are accelerated and focused to fly towards the two-dimensional position-sensitive detector 5e. The two-dimensional position-sensitive detector 5e includes a microchannel plate MCP and a phosphor screen PS. When electrons reach the two-dimensional position-sensitive detector 5e, first, the electron signal is amplified by more than one million times through the microchannel plate MCP, then the electrical signal is converted into an optical signal through the phosphor screen PS, and finally, they are received by the CCD camera 5f and the photomultiplier tube (PMT) 5g respectively. The received signals can be recorded by the computer 5h to obtain the kinetic energy distribution and angular distribution of the liquid-phase photoelectrons. Also, the voltages of the repelling electrode 5a and the accelerating electrode 5b can be changed to positive voltages to collect ion signals, so that the time-of-flight mass spectrum of different charge-to-mass ratios in the liquid can be obtained.

[0044] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A liquid beam photoelectron imaging device based on femtosecond vacuum ultraviolet laser pulses, comprising a femtosecond laser (1a). It is characterized in that the femtosecond laser (1a) emits femtosecond laser, which is split into a first reflected light and a first transmitted light by a first beam splitter (1b). The first transmitted light is split into a second reflected light and a second transmitted light by a second beam splitter (1k). The second transmitted light sequentially passes through a BBO frequency doubling crystal (1r), a first optical path adjustment module, and a second focusing lens (1x) and then is incident on a beam combiner (1q). The second reflected light sequentially passes through a half-wave plate (1m) and a first focusing lens (1p) and then is incident on the beam combiner (1q). The combined light emitted by the beam combiner (1q) is incident on a filament formation and four-wave mixing gas cell (2b). The light emitted by the four-wave mixing gas cell (2b) enters a first vacuum chamber (2e) through a vacuum interface. After the incident angle is adjusted by a mirror in the first vacuum chamber (2e), it then enters a second vacuum chamber (3c) through the vacuum interface and acts on the transparent region of the liquid beam ejected from a fused silica nozzle (4d). The first optical path adjustment module is adjusted so that the second transmitted light passing through the BBO frequency doubling crystal (1r), the first optical path adjustment module, and the second focusing lens (1x) and the second reflected light passing through the half-wave plate (1m) and the first focusing lens (1p) have the same optical path. The first reflected light sequentially passes through an optical parametric amplifier (1c) and a second optical path adjustment module, and then is reflected and the incident angle is adjusted by a first concave mirror (1i) and a second concave mirror (1j) in sequence, and then enters the second vacuum chamber (3c) and acts on the transparent region of the liquid beam ejected from the fused silica nozzle (4d). The filament formation and four-wave mixing gas cell (2b) is connected to a first mechanical pump (2c), the first vacuum chamber (2e) is connected to a second mechanical pump (2d), and the filament formation and four-wave mixing gas cell (2b) is also connected to a krypton gas cylinder (2a). A perforated plate (3g) is provided in the second vacuum chamber (3c). A fused silica nozzle (4d) and a first cold trap (3d) are provided on the top side wall on the left side of the perforated plate (3g) in the second vacuum chamber (3c). A first molecular pump (3b) is provided at the left end of the second vacuum chamber (3c), and the first molecular pump (3b) is connected to a third mechanical pump (3a). A repelling electrode (5a), an accelerating electrode (5b), and a ground electrode (5c) are sequentially provided from left to right below the fused silica nozzle (4d) in the second vacuum chamber (3c). A second cold trap (3h) is provided on the side wall below the fused silica nozzle (4d) in the second vacuum chamber (3c). A magnetic shielding cylinder (5d) is provided on the right side of the perforated plate (3g) in the second vacuum chamber (3c). A second molecular pump (3e) is also provided on the bottom side wall on the right side of the perforated plate (3g) in the second vacuum chamber (3c), and the second molecular pump (3e) is connected to a fourth mechanical pump (3f). A two-dimensional position-sensitive detector (5e) is provided at the right end of the second vacuum chamber (3c). The CCD camera (5f) and the photomultiplier tube (5g) are both arranged opposite to the two-dimensional position-sensitive detector (5e). The CCD camera (5f) and the photomultiplier tube (5g) are both connected to the computer (5h). The fused silica nozzle (4d) is arranged on a three-dimensional adjustable platform (4c). The fused silica nozzle (4d) is connected to the sample cell (4a) through a high-pressure infusion pump (4b).

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