Isotope abundance and ratio detection device and method based on molecular emission spectrum

Abstract

The invention relates to the technical field of isotope detection, in particular to a molecular emission spectrum-based isotope abundance and ratio detection device and a molecular emission spectrum-based isotope abundance and ratio detection method. The device comprises a computer, and a long pulse laser unit, a light path transmission unit, an LED illumination focusing unit, a three-dimensional displacement table and a spectrograph which are connected with the computer. Existing viewpoints consider that long-pulse laser is not beneficial to microcell excitation and high-resolution spectrum acquisition due to wide pulse width, so that the long-pulse laser is less applied to isotope fine spectral line difference identification. According to the invention, the signal intensity is enhanced in a breakthrough manner through a molecular emission cascade mechanism, the possibility of micro-area high-resolution isotope molecule detection is realized, and rapid, accurate and real-time in-situ detection of isotope abundance and ratio in a sample is realized by generating plasma and inducing a molecular emission spectrum through in-situ laser ablation. The device has the advantages of few optical elements, simple structure, convenient optical path adjustment, and facilitation of miniaturization and on-site application and popularization.

Description

Technical Field

[0001] This invention relates to the field of isotope detection technology, specifically to an isotope abundance and ratio detection device and method based on molecular emission spectroscopy, which can realize in-situ, rapid, and automated detection of isotope abundance and ratio. Background Technology

[0002] Isotope abundance and ratio detection technologies have significant applications in various fields, including nuclear energy development, geological exploration, environmental monitoring, and life sciences. The subtle differences in physical and chemical properties among different isotopes offer unique advantages in tracer analysis, age determination, and monitoring of nuclear reaction processes. For example, in the nuclear fuel cycle, accurately determining the isotopic abundance of radioactive elements such as uranium or plutonium is crucial for ensuring reactor safety and efficiency; in geological sample analysis, the ratios of different lead or strontium isotopes can be used to determine the age and formation environment of minerals; and in medical diagnostics and pharmacokinetics studies, changes in the abundance of stable isotope markers can be used to monitor metabolic pathways and drug absorption. Therefore, developing an analytical technique for rapidly, accurately, and non-destructively detecting the isotopic abundance and ratio in materials is of great scientific and practical value for improving material tracking capabilities, strengthening process control, ensuring system safety, and expanding the application areas of isotopes.

[0003] In current isotope detection, atomic absorption spectroscopy is the more commonly used technique, primarily used to distinguish energy level structure changes caused by differences in nuclear mass among isotopes. Atomic absorption spectroscopy analyzes the line spectra generated by electronic energy level transitions in gaseous atoms or ions, accurately capturing the absorption peak shifts caused by differences in nuclear mass. For example, the absorption peak shift between uranium-235 and uranium-238 is approximately 0.004 nm. This method offers high resolution and sensitivity, making it suitable for detecting light element isotopes such as carbon-13 and carbon-12. However, this method also has significant limitations, including extremely narrow spectral lines, weak signal background, significant susceptibility to Stokes broadening, significant matrix interference, and poor measurement repeatability. In particular, since the absorption linewidth is typically greater than the spectral line shift between isotopes, detectors with picometer (pm) level ultra-high resolution are required, which presents a high technical hurdle and cost constraint in experimental implementation.

[0004] The current mainstream view holds that molecular emission spectroscopy is not used as a technical means to detect isotope abundance and ratio because of its blurred band structure, severe energy level overlap, difficulty in distinguishing isotope shifts caused by differences in nuclear mass, low signal-to-noise ratio and limited spectral resolution in complex backgrounds. Instead, high-resolution analysis methods such as atomic absorption spectroscopy or mass spectrometry are more commonly used.

[0005] However, mass spectrometry relies on high-precision mass analysis instruments to obtain abundance information by separating and detecting isotopic ions in a sample. Although mass spectrometry offers high sensitivity and resolution, it still faces many limitations in practical applications. Firstly, mass spectrometry analysis typically requires complex sample pretreatment steps, making in-situ detection impossible and failing to meet the demands of industrial production for rapid, non-destructive measurements. Secondly, traditional mass spectrometry processes are time-consuming, lacking real-time monitoring and timely feedback on dynamic processes. Furthermore, in the analysis of samples involving radioactive materials such as uranium, mass spectrometry often requires manual sampling, which is not only inefficient but also poses a high risk of radiation exposure, causing irreversible harm to the operator's health.

[0006] Therefore, developing a device and method that can achieve in-situ, rapid, and automated detection of isotope ratios and abundances has significant application value for improving industrial production efficiency and safety levels.

[0007] Furthermore, traditional laser ablation atomic absorption spectroscopy faces significant technical bottlenecks in hydrogen / deuterium isotope analysis. On one hand, Stark broadening is extremely pronounced in laser-induced plumes formed under atmospheric pressure. On the other hand, laser-induced plasma (LIP) of water samples typically exhibits extremely high electron density, significantly exacerbating Stark broadening. In particular, H… a and D a The Stark broadening factor of the emission spectral lines is already at its highest level, leading to further broadening of the spectral lines and making spectral analysis even more difficult. Although delaying the signal acquisition time can suppress broadening to some extent, the rapid decay of emission intensity over time significantly reduces the detection signal-to-noise ratio. Therefore, traditional laser ablation atomic absorption spectroscopy is insufficient to meet the requirements for high-precision D / H isotope abundance measurement in water. Furthermore, the isotope shifts in the hydrogen atomic absorption lines are extremely small, and H… a With D a The shift is only about 18 pm, which is close to the resolution limit of most conventional spectrometers, making it a challenging task to accurately distinguish H and D abundance.

[0008] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0009] Although current mainstream understanding holds that molecular emission spectroscopy is not a primary technique for detecting isotopic abundance and ratio due to its blurred band structure, severe energy level overlap, difficulty in distinguishing isotopic shifts caused by differences in nuclear mass, low signal-to-noise ratio, and limited spectral resolution in complex backgrounds, with atomic absorption spectroscopy or mass spectrometry requiring extremely high resolution detection being more commonly used, this invention is the first to propose applying long-pulse laser-induced molecular emission spectroscopy to the field of quantitative isotope detection. This breakthrough overcomes the traditional perception that "molecular spectral signals are weak, background interference is strong, and high-resolution extraction is difficult," and constructs an integrated excitation-acquisition detection platform with highly collaborative and integrated capabilities.

[0010] This invention significantly enhances spectral line intensity through a cascaded amplification mechanism of molecular emission, supplemented by a high-pressure inert gas environment to extend plasma lifetime and stabilize the emission window. It combines a delayed-gated acquisition strategy with an AsLS+SNIP composite algorithm to achieve background suppression and baseline correction, enabling clear identification of weak isotope shift signals in complex environments. Particularly for heteronuclear diatomic molecules such as OH / OD and CN, whose vibrational-rotational energy level structures are highly sensitive to reduced mass, with molecular spectral head shifts reaching more than 10 times that of atomic spectral lines, this invention achieves isotope molecular head separation with an accuracy of 0.015 nm using a spectrometer system. This allows for in-situ automated detection of isotope ratios such as D / H and 13C / 12C in water or organic samples under non-derivative processing conditions.

[0011] Therefore, this invention not only challenges the traditional view that "molecular spectroscopy cannot be used for high-precision isotope analysis," but also achieves a synergistic breakthrough in signal enhancement, background reduction, and significantly improved analytical accuracy through multiple innovations in light source control, signal acquisition, spectral processing, and system structure, fully demonstrating the originality and practical value of this technical solution.

[0012] In summary, to address the shortcomings of existing technologies, this invention overcomes technical biases and provides a high-precision detection device and method for isotope abundance and ratio based on long-pulse laser ablation of molecular emission spectra. Compared to the short-pulse lasers commonly used in existing technologies, this invention employs a long-pulse laser, which is less common in this field. By ablating molecular emission spectra with a long-pulse laser, in-situ, rapid, and automated detection of isotope abundance and ratio is achieved. Compared to existing devices, this invention offers lower cost, stronger repeatability, higher signal-to-noise ratio, and superior data processing capabilities, possessing the potential for widespread application in practical environmental monitoring and online detection.

[0013] The technical solution of this invention is as follows:

[0014] An isotope abundance and ratio detection device based on molecular emission spectroscopy includes a single long-pulse laser unit for emitting laser pulses with a pulse width ≥100ns, a frequency of 1~10Hz, and an energy of 0~120mJ to excite the sample to be tested to generate plasma.

[0015] The optical path transmission unit receives long-pulse laser light and, through a group of mirrors, a first beam splitter, a dichroic mirror, and a microscope objective, reflects and focuses the laser light onto the surface of the sample to be tested. Simultaneously, it introduces plasma-emitted light into the detection optical path. The LED illumination and focusing unit, including LED white light illumination, a reflector, and a monitoring camera, provides auxiliary white light illumination under the microscope objective and allows real-time observation of the focal plane.

[0016] A three-dimensional displacement stage, electrically connected to a computer, is used to locate detection points in the X / Y plane and achieve automatic or manual focusing in the Z direction.

[0017] The sealed sample chamber unit includes a sealed gas chamber body, an optical window, a gas inlet and outlet, and a pressure control system, which is used to maintain a high-pressure inert gas environment in the sample area to be tested.

[0018] The spectrometer, including collimating lens, focusing lens, planar grating, grating driver, wavelength display meter, ICCD (an enhanced charge-coupled device camera) and EMCCD (electron multiplier CCD), supports adjustable parameters such as external triggering, delay, gate width, and gain, and is used for molecular spectroscopy and detection.

[0019] The computer, connected to the long-pulse laser unit, optical path transmission unit, LED illumination focusing unit, three-dimensional displacement stage, and spectrometer, is used to control the emission timing and parameters of the long-pulse laser; drive the LED illumination and three-dimensional displacement stage to achieve focusing and sample point switching; adjust the center wavelength and ICCD gating parameters of the spectrometer and trigger spectral acquisition; perform baseline correction, background removal, and multi-peak fitting on the acquired molecular spectra; and calculate the isotopic abundance and ratio of the sample to be tested.

[0020] Furthermore, the long-pulse laser unit includes:

[0021] The pump cavity is used to provide pump energy for the laser medium and achieve population inversion.

[0022] An acousto-optic Q-switching cavity includes a transducer, power supply, acousto-optic medium, sound-absorbing material, and cooling system. It achieves instantaneous laser release through Q-switching via acousto-optic diffraction.

[0023] The laser controller and its accompanying software are used to adjust the pump source drive, Q-switch triggering, and laser output parameters, and to communicate with a computer.

[0024] Furthermore, the reflector group includes 6 reflectors. The long-pulse laser unit emits laser light, which passes through a lifting optical path composed of two reflectors to reach two reflectors constrained by a cage structure, which remains horizontal. The light then passes through the lifting optical path composed of two reflectors to be incident on the beam splitter. One beam of light illuminates the PIN tube, and the other beam of light passes through a dichroic mirror and is focused onto the surface of the sample to be tested by the microscope objective.

[0025] Furthermore, the first beam splitter is placed behind the last reflector. The first beam splitter uses the reflection and transmission properties of the optical thin film to split the incident light into two parts. When the light beam passes through the first beam splitter, part of the light is reflected and the other part of the light passes through the first beam splitter. The transmitted light illuminates the PIN tube, and the reflected light is incident on the dichroic mirror.

[0026] The dichroic mirror is positioned below the first beam splitter, and it can separate the excitation laser from the plasma emission light.

[0027] The reflector is detachably mounted below the dichroic mirror. The reflector is used to reflect the light emitted by the LED light source to achieve imaging and focusing. When not in focus, the operator can remove the reflector, and the laser passing through the dichroic mirror can directly reach the microscope objective. The long-pulse laser reaching the microscope objective will be focused to excite the sample to generate plasma. After the reflector is installed, it can be used in conjunction with the LED illumination focusing unit to produce imaging effect. Moreover, the molecular signal light generated by the plasma can be collected and coupled into the optical fiber for spectroscopic detection.

[0028] Furthermore, the spectrometer includes a PIN diode trigger circuit, wherein the PIN diode receives the laser pulse transmitted by the first beam splitter and outputs a trigger signal to realize ICCD external trigger acquisition, with the delay set to 2-50μs and the gate width set to 20-150μs.

[0029] Furthermore, the pressure control system of the sealed sample chamber unit includes a pressure sensor, a regulating valve, and a safety alarm device, used to monitor and maintain the inert gas pressure within a preset range of 101 kPa ± 1 kPa in real time.

[0030] Furthermore, the computer can call molecular spectroscopy fitting software, load the rotation-vibration constants and spectral line list, automatically complete multi-peak fitting, and output isotope abundance and ratio.

[0031] A method for detecting isotope abundance and ratio based on molecular emission spectroscopy, comprising: an excitation method and a detection method;

[0032] The excitation method includes:

[0033] The sample to be tested is placed in a sealed gas chamber filled with high-pressure inert gas;

[0034] The moving displacement stage is used for focusing;

[0035] A long-pulse laser is turned on and focused onto the sample surface through the optical path to excite the plasma. The plasma emits molecular spectra after a few μs.

[0036] The detection method includes:

[0037] The molecular spectral signal emitted by the plasma is reflected by a dichroic mirror and enters the optical fiber;

[0038] The optical fiber couples the signal light into the spectrometer, and the spectrometer starts to work and collect the signal spectrum when triggered by the PIN diode.

[0039] The collected data underwent baseline correction and background removal;

[0040] The processed data is then fitted with molecular spectra to analyze the isotopic abundance and ratio of the sample.

[0041] Specifically, it includes the following steps:

[0042] (1) Sample placement: The isotope-enriched sample particles are placed in the sealed sample chamber unit, and the inert pressure is adjusted to 101kPa±1kPa.

[0043] (2) Microscopic focusing: Turn on the LED white light illumination and drive the three-dimensional displacement stage to make the sample surface coincide with the focal plane of the microscope objective.

[0044] (3) Plasma excitation: The long pulse laser unit is triggered according to the set frequency and energy, and the laser is focused onto the sample surface through the optical path transmission unit to generate plasma;

[0045] (4) Spectral acquisition: The plasma begins to emit molecular spectra 2-15 μs after excitation. The signal is reflected by a dichroic mirror and coupled into an optical fiber. Under the triggering of the PIN tube, the wavelength in the spectrometer and the ICCD are adjusted to acquire the spectrum at a gate width of 30-150 μs.

[0046] (5) Data Processing: The original spectrum is processed using the asymmetric least squares (AsLS) and statistically sensitive nonlinear iterative peak (SNIP) algorithms for baseline correction and background removal. Then, the shift of the isotopic molecular head is analyzed through multi-peak fitting. Specifically, the molecular emission spectrum in this invention includes the molecular characteristic peaks, atomic peaks, continuous background radiation (bremsstrahlung or recombination radiation from the plasma), and instrument noise. Baseline drift (caused by plasma temperature fluctuations, unstable instrument response, etc.) can mask weak molecular peaks, affecting the accurate identification of peak positions and intensities. The core idea of ​​the AsLS algorithm is to dynamically adjust the smoothing degree through least squares fitting combined with adaptive regularization—using strong smoothing in the baseline region (no peaks or weak peaks) to fit the baseline; and using weak smoothing in the characteristic peak region (where the signal changes abruptly) to preserve peak details (such as peak position, full width at half maximum, and intensity). The core function of the AsLS algorithm is to adaptively fit the baseline and remove drift, preserving the original shape of the molecular characteristic peaks. After baseline removal, structured background (such as continuous radiation from matrix elements and broad peak interference from molecular clusters) still exists. This background may overlap with the target molecule peaks, leading to peak identification and integration errors. The core idea of ​​the SNIP algorithm is that it repeatedly calculates the local minimum of the spectrum within different windows, treating signals above the local minimum as "part of the peak" and signals below or equal to the local minimum as "background," ultimately retaining the true peaks and subtracting the smoothed background. The SNIP algorithm is an efficient background subtraction method, especially suitable for spectral processing against complex backgrounds.

[0047] (6) Isotope calculation: Call the molecular spectroscopy fitting software (Pgopher molecular spectroscopy software), load the list of molecular constants and spectral lines, automatically fit and output the isotope abundance and ratio of the sample to be tested.

[0048] Furthermore, the AsLS and SNIP algorithms can be used individually or in combination, and residual baselines can be further removed through continuous wavelet transform and interpolation.

[0049] Furthermore, the center wavelength of the spectrometer is scanned by a stepper motor and a sine arm driving the grating within the range of 190–800 nm, with a wavelength repeatability of ±0.005 nm.

[0050] The beneficial effects achieved by this invention are as follows:

[0051] 1. Existing viewpoints suggest that long-pulse lasers, due to their wide pulse width, are unfavorable for micro-area excitation and high-resolution spectral acquisition, thus limiting their application in identifying subtle spectral differences in isotopes. This invention, however, innovatively enhances signal intensity through a molecular emission cascade mechanism, enabling high-resolution micro-area isotope molecular detection. By generating plasma through in-situ laser ablation and inducing molecular emission spectra, rapid, accurate, and real-time in-situ detection of isotope abundance and ratios in samples is achieved. This detection scheme combines the deep excitation effect of long-pulse lasers on local sample regions with the characteristic emission behavior of molecular spectra in the later stages of the reaction, significantly enhancing the intensity and stability of the molecular spectral signal. This provides a feasible and widely applicable technical path for efficient isotope detection in industrial applications.

[0052] 2. This invention achieves isotope detection through molecular emission spectroscopy, utilizing the large displacement and high-intensity characteristic spectral lines resulting from intermolecular vibrational and rotational transitions. Compared to atomic absorption spectroscopy, the signal is enhanced by more than 30 times, and the isotope shift is significantly increased to more than ten times that of atomic spectroscopy. Detection targets such as OH and OD groups are naturally formed during laser ablation, and their spectral lines directly reflect the D / H ratio in the sample, eliminating the need for any derivatization pretreatment steps, significantly simplifying the experimental procedure and improving data reliability.

[0053] 3. This invention employs a single long-pulse laser to simultaneously perform excitation and detection, ensuring high system coordination and timing consistency, thereby improving experimental reproducibility and integration. Its pulse width is highly matched to the timescale of molecular bond breaking and reaction formation, which is beneficial for the continuous generation of excited-state molecules and the formation of an emission cascade mechanism. Furthermore, the equipment is low-cost, highly versatile, and applicable to the vast majority of experimental platforms.

[0054] 4. In this invention, excitation and detection occur simultaneously from the same source, significantly simplifying the optical path system, reducing sources of error, ensuring experimental repeatability and operational efficiency, and improving data reliability. The entire device has a simple structure, requires a significantly reduced number of optical components, and is easy to adjust, which is conducive to equipment miniaturization and field application.

[0055] 5. The timing control strategy in this invention is based on real-time laser emission signal feedback. Through the beam splitting-PIN detection-electrical signal synchronization-spectrometer delayed start mechanism, it automatically completes the precise alignment of the acquisition time window with the plasma emission process, which greatly improves data accuracy and repeatability.

[0056] 6. In this invention, the microscope objective not only undertakes the task of focusing, but also integrates multiple functions such as image imaging, sample micro-area capture, autofocus and signal enhancement. Combined with LED and CMOS camera, it realizes real-time control, image feedback and precise data acquisition during the experiment.

[0057] 7. The three-dimensional displacement platform of this invention enables active focusing control in the vertical direction. Combined with a laser displacement feedback system, it can automatically adjust the sample height, maintaining consistent focus throughout the surface scanning process and avoiding signal deviation. The microscope objective possesses a high numerical aperture and achromatic properties, enabling both high-precision laser focusing and complex operations such as sample image imaging and micro-area spectral acquisition. It is a core optical component for achieving spatially resolved precision spectral measurements. The triple-collaboration system of microscope objective + LED + camera allows for automatic imaging and focusing adjustment, improving signal strength, significantly shortening focusing time, and increasing experimental efficiency.

[0058] 8. This invention supports automatic export and batch processing of spectral data, allowing users to freely perform operations such as baseline fitting, background subtraction, and spectral line enhancement according to specific analytical needs, greatly improving data accuracy and research depth. The embedded timing control mechanism avoids human error settings and improves system consistency. During laser emission, the PIN detector is triggered via the beam splitting path, and this signal synchronously starts the spectrometer's delayed acquisition, ensuring precise alignment of data acquisition during the plasma emission phase, effectively enhancing the signal-to-noise ratio and suppressing background interference.

[0059] 9. The entire detection process of this invention, from sample placement to result output, takes only 3 minutes, significantly better than the 10+ minutes required by existing devices. In terms of accuracy and performance, this invention extends the plasma lifetime to 50-100 μs by filling with 101 kPa argon or helium gas, increasing molecular emission intensity by 3 times and achieving a signal-to-noise ratio of 200:1, far exceeding the 80:1 of other commonly used measurement systems. The long-pulse laser with a pulse width ≥100 ns provides sufficient energy to ablate the sample while avoiding plasma transient instabilities caused by femtosecond lasers. A 2-5 μs delay in molecular spectrum acquisition effectively avoids atomic line interference; combined with a spectrometer, the isotope abundance detection limit is as low as 0.1%, better than the 0.5-1% of existing commonly used measurement systems. The repeatability error of this invention is less than 2%, meeting the high-precision requirements of industrial applications.

[0060] In summary, this invention is significantly superior to existing devices in terms of system integration, experimental reliability, spectral signal quality, and operational automation. It also boasts lower cost, stronger repeatability, higher signal-to-noise ratio, and better data processing capabilities, and has the potential to be promoted for practical environmental monitoring and online detection applications. Attached Figure Description

[0061] Figure 1 This is a schematic diagram illustrating the difference between the long-pulse laser and the short-pulse laser of the present invention.

[0062] Figure 2 This is a schematic diagram of the overall structure of the device of the present invention.

[0063] Figure 3 This is the present invention. Figure 2 A schematic diagram of the structure of the central reflecting mirror assembly.

[0064] Figure 4 This is a schematic diagram of the structure of the three-dimensional displacement stage in this invention.

[0065] Figure 5 This is a schematic diagram of the sealed sample chamber unit in this invention.

[0066] Figure 6 yes Figure 2 A schematic diagram of the structure of a medium spectrometer.

[0067] Figure 7 This is a timing control diagram of the device of the present invention.

[0068] Figure 8 This is a flowchart of the method of the present invention.

[0069] Figure 9 This is a graph showing the results of an experiment on the molecular spectra of H and D isotopes.

[0070] Figure 10 This is a graph showing the fitting results of the absolute abundance of H / D isotope molecular spectra with the ratio of molecular spectra.

[0071] Figure 11 It is d 3 Πg→a 3 Graph of molecular spectra of Πμ(1-0)CC isotopes.

[0072] Figure 12 This is a spectral result of OH molecules under an inert gas environment.

[0073] Figure 13 This is a spectral result of an OH molecule experiment in air.

[0074] Figure 14 It is B 2 Σ+→X 2 Σ+(0-1)CN isotope molecular spectra experimental results.

[0075] In the figure, 1. Long-pulse laser; 2. Mirror group; 21. Mirror I; 22. Mirror II; 23. Mirror III; 24. Mirror IV; 25. Mirror V; 26. Mirror VI; 3. First beam splitter; 4. Dichroic mirror; 5. Microscope objective; 6. LED white light illumination; 7. Reflector; 8. Camera; 9. Three-dimensional displacement stage; 91. X-axis drive unit; 92. Y-axis drive unit; 93. Z-axis drive unit; 94. Sample stage; 10. Spectrometer; 101. Planar grating; 102. Grating driver; 103. Focusing lens; 104. Wavelength display; 105. ICCD; 106. Spectroscopic mirror; 107. EMCCD; 108. Collimating lens; 109. Slit; 11. PIN tube; 12. Sealed sample chamber unit; 121. Sealed gas chamber body; 122. Optical window; 123. Gas inlet and outlet; 13. Sample to be tested; 14. Inert gas container; 15. Computer. Detailed Implementation

[0076] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0077] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate preferred embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0078] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0079] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0080] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0081] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0082] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0083] Example 1: Device and method for detecting isotopic abundance and ratio based on molecular emission spectroscopy

[0084] like Figures 2-8As shown, this invention provides an isotope abundance and ratio detection device and method based on molecular emission spectroscopy. The working principle is based on long-pulse laser ablation of the sample to generate plasma emission molecular spectra. Combined with a spectrometer 10 with a resolution of 0.015 nm, the isotope shifts at the molecular emission head can be accurately resolved. The device achieves simultaneous excitation and detection of molecular spectra through the cooperation of multiple units, including: a long-pulse laser 1, an optical path transmission unit, an LED illumination focusing unit, a three-dimensional displacement stage 9, a sealed sample chamber unit 12, a spectrometer 10, and a computer 15.

[0085] Long-pulse laser 1 is used to emit a long-pulse, low-repetition-rate 1064nm laser. It is first pumped from the side of a YAG crystal using pump light emitted from a semiconductor laser diode (LD). Then, acousto-optic Q-switching is performed. Initially, the incident laser beam diffracts in the acousto-optic crystal, preventing oscillation. Under pump light excitation, a large number of inverted particles accumulate in the laser medium. Once a certain level is reached, the accumulated inverted particles are converted into laser energy through stimulated emission within a very short time, forming a high-intensity, short-pulse output. As the output laser pulse is released, the inverted particle number rapidly decreases, and the laser pulse gradually decays until it stops oscillating, awaiting the next pump and Q-switching cycle. The adjustable laser frequency is 1-10Hz, and the laser energy is 0-120mJ.

[0086] The optical transmission unit is used to transmit long-pulse laser. The long pulse is incident on the first beam splitter 3 through the reflector group. The reflected long-pulse laser passes through the dichroic mirror 4. The transmitted laser is focused onto the surface of the sample 13 under test through the microscope objective 5.

[0087] The LED lighting focusing unit and the three-dimensional displacement stage 9 are used. The LED light source emits LED light, which passes through the reflector 7 and is reflected onto the surface of the sample 13 to be tested. The projected light source reaches the camera 8 to observe the focusing situation. The focusing process is achieved by moving the displacement stage to achieve laser focusing.

[0088] The spectrometer 10, driven by a motor, rotates a grating to the required detection center wavelength depending on the isotope being detected. The operator can determine the center wavelength after grating rotation using a wavelength display 104 to ensure it matches the required wavelength for the experiment. The spectrometer is equipped with Andor's original ICCD105 and EMCCD107. The operator selects between the ICCD105 and EMCCD107 by rotating the internal mirrors of the spectrometer, choosing the ICCD105 with its ultrafast time resolution for isotope detection. Long-pulse light transmitted through the first beam splitter 3 reaches the PIN tube 11, which is connected to the spectrometer 10. When a laser is present, the PIN tube 11 triggers the spectrometer 10 to acquire molecular spectra.

[0089] The sealed sample chamber unit 12 is used to place the sample to be tested 13 and to fill it with high-pressure inert gas to create an inert gas environment.

[0090] Computer 15 is connected to long-pulse laser 1, spectrometer 10, and displacement stage. It is used to adjust the laser parameters, realize manual and automatic sample focusing, and set the acquisition parameters of spectrometer 10.

[0091] This embodiment combines a long-pulse, low-repetition-rate laser with a high-pressure inert gas sample environment and a high-resolution spectrometer 10, achieving close collaboration between molecular spectroscopy excitation and detection analysis. The long-pulse laser can fully ablate the sample, improving the signal of the molecular spectrum. The high-pressure inert gas environment enhances the plasma lifetime and temperature, reduces air interference, and improves the stability of the molecular signal. The spectrometer 10, with a resolution of 0.015 nm, can accurately resolve the isotopic shifts of the molecular emission band head.

[0092] Specifically, an isotope abundance and ratio detection device based on molecular emission spectroscopy includes:

[0093] A single long-pulse laser 1 is used to emit laser pulses with a pulse width of ≥100ns, a frequency of 1~10HZ, and an energy of 0~120mJ to excite the sample 13 to generate plasma.

[0094] The long-pulse laser 1 includes a pump region, a Q-switching region, a controller region, and a software region. The pump region provides pump energy to pump ground-state particles in the laser medium to upper energy levels, forming population inversion. Stimulated emission amplifies the light and initially generates laser light. Under the action of the Q-switching unit, the high-pulse-width, low-energy laser light will narrow the pulse width and instantaneously generate high-energy laser light of more than 50mJ. The control region can provide power to the laser and select the Q-switching mode of the laser. It is also connected to the computer 15, and some parameters of the laser can be controlled by software.

[0095] Long-pulse lasers refer to lasers whose output pulse duration ranges from tens of nanoseconds to several microseconds (10). -8 s–10 -6 In Q-switched solid-state laser systems, the output pulse width is typically in the tens to hundreds of nanoseconds. In unswitched or quasi-continuous wave (qμasi-CW) operation modes, microsecond-level pulses can be generated, with peak power in the MW–GW range, rather than the GW–TW range of ultrashort pulses. This makes them suitable for heating and ablation of large-area or complex materials in industrial and analytical applications. Compared to short pulses, such as… Figure 1 As shown, long-pulse lasers have lower peak power, longer pulse width, and wider plasma cooling windows, which are conducive to the formation of molecular isomers by atomic bonding and the emission of stable molecular spectra. They are suitable for ICCD105 gating with wide gate widths (μs level) to suppress the initial continuous spectrum and improve the signal-to-noise ratio of molecular spectral lines.

[0096] This embodiment uses a single long-pulse laser 1 to simultaneously perform excitation and detection, ensuring high system coordination and timing consistency, and improving experimental reproducibility and integration. Unlike other existing devices, it does not require adding a second laser and signal generator to achieve the detection effect separately.

[0097] The optical path transmission unit is used to receive long pulse laser light and reflect and focus the laser light onto the surface of the sample 13 to be tested through the multi-faceted reflector group 2, the first beam splitter 3, the dichroic mirror 4 and the microscope objective 5, while introducing the plasma emission light into the detection optical path.

[0098] Specifically, the optical path transmission unit includes: a mirror group 2, a dichroic mirror 4, a microscope objective 5, a first beam splitter 3, and a PIN tube 11.

[0099] The optical path of existing isotope measurement devices is relatively complex, using around 20 optical lenses, and some even employ dual-axis optical paths. This makes the system's collaborative operation extremely demanding, requiring rapid adjustments to the optical path to achieve the measurement needs. It cannot meet the requirements for long-term repetitive operation, and the optical path in existing devices is merely an optical path, only capable of functioning as a ship's laser or signal light. In contrast, the optical path of this invention is very simple, using only 9 optical lenses. Furthermore, the optical path of this invention can control the spectrometer 10 and the focusing unit, achieving integrated optical, mechanical, and electronic collaborative operation.

[0100] The reflector group 2 includes six reflectors. The laser emits laser light, which passes through a lifting optical path composed of two reflectors to reach two reflectors confined by a cage structure, which remains horizontal. The laser light then passes through another lifting optical path composed of two reflectors and enters the first beam splitter 3. The reflector group 2 mainly realizes the function of laser transmission.

[0101] Specifically, such as Figure 3 As shown, the reflector group 2 includes reflector I 21, reflector II 22, reflector III 23, reflector IV 24, reflector V 25, and reflector VI 26. The laser enters through reflector I 21, then enters reflector II 22, and then its path is altered by reflector III 23. It then passes through reflector IV 24 to reach reflector V 25, and finally exits from reflector V 25 through reflector VI 26, entering the first beam splitter 3.

[0102] The first beam splitter 3 is placed behind the reflector VI26. The first beam splitter 3 uses the reflection and transmission characteristics of optical thin films to split the incident light into two parts. When the beam passes through the beam splitter, part of the light is reflected and the other part passes through the beam splitter. The long-pulse laser that reaches the first beam splitter 3 will be split into two beams. One beam of light will illuminate the PIN tube 11, which will then output an electrical signal to trigger the spectrometer 10. The other beam of light will be incident on the dichroic mirror 4.

[0103] The dichroic mirror 4 is positioned below the first beam splitter 3. The dichroic mirror 4 can separate the laser used to excite the plasma from the plasma emitted light. The dichroic mirror 4 has high transmittance for 1064nm laser, ensuring that the laser can pass through efficiently and be focused onto the surface of the sample 13 to be tested. The spectral signal emitted by the plasma usually contains multiple wavelengths (such as the ultraviolet to visible light range), and the dichroic mirror 4 can reflect these lights.

[0104] The laser light passing through the dichroic mirror 4 can optionally pass through the reflector 7, as the reflector 7 can be freely removed and inserted. The main function of the reflector 7 is to reflect and transmit the light emitted by the LED light source to achieve imaging and focusing. In the absence of focus, the operator can remove the reflector 7, and the laser light passing through the dichroic mirror 4 can directly reach the microscope objective 5.

[0105] The long-pulse laser reaching the microscope objective 5 will be focused to excite the sample 13 to generate plasma. At the same time, it can be combined with the LED illumination focusing unit to produce an imaging effect. Furthermore, the molecular signal light generated by the plasma can be collected and coupled into the optical fiber for spectroscopic detection.

[0106] The PIN tube 11 is placed behind the first beam splitter 3 to receive the laser emitted by the long pulse laser 1. The photoelectric conversion output electrical signal triggers the high-precision spectrometer 10.

[0107] This invention employs a coaxial reverse collection mechanism, where excitation and signal collection share the same optical path, achieving structural simplification and efficient light energy utilization.

[0108] The LED illumination focusing unit is used to generate white light to assist the microscope in focusing; it includes LED white light illumination 6, a detachable mirror 7, and a monitoring camera 8, which are used to provide auxiliary white light illumination under the microscope objective 5 and to observe the focal plane in real time.

[0109] Specifically, the LED lighting focusing unit includes: a reflector 7, an LED white light illumination 6, and a monitoring camera 8.

[0110] The white light generated by the LED white light illumination 6 is focused by the microscope objective 5 through the reflector 7. The sample 13 to be tested is moved up and down by the three-dimensional displacement stage 9, and the surface of the sample 13 to be tested is placed on the focal plane of the microscope objective 5. The focusing effect and situation can be observed by the monitoring camera 8. When the clearest picture appears, it means that the focusing is successful.

[0111] like Figure 4 As shown, a three-dimensional displacement stage 9 is used to select different sample points by moving the stage in three dimensions. It is electrically connected to a computer 15 and is used to locate the detection point in the X / Y plane and achieve automatic or manual focusing in the Z direction. It includes an X-axis drive unit 91, a Y-axis drive unit 92 mounted on the X-axis drive unit 91, and a Z-axis drive unit 93 mounted on the Y-axis drive unit 92. It also includes a sample stage 94, which is mounted on the Z-axis drive unit 93.

[0112] like Figure 5 As shown, the sealed sample chamber unit 12 is used to fill with high-pressure inert gas at 101 kPa and to place samples; it includes a sealed chamber body 121, an optical window 122, a gas inlet and outlet 123, and a pressure control system for maintaining a high-pressure inert gas environment in the sample area. Helium and argon are preferred inert gases.

[0113] The sealed gas chamber body 121 is a sealed container made of a material with good optical transmittance and mechanical strength (such as fused silica) to contain high-pressure inert gas. The inert gas pressure is within a preset range of 101 kPa ± 1 kPa.

[0114] High-pressure inert gases effectively suppress the rapid expansion and cooling of plasma, extending its lifetime and providing more time for molecular species formation and emission, thus facilitating the capture of more complete molecular emission spectra. Secondly, the chemical stability of inert gases ensures that they will not chemically react with the sample or plasma in a high-temperature plasma environment, avoiding potential interference and improving measurement accuracy. Furthermore, high-pressure inert gases can increase plasma density and temperature, enhance emission intensity, and improve the signal-to-noise ratio, thereby increasing measurement sensitivity and precision. For example, in some experiments, using a high-pressure argon environment can extend the plasma lifetime to tens of microseconds, significantly improving the detection efficiency of molecular spectra. Using high-pressure inert gases as the environmental medium for molecular spectroscopy experiments not only optimizes plasma characteristics and enhances molecular emission signals but also improves measurement accuracy and sensitivity.

[0115] The gas inlet and outlet 123 is used to inject and discharge gas into the sealed gas chamber body 121. The inlet is connected to a high-pressure gas cylinder, and the outlet is connected to a vacuum pump.

[0116] The pressure control system unit includes pressure sensors, valves, and pressure regulators, which are used to precisely control the air pressure inside the air chamber. When the air pressure is too high, an alarm can be set to prevent accidents.

[0117] The optical window 122 is made of a material with good optical transmittance and resistance to laser damage (such as fused silica) and is used for the entry of the laser beam and the output of the spectral signal.

[0118] like Figure 6 As shown, the spectrometer 10 includes a collimating lens 108, a focusing lens 103, a planar grating 101, a grating driver 102 (which can pull the grating to rotate), and an Andor ICCD 105. It supports adjustable parameters such as external triggering, delay, gate width, and gain, and is used for molecular spectroscopy and detection.

[0119] In this embodiment, the spectrometer 10 is a Model 209 monochromator, including: an optical system, an instrument base, a grating, a wavelength driver, an ICCD105 detector, and an EMCCD107 detector. The data acquisition section uses an ICCD105 device, which has high sensitivity, strong background suppression capability, and optical signal amplification function. It can accurately capture weak emission spectral lines and is suitable for high dynamic range detection under complex background conditions.

[0120] The optical system includes: entrance and exit slits 109, collimating lens 108, focusing lens 103, and a micrometer (located inside the spectrometer; during grating rotation, the focusing lens is driven to perform micrometer-level linear translation to dynamically compensate for focus shift caused by grating wavefront error. This compensation mechanism ensures that the selected center wavelength is always accurately focused on the ICCD detection surface, effectively ensuring that the spectrometer maintains its nominal spectral resolution performance throughout the entire scanning band). The collimating lens 108 is placed at the entrance slit 109. The height and width of the entrance slit 109 can be adjusted to adjust the light flux entering the spectrometer 10, while also filtering out most of the background light to avoid interference. The collimating lens 108 collimates the molecular spectral signal light generated by the sample passing through the slit 109. The focusing lens 103 focuses the monochromatic light separated by the grating onto the camera 8 for detection. The micrometer is used to precisely adjust the position of the focusing lens 103 to achieve precise focus adjustment.

[0121] The instrument base is a cast aluminum base with a flattened top to accommodate the mirror, grating, and precision lead wire assembly. A separate casting is mounted on the base to support the grating assembly and camera accessories.

[0122] The grating is a Snap-In planar grating 101 with 1200 lines / mm, a surface area of ​​110mm×110mm, a grating area of ​​102mm×102mm, a resolution of 0.015nm, and a dispersion capability of 0.62nm / mm.

[0123] The ICCD105 detector includes an image intensifier, a CCD sensor, a gating system, and a cooling system. The photocathode converts incident photons into electrons, the MCP amplifies the electrons, and the fluorescent screen converts the electrons back into visible light. The amplified light signal is received by the CCD sensor, which receives the light signal output from the image intensifier and converts it into an electrical signal for readout and processing. The gating system incorporates a low-jitter, short-insertion-delay circuit, which precisely controls the gating time and delay of the image intensifier, ensuring synchronization with external hardware. Connecting the PIN diode 11 to the gating system allows for spectral acquisition during molecular spectroscopy generation in the plasma, filtering out most background and noise.

[0124] Computer 15 is electrically connected to long-pulse laser 1, optical path transmission unit, LED illumination focusing unit, three-dimensional displacement stage 9, and spectrometer 10. It is used to: control the emission timing and parameters of long-pulse laser 1; drive LED illumination and three-dimensional displacement stage 9 to achieve focusing and sample point switching; adjust the center wavelength and ICCD105 gating parameters of spectrometer 10 and trigger spectral acquisition; perform baseline correction, background removal and multi-peak fitting on the acquired molecular spectra, and calculate the isotope abundance and ratio of the sample 13 to be tested.

[0125] The laser emitted by the long-pulse laser 1 and the white light emitted by the LED illumination focusing unit are both focused onto the surface of the sample 13 to be tested.

[0126] Specifically, the computer unit 15 is connected to the controller of the long pulse laser 1, and can adjust the laser output frequency (1-10Hz), the laser power supply current (1-190A) and the power supply pulse width (230μs-300μs) as needed, thereby achieving a laser energy adjustment range of 0-120mJ.

[0127] The computer unit 15 is connected to the LED lighting focusing unit and the circuit displacement stage control unit. The sample surface can be observed through the camera 8. The clearer the sample surface, the better the focusing effect. Based on the image from the camera 8, the computer 15 can control the three-dimensional displacement stage 9 to achieve focusing in the Z-axis direction and selection of sampling points in the X and Y planes.

[0128] Optionally, the long-pulse laser 1 emits 1064nm laser light.

[0129] The dichroic mirror 4 transmits 1064nm laser light and reflects signal light of other wavelengths. The optical axis of the dichroic mirror 4 and the optical axis of the beam splitter form a 45° angle with the propagation path of the laser beam.

[0130] The spectrometer 10 can select wavelengths from 185 nm to 1.3 μm, has a focal plane wavelength range of 31 nm, and wavelength repeatability of ±0.05 nm.

[0131] The system's control module, the displacement controller, connects to both the computer 15 and the 3D displacement stage 9. Operators can manually focus by selecting appropriate detection points and moving the displacement stage up and down via software, using the LED illumination focusing unit and microscope objective 5. The circuit board connects to the LED light source, monitoring camera 8, and laser displacement device, and to the computer 15. Operators can switch the LED light source and monitoring camera 8 on and off via software, enabling real-time, visual focusing. During full-surface isotope detection, manual focusing can be performed at the starting point, recording the Z-axis height. Pre-scanning automatically moves the displacement stage to scan the entire surface of the laser displacement device, feeding back the Z-axis height of each point to the circuit board. During actual surface detection, the displacement stage reads the Z-axis height of each point stored in the circuit board and automatically moves up and down for autofocus. All control functions are integrated into a single software package.

[0132] The timing control module of the system: such as Figure 7 As shown, the long-pulse laser 1 emits light for excitation, and the light split by the first beam splitter 3 reaches the PIN diode 11. The PIN diode 11 then performs photoelectric conversion to output an electrical signal to trigger the spectrometer 10. Because the sample evaporates and cools to generate plasma after 1 μs of excitation, and the plasma emits molecular spectra after 2 μs, we set the integration delay of the spectrometer 10 to 3 μs and the integration time to 50 μs. In this way, the spectrometer 10 starts to turn on after receiving the electrical signal and begins to collect molecular spectra when the plasma emits them, continuing until the plasma annihilates. This reduces background spectral noise and signal noise while enhancing the molecular spectral signal.

[0133] Example 2: High-precision detection of hydrogen / deuterium isotope abundance and ratio based on molecular emission spectroscopy

[0134] Traditional laser ablation atomic absorption spectroscopy (LABAS) faces significant technical bottlenecks in hydrogen / deuterium isotope analysis. On the one hand, Stark broadening is extremely pronounced in laser-induced plumes formed under atmospheric pressure; on the other hand, laser-induced plasma (LIP) in water samples typically exhibits extremely high electron density, significantly exacerbating Stark broadening. Specifically, H… a and D a The Stark broadening factor of the emission spectral lines is already at its highest level, leading to further broadening of the spectral lines and making spectral analysis even more difficult. Although delaying the signal acquisition time can suppress broadening to some extent, the rapid decay of emission intensity over time significantly reduces the detection signal-to-noise ratio. Therefore, traditional laser ablation atomic absorption spectroscopy is insufficient to meet the requirements for high-precision D / H isotope abundance measurement in water. Furthermore, the isotope shifts in the hydrogen atomic absorption lines are extremely small, and H… a With D a The shift is only about 18 pm, which is close to the resolution limit of most conventional spectrometers, making it a challenging task to accurately distinguish H and D abundance.

[0135] In comparison, molecular spectroscopy exhibits significant advantages in isotope detection. This embodiment employs molecular spectroscopy, fully utilizing its multiple transition characteristics involving the triplet energy level structure of electronic, vibrational, and rotational states. The vibrational and rotational energy levels affect the "reduced mass" parameter. The changes are highly sensitive; the mass difference between H and D will significantly alter the composition, leading to noticeable isotopic spectral shifts. Taking the OH / OD molecule as an example, the isotopic shifts during its vibrational-rotational transitions can reach several nanometers, far exceeding the shifts in atomic spectral lines, greatly enhancing the spectral resolution of D / H differences. Furthermore, the Stark broadening effect experienced by the rotational spectral lines of the OH / OD molecule in a plasma environment is extremely weak (the experimentally measured FWHM is only 0.015 nm), resulting in extremely narrow and clearly defined spectral lines, effectively enhancing the resolution and quantitative accuracy of the molecular spectral signal. In addition, the molecular spectrum exhibits a complex "band structure" composed of multiple rotational branches. Although the spectral lines partially overlap, they provide rich high-dimensional information for multivariate statistical analyses (such as partial least squares regression, PLSR). OH and OD are hydroxyl radicals naturally generated during laser ablation of water samples. Their molecular emission spectra directly reflect the D / H isotopic composition of the sample, requiring no chemical derivatization, enabling in-situ, non-destructive direct detection of the original sample.

[0136] The pulse width of long-pulse lasers is matched with the timescale of molecular bond dissociation and formation, allowing the H and D atoms released from the sample to fully react with O atoms in the water, generating OH / OD molecules in high yield. Long-pulse laser ablation produces lower atomic spectral line densities and less overlap in the near-ultraviolet band, which is beneficial for subsequent molecular spectrum extraction. Simultaneously, the resulting plasma decays slowly, maintaining a stable temperature of 7000 K and an electron density as high as 10¹⁸. 7 cm - 3. It promotes the generation of excited-state molecules and prolongs their emission lifetime. In addition, the plasma induced by long-pulse laser has a weak shock wave and a vertically extended geometry, which effectively suppresses the entry of external oxygen and improves the reactant transport efficiency; the residual energy at the end of the laser pulse further induces secondary evaporation, providing a continuous source of reactants for the generation of OH / OD molecules, thus forming a cascade amplification effect of molecular emission.

[0137] To enhance molecular signal intensity and improve experimental repeatability and detection accuracy, this embodiment uses argon as the carrier gas. First, the chemical inertness of argon ensures it does not react with the matrix or analyte molecules, effectively isolating reactive components in the air (such as oxygen, nitrogen, and water vapor). This avoids non-target reactions (such as oxidation, nitridation, or hydration reactions) induced by the high-temperature environment created by laser ablation, ensuring pure and interference-free OH and OD signals. Second, in the high-temperature plasma, argon excites the emission states of free radicals and molecules in the plasma through processes such as Penning ionization and energy transfer, enhancing the OH / OD emission intensity. Excited argon atoms (Ar*) are formed through electron collisions, further transferring energy to OH / OD, enabling them to transition to the radiation state with a high probability and without additional energy loss. In addition, the high heat capacity and low thermal conductivity of argon gas enable a moderate plasma cooling rate, reducing the occurrence of OH / OD recombination or hydrogen-oxygen exchange and suppressing isotope fractionation. At the same time, the gas flow structure of argon gas promotes uniform diffusion of laser ablation particles, improves spatial uniformity, and enhances signal stability and repeatability.

[0138] During the experiment, hydroxyl radicals (OH) generated by laser ablation in moist argon gas... The transition produces the strongest molecular emission signal, and this band contains six main branches (Q). 11 R 11 P 11 Q 22 R 22 P 22 ) and 6 satellite branches ( 1 Q 12 , 0 P 12 , 0 R 12 , 0 P21 , R Q 21 , s R 21 The Q branch has the highest Hund-London factor and the strongest emission. Therefore, this invention selects the Q branch in the wavelength range of 306–310 nm. 00 Branches were used as targets for molecular spectral acquisition. Experimental results showed that when the argon flow rate was increased to 10 L / min, the signal intensity of the rotational structure in the blank spectrum was significantly reduced, decreasing to <0.1% of the water sample signal, thus significantly suppressing background interference. For OH molecule emission, the acquisition delay time was set to >2 μs to eliminate strong background fluctuations in the early plasma. Observations showed that the net molecular emission intensity increased with time before 8 μs, then rapidly decayed, and the background and noise tended to stabilize after 12 μs. The signal approached the background value at 30 μs, and the SBR and SNR reached their maximum at 8 μs. Therefore, subsequent experiments fixed the acquisition conditions at a delay of 8 μs and a gate width of 50 μs.

[0139] Specifically, plasma is generated by exciting the sample 13 with a single long-pulse laser. The nanoscale isotope shift characteristics of molecular spectra such as OH / OD are utilized, combined with interference suppression in a high-pressure inert gas environment, to achieve in-situ detection of isotope abundance ratios. Specific steps may include:

[0140] A1. Fill a sealed environment with a high-pressure inert gas at a predetermined pressure and place the sample to be tested 13.

[0141] Specifically, the sample to be tested 13 is placed in a sealed sample chamber unit 12, which includes a sealed gas chamber body 121, a gas inlet and outlet 123, a pressure control system, and an optical window 122. Argon gas (high-pressure inert gas) at 101 kPa is introduced into the chamber, and the pressure control system maintains stable gas pressure, suppresses non-target chemical reactions, and stabilizes the plasma temperature. The high heat capacity of the inert gas is used to delay plasma cooling and promote the efficient generation of OH / OD molecules.

[0142] Argon is a chemically inert gas that can isolate air and enhance molecular spectral signals through Penning ionization.

[0143] A2. Emit a long-pulse high-energy laser with an energy greater than a predetermined value, and reflect the long-pulse high-energy laser to focus the high-energy laser onto the surface of the sample 13 to excite the sample 13 to plasma; the long-pulse high-energy laser is a laser pulse with a predetermined duration.

[0144] Start the 1064nm long pulse laser 1 and adjust the output frequency to 1Hz, pulse width to 104ns, and energy to 80mJ (achieved by adjusting the supply current from 1 to 190A and the supply pulse width from 230 to 300μs).

[0145] The laser beam is transmitted to the first beam splitter 3 via the reflector group 2 and split into two beams: one beam triggers the PIN tube 11 of the spectrometer 10, and the other beam is transmitted through the dichroic mirror 4 and focused onto the sample surface by the microscope objective 5, forming a light spot with a diameter ≤50μm, which excites and generates plasma.

[0146] A3. After the surface of the sample 13 to be tested is excited by the plasma, the corresponding molecular spectral signal is acquired and molecular spectral detection analysis is performed to realize the detection of the abundance ratio of isotopes.

[0147] When the plasma is cooled to 5000-8000K, the emitted molecular spectrum (such as the 306-310nm band of OH / OD) first passes through the fused silica optical window 122 and then is reflected by the dichroic mirror 4 into the spectrometer 10.

[0148] A Model209 monochromator (1200 lines / mm grating, 0.015nm resolution) was used, and an ICCD105 detector was set with a delay of 8μs and a gate width of 50μs. The spectral signal was acquired under the triggering of PIN tube 11.

[0149] The collected data underwent asymmetric least squares (AsLS) baseline correction and statistically sensitive nonlinear iterative peak (SNIP) background removal sequentially. Voigt line fitting was then performed using molecular constants (such as rotation / vibrational constants) from the HITRAN database, and isotopic abundance ratios were calculated via partial least squares regression (PLSR). The data analysis involved two methods: one was molecular spectral fitting, which involved AsLS baseline correction, SNIP background removal, and Voigt line fitting using molecular constants (such as rotation / vibrational constants) from the HITRAN database. The second method involved measuring molecular emission spectra from different known standard samples, preprocessing the spectral data (background removal, smoothing), building a PLSR model using the preprocessed spectral data, determining the optimal number of principal components using cross-validation (such as leave-one-oμt or k-fold), and using the optimized model to predict the abundance ratios of unknown samples.

[0150] Objective: In the spectrum y i Upper-fit smoothed baseline z i This makes the residuals more sensitive to negative biases. Optimization objective:

[0151]

[0152] Among them, weight

[0153]

[0154] • λ: Smoothing parameter; the larger the value, the smoother the baseline (typical value 10).2 ~10 9 ).

[0155] • p: Asymmetric penalty parameter, ranging from (0,1), typically p≈10 -2 Up to 10 -1 .

[0156] • Number of iterations: Generally 10-20 times, until the weights converge.

[0157] AsLS baseline correction

[0158] Objective: To gradually "sharpen" the background and retain narrow peaks through iterative local minima. Algorithm core (pseudocode):

[0159] 1. Assume the original spectrum 2. For iteration steps k = 1 to K:

[0160]

[0161] Where the window half-width m varies with k, it can be set to

[0162] 3. Final Background Estimation Signal s after subtraction i =y i -b i .

[0163] K: Total number of iterations, commonly 20-100.

[0164] • Window growth strategy: can grow linearly or square root, affecting the smoothness of the background.

[0165] SNIP background removal

[0166] The Voigt function is a convolution of Gaussian and Lorentz functions, used to describe both Doppler broadening and optical broadening simultaneously.

[0167]

[0168] in

[0169]

[0170] A: Peak intensity (area or peak height)

[0171] x0: Peak center position.

[0172] σ: Gaussian width parameter (compared to half-width at half-height) (Related).

[0173] -γ: Lorentz width parameter (half-width, H) L =2γ).

[0174] When fitting, it is necessary to optimize {A,x0,σ,γ} simultaneously, and the nonlinear least squares (Levenberg-Marqμardt) algorithm is commonly used.

[0175] Voigt spectral line fitting model expression: X∈R n×p (spectral matrix) and Y∈R n×q The (concentration / abundance matrix) is decomposed into:

[0176]

[0177]

[0178] W: Weight matrix, each column is the weight vector of the h-th component.

[0179] P, Q: Load matrices, corresponding to X and Y respectively.

[0180] T, M: Score matrix.

[0181] Number of components H: Number of principal components (latent variables).

[0182] Cross-validation metrics: RMSECV, R 2 Used to select the optimal H.

[0183] PLSR

[0184] A4. Autofocus and Sample Positioning

[0185] The LED illumination focusing unit is activated, and its built-in white light source is reflected by the reflector 7 and focused onto the surface of the sample 13 under test by the microscope objective 5, forming an illumination spot. The computer 15 drives the three-dimensional displacement stage 9, causing the sample stage 94 to move in the X / Y plane to select the detection area, and simultaneously adjusts the Z-axis height.

[0186] The system acquires images of the surface of the sample 13 in real time using camera 8. When the image texture clarity reaches a threshold (such as the grayscale gradient peak), the system determines that the focus is complete, with an accuracy of ±5μm. The system automatically records the three-dimensional coordinates of the current detection point for path planning of subsequent multi-point detection.

[0187] A5. System Calibration

[0188] A heavy water standard with a known D / H ratio (e.g., D / H = 0.0156) was used as the calibration sample and placed in a sealed sample chamber. The energy of the long-pulse laser 1 was adjusted to 80 mJ and the output frequency was 1 Hz. The laser energy was calibrated using a power meter. The center wavelength of the spectrometer 10 was set to 310 nm (the characteristic peak band of OH molecules), and the ICCD105 detector was set with a delay of 8 μs and a gate width of 50 μs. The spectrum of the standard was then acquired.

[0189] Energy scanning experiments were conducted, and the power supply current was adjusted (1-190A) to achieve an OH / OD spectral signal-to-noise ratio ≥200:1, while simultaneously optimizing optical path transmission efficiency. A partial least squares regression (PLSR) model was established based on the standard sample spectrum to verify a detection limit ≤0.1% and repeatability error <2%, ensuring industrial-grade detection accuracy. Results are as follows... Figure 9 and Figure 10 As shown.

[0190] Example 3: High-precision detection of CC isotope abundance and ratio based on molecular emission spectroscopy

[0191] 1. First, the benzoic acid sample enriched with C2 isotopes is placed in a sealed sample chamber. The chamber is then closed. Argon is chosen as the inert gas. Compared to air or nitrogen, the plasma generated by laser ablation in argon has a longer high-temperature holding time. This is because argon, as an inert gas, has low thermal conductivity, which effectively slows down energy loss. Meanwhile, nitrogen readily undergoes molecular dissociation at high temperatures, consuming a large amount of energy in the process, and further dissipating energy through its complex intramolecular degree-of-freedom channels. Furthermore, nitrogen atoms in the excited state exhibit certain chemical reactivity, leading to further energy loss. Argon, on the other hand, does not participate in chemical reactions, which helps maintain a higher energy state in the plasma. In this environment, the formation of C2 does not depend on reactions with atmospheric components, making argon a more ideal background gas. It can provide sufficient energy in the gas phase of the ablation plume, allowing the material to fully dissociate and reach thermodynamic equilibrium within a longer time. Overall, an argon atmosphere is more conducive to the complete atomization of the ablation plume, thereby improving analytical accuracy and plasma stability. Connect the inlet of the sealed sample chamber to the argon cylinder, open the valve of the argon cylinder, and observe the pressure gauge of the gas chamber. When the argon pressure in the sealed sample chamber reaches 101 kPa, the gas chamber will automatically close the gas inlet, ensuring that the argon pressure inside the chamber remains at 101 kPa.

[0192] 2. Rotate the reflector on the spectrometer 10 clockwise, select the ICCD105 camera 8, open the ICCD105 software on the computer 15, and wait for it to cool down to -20℃. Connect the 209 spectrometer 10, select wavelength as the abscissa, select 1200 grating lines, and set the detection center wavelength to 475nm. The center wavelength must match the current dial reading. Select external trigger mode for the ICCD105, and set the exposure time to 100μs. Set the ICCD105 delay to 5.5μs, gate width to 70μs, gain to 4000, and configure the data save path and format.

[0193] 3. Place the sealed sample chamber on the sample stage 94, and use the computer 15 to control the three-dimensional displacement stage 9 to move in the X and Y planes. Select a suitable sample point, then turn on the LED lighting source, insert the reflector 7, and observe the sample surface through the camera 8. Move the Z-axis of the displacement stage. When the clearest image of the sample surface appears in the camera 8, it means that the focus has been completed. Then turn off the LED light source and remove the reflector 7.

[0194] 4. Turn on the long pulse laser 1, adjust the frequency of the long pulse laser 1 to 10 Hz and the pulse width to 104 ns, place the power meter probe at the long pulse laser port, adjust the laser power supply current to adjust the energy of the long pulse laser until the energy of the long pulse laser is 100 mJ, turn off the laboratory lights, turn on the ICCD105 of the spectrometer 10, then adjust the laser frequency to 1 Hz and start emitting long pulse laser.

[0195] 5. The long-pulse laser first passes through the reflector group 2 and reaches the first beam splitter 3. At this time, the laser will be split into two beams. One beam passes through the first beam splitter 3 and enters the PIN tube 11. The PIN tube 11 will output an electrical signal to the spectrometer 10, which can trigger the detection and achieve coordinated operation without triggering the spectrometer 10 to start collecting spectra. The other laser beam will be reflected by the first beam splitter 3 and enter the dichroic mirror 4. The long-pulse laser will pass through the dichroic mirror 4 and enter the microscope objective 5. The microscope objective 5 will focus the long-pulse laser onto the surface of the sample 13 to be tested, thereby increasing the instantaneous peak power density of the long-pulse laser and thus breaking down the sample 13 to be tested.

[0196] 6. When the sample 13 is broken down, it will instantly vaporize to form a high-energy plasma. During the cooling process, the plasma will first continuously radiate a full-spectrum signal, then emit atomic spectra after 1 μs, and after 2 μs, the atoms will combine to form molecules, thus radiating molecular spectra. Because of the mass difference between the isotopic isomers, a shift in the molecular emission band will occur, with a band shift of about 0.1 nm. The resolution of the spectrometer 10 is 0.015 nm.

[0197] 7. The molecular spectrum emitted by the plasma is reflected by the dichroic mirror 4 to the coupling mirror. The signal spectrum is coupled into the optical fiber. Then, the signal light in the optical fiber is incident on the collimating mirror 108 inside the spectrometer 10 through the slit 109. The collimated parallel light reaches the grating with 1200 gratings. The grating separates the composite light into monochromatic light with a center wavelength of 475nm. The monochromatic light is focused onto the surface of the ICCD 105 by the focusing lens 103.

[0198] 8. When triggered by PIN tube 11, ICCD105 is in working condition. The molecular light signal after spectral splitting can be detected and observed in camera 8.

[0199] 9. Export the collected molecular spectral data for data processing. First, perform baseline correction and background removal on the data. Use asymmetric least squares (AsLS) and SNIP. AsLS and SNIP can be used to estimate and remove slowly changing background.

[0200] 10. Subsequently, polynomial fitting and automatic background correction are performed. Continuous wavelet transform combined with interpolation can efficiently remove residual baselines.

[0201] 11. Import the processed data into Pgopher software, select wavelength as the horizontal axis unit, and ensure that the data is displayed in a two-dimensional graph, showing the total information of the data.

[0202] 12. Loading molecular constants include: rotational constant and vibrational constant. The loading line list contains the spectral line data of the molecules.

[0203] 13. Open the fitting settings window, select the rotation constant and vibration constant parameters to be fitted, and set the initial guess value and fitting range.

[0204] 14. Use automatic molecular spectroscopy fitting, observe the fitting results, and check the residuals and intensity residuals.

[0205] 15. Examine energy level state information and spectral transition information. Use software to calculate the abundance and ratio of isotopes. Results are as follows: Figure 11 As shown.

[0206] Example 4: High-precision detection of OH isotope abundance and ratio based on molecular emission spectroscopy

[0207] 1. Use ordinary water ice as 16 A reference sample for OH molecular isotopes; heavy water ice is used for research. 16 OD molecular isotope spectra 18 O-enriched ice is used for measurement 18 OH isotopes.

[0208] 2. The sealed sample chamber 14 is filled with argon gas.

[0209] 3. The center wavelength of the spectrometer 10 is set to 310nm, the delay of the ICCD105 is 8μs, and the gate width is 50μs.

[0210] 4. The energy of the long pulse laser 1 is set to 80mJ.

[0211] The other operations are the same as in Example 3. The results are shown in Figure 12. Figure 13 It is a contrast of air atmosphere, from Figure 12 and Figure 13 The results show that by filling the plasma with argon or helium at 101 kPa, this invention extends the plasma lifetime to 50-100 μs, increases molecular emission intensity by 3 times, and achieves a signal-to-noise ratio of 200:1, far exceeding the 80:1 of other commonly used measurement systems. The 104 ns pulse width of the long-pulse laser 1 provides sufficient energy to ablate the sample while avoiding the plasma transient instabilities caused by femtosecond lasers. Molecular spectra are acquired with a 2-5 μs delay, effectively avoiding atomic line interference. Combined with the spectrometer 10, the isotope abundance detection limit is as low as 0.1%, better than the 0.5-1% of existing commonly used measurement systems. The repeatability error of this invention is less than 2%, meeting the high-precision requirements for industrial applications.

[0212] Example 5: High-precision detection of CN isotope abundance and ratio based on molecular emission spectroscopy

[0213] 1. Using N isotope-enriched benzamide particle samples as... 14 N、 15 N reference sample, decanoic acid powder as 12 C 13 C is the reference sample.

[0214] 2. Helium is selected as the inert gas for the sealed sample chamber 14. Helium is lightweight and chemically inert, which is suitable for quickly removing ambient gases and reducing intermolecular collision interference. In addition, helium has high thermal conductivity, which can accelerate plasma cooling and promote molecular recombination.

[0215] 3. The center wavelength of the spectrometer 10 is set to 420nm, the delay of the ICCD105 is 40μs, and the gate width is 100μs.

[0216] 4. The energy of the long pulse laser 1 is set to 32mJ.

[0217] The other operations are the same as in Example 3. The result is as follows: Figure 14 As shown.

[0218] The embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A device for detecting isotopic abundance and ratio based on molecular emission spectroscopy, characterized in that, include: A single long-pulse laser (1) is used to emit laser pulses with a pulse width ≥100ns, a frequency of 1~10HZ, and an energy of 0~120mJ to excite the sample to be tested (13) to generate plasma; The optical path transmission unit is used to receive long pulse laser and reflect and focus the laser onto the surface of the sample to be tested (13) through the reflector group (2), the first beam splitter (3), the dichroic mirror (4) and the microscope objective (5), while introducing the plasma emission light into the detection optical path. The LED illumination focusing unit includes LED white light illumination (6), a reflector (7) and a monitoring camera (8), which are used to provide auxiliary white light illumination under the microscope objective (5) and to observe the focal plane in real time. A three-dimensional displacement stage (9) is connected to a computer (15) for positioning detection points in the X / Y plane and achieving automatic or manual focusing in the Z direction; The sealed sample chamber unit (12) includes a sealed gas chamber body (121), an optical window (122), a gas inlet and outlet (123) and a pressure control system, used to maintain a high-pressure inert gas environment in the area of ​​the sample to be tested (13); The spectrometer (10) includes a collimating lens (108), a focusing lens (103), a planar grating (101), a grating driver (102), and an ICCD (105), and supports adjustable parameters such as external triggering, delay, gate width, and gain, for molecular spectroscopy and detection. A computer (15) is connected to a long-pulse laser (1), an optical path transmission unit, an LED illumination focusing unit, a three-dimensional displacement stage (9), and a spectrometer (10) to control the emission timing and parameters of the long-pulse laser (1); drive the LED illumination focusing unit and the three-dimensional displacement stage (9) to achieve focusing and sample point switching; adjust the center wavelength of the spectrometer (10) and the gate parameters of the ICCD (105) and trigger spectral acquisition; perform baseline correction, background removal and multi-peak fitting on the acquired molecular spectra, and calculate the isotopic abundance and ratio of the sample (13) to be tested.

2. The isotope abundance and ratio detection device based on molecular emission spectroscopy according to claim 1, characterized in that, The long-pulse laser (1) includes: Pump cavity, used to provide pump energy for the laser medium and achieve population inversion; An acousto-optic Q-switching cavity includes a transducer, power supply, acousto-optic medium, sound-absorbing material, and cooling system. It achieves instantaneous laser release through Q-switching via acousto-optic diffraction. The laser controller and its supporting software are used to adjust the pump source drive, Q-switch trigger and laser output parameters, and communicate with the computer (15).

3. The isotope abundance and ratio detection device based on molecular emission spectroscopy according to claim 1, characterized in that: The mirror group (2) includes 6 mirrors. The long pulse laser (1) emits laser light, which passes through the lifting optical path formed by two mirrors to reach the two mirrors constrained by the cage structure. The cage structure remains horizontal. The laser light then passes through the lifting optical path formed by two mirrors and enters the beam splitter. One beam of light illuminates the PIN tube, and the other beam of light passes through the dichroic mirror (4) and is focused onto the surface of the sample to be tested (13) by the microscope objective (5).

4. The isotope abundance and ratio detection device based on molecular emission spectroscopy according to claim 3, characterized in that: The first beam splitter (3) is placed behind the last reflector. The first beam splitter (3) uses the reflection and transmission characteristics of optical thin film to split the incident light into two parts. When the beam passes through the first beam splitter (3), part of the light is reflected and the other part of the light passes through the first beam splitter (3). The transmitted light shines on the PIN tube and the reflected light is incident on the dichroic mirror (4). The dichroic mirror (4) is positioned below the first beam splitter (3), and the dichroic mirror (4) can separate the excitation laser from the plasma emission light; The reflector (7) is detachably installed below the dichroic mirror (4). The reflector (7) is used to reflect the light source emitted by the LED light source to achieve imaging and focusing. In the absence of focus, the operator can remove the reflector (7), and the laser passing through the dichroic mirror (4) can directly reach the microscope objective (5). The long pulse laser reaching the microscope objective (5) will be focused to excite the sample (13) to generate plasma. After the reflector (7) is installed, it can be used with the LED illumination focusing unit to produce imaging effect. Moreover, the molecular signal light generated by the plasma can be collected and coupled into the optical fiber for spectroscopic detection.

5. The isotope abundance and ratio detection device based on molecular emission spectroscopy according to claim 1, characterized in that: The spectrometer (10) includes a PIN tube trigger circuit. The PIN tube receives the laser pulse transmitted by the first beam splitter (3) and outputs a trigger signal to realize external trigger acquisition of ICCD (105). The delay is set to 2-50μs and the gate width is set to 20-150μs.

6. The isotope abundance and ratio detection device based on molecular emission spectroscopy according to claim 1, characterized in that: The pressure control system of the sealed sample chamber unit (12) includes a pressure sensor, a regulating valve and a safety alarm device, which are used to monitor and maintain the inert gas pressure within a preset range of 101 kPa ± 1 kPa in real time.

7. The isotope abundance and ratio detection device based on molecular emission spectroscopy according to claim 1, characterized in that: The computer (15) can call molecular spectroscopy fitting software, load the rotation-vibration constant and spectral line list, automatically complete the fitting of multiple spectral peaks and output the isotope abundance and ratio.

8. A method for detecting isotopic abundance and ratio based on molecular emission spectroscopy, characterized in that, The isotope abundance and ratio detection device based on molecular emission spectroscopy as described in any one of claims 1-7 includes the following steps: (1) Placement of the sample to be tested (13): Place the isotopically enriched sample (13) particles into the sealed sample chamber unit (12) and adjust the inert pressure to 101kPa±1kPa. (2) Microscopic focusing: Turn on the LED white light illumination (6) and drive the three-dimensional displacement stage (9) to make the surface of the sample (13) coincide with the focal plane of the microscope objective (5); (3) Plasma excitation: The long pulse laser (1) is triggered according to the set working frequency and energy, and focused onto the surface of the sample (13) to be tested through the optical path transmission unit to generate plasma; (4) Spectral acquisition: The plasma begins to emit molecular spectra 2-15 μs after excitation. The signal is reflected by the dichroic mirror (4) and coupled into the optical fiber. Under the trigger of the PIN tube, the wavelength in the spectrometer (10) and the ICCD (105) are adjusted to acquire the spectrum at a gate width of 30-150 μs. (5) Data processing: Apply AsLS and SNIP algorithms to the original spectra to perform baseline correction and background removal, and then analyze the molecular spectra of isotopes through multi-peak fitting. (6) Isotope calculation: Call the molecular spectroscopy fitting software, load the list of molecular constants and spectral lines, automatically fit and output the isotope abundance and ratio of the sample to be tested (13).

9. The isotope abundance and ratio detection method according to claim 8, characterized in that, The AsLS and SNIP algorithms can be used individually or in combination, and residual baselines can be further removed by continuous wavelet transform and interpolation.

10. The isotope abundance and ratio detection method according to claim 8, characterized in that, The spectrometer (10) has a center wavelength in the range of 190 to 800 nm, which is driven by a stepper motor and a sine arm to scan the grating. The wavelength repeatability is ±0.005 nm.

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