Atmospheric cl intermediates generation and detection system and detection method based on laser photolysis-infrared spectroscopy combined technology

Abstract

The application discloses a laser photolysis-infrared spectrum combined technology-based atmospheric cl intermediates generation and detection system and a detection method, and the system comprises a low-pressure flow tube sampling module, a excimer laser photolysis module, a high-vacuum ultralow-temperature reaction cell module and an in-situ Fourier transform infrared spectrum detection module; the low-pressure flow tube sampling module is used for conveying mixed gas to the high-vacuum ultralow-temperature reaction cell module; the excimer laser photolysis module is used as a photolysis source and is guided to the high-vacuum ultralow-temperature reaction cell module through an optical path; and the in-situ Fourier transform infrared spectrum detection module is used for collecting and analyzing infrared spectrum of a captured sample on a cesium iodide cold window surface of the high-vacuum ultralow-temperature reaction cell module. Through the low-pressure flow tube premixing and the working mode of "photolysis and deposition simultaneously", the application can efficiently and in-situ generate CIs in an ultralow-temperature matrix isolation environment, and realize high-sensitivity and high-specificity infrared detection.

Description

Technical Field

[0001] This invention belongs to the field of environmental monitoring and analysis instruments and equipment, and relates to a system and method for generating and detecting atmospheric Kreutz intermediates based on laser photolysis-infrared spectroscopy technology. Specifically, it relates to a laboratory detection system and method for generating, capturing and detecting highly reactive, transient atmospheric key reactive intermediates—Kreutz intermediates. Background Technology

[0002] Secondary pollution, characterized by ozone (O3) pollution, has become a key issue in my country's air pollution control. Krohler intermediates (CIs), as key reactive intermediates in the ozone degradation process of volatile organic compounds (VOCs), play a crucial role in atmospheric chemistry, and their concentration and reaction pathways profoundly affect atmospheric oxidation, secondary aerosol formation, and greenhouse gas lifetimes. Therefore, accurately characterizing the concentration and sources of CIs is of great significance for scientifically assessing their environmental effects and formulating precise pollution control strategies.

[0003] However, the transient nature (extremely short lifetime), high reactivity, and low concentration of cis (citric acid molecules) pose significant technical bottlenecks to their direct experimental characterization. In the laboratory, cis are typically generated by photolysis of diiodoalkanes in an excess O2 atmosphere using ultraviolet light. Current mainstream detection methods, such as vacuum ultraviolet photoionization mass spectrometry (VUV-MS) and ultraviolet absorption spectroscopy (UV), have obvious limitations: VUV-MS relies on expensive and rare synchrotron radiation sources; and UV methods have wide and overlapping absorption spectra, making it difficult to effectively distinguish structurally similar cis species. These technical bottlenecks severely restrict the systematic study and accurate measurement of cis. Infrared spectroscopy possesses a unique "fingerprint" recognition capability for molecular structures, making it an ideal tool for distinguishing cis (especially cis-trans isomers). Matrix-isolated Fourier transform infrared spectroscopy (MI-FTIR) has been proven effective for capturing and measuring cis. However, existing technical approaches suffer from fundamental technical flaws: in traditional MI-FTIR experiments involving "deposition followed by photolysis," when photolyzing diiodoalkane precursors deposited in an ultra-low temperature matrix, the primary photolysis product CH2I cannot effectively react with the co-deposited O2 to remove iodine atoms, resulting in extremely low or even non-existent yields of crucial CI intermediates such as CH2OO. This bottleneck severely restricts the application of MI-FTIR technology in CI research. Summary of the Invention

[0004] To address the aforementioned technical challenges, this invention constructs an infrared spectroscopy measurement system combining excimer laser photolysis and matrix isolation technologies. It innovatively introduces a low-pressure flow tube premixing and a "photolysis-deposition-while-depositing" working mode, enabling efficient, in-situ generation of chromium compounds (CIs) in an ultra-low temperature matrix isolation environment, and achieving a highly sensitive and specific infrared detection system. This invention's CI generation and detection system, based on the combined use of 248nm excimer laser photolysis and matrix isolation-Fourier transform infrared spectroscopy (MI-FTIR), can achieve efficient generation and accurate identification of CIs with different structures, providing a reliable technical platform for the study of atmospheric reactive intermediates.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A system comprising a low-pressure flow tube injection module, an excimer laser photolysis module, a high-vacuum ultra-low temperature reaction cell module, and an in-situ Fourier transform infrared spectroscopy detection module; The low-pressure flow tube injection module is used to mix and deliver diiodoalkane precursor vapor, O2 and dilution carrier gas to the high-vacuum ultra-low temperature reaction cell module. The excimer laser photolysis module serves as the photolysis source and is guided to the high vacuum ultra-low temperature reaction cell module via an optical path. The in-situ Fourier transform infrared spectroscopy detection module is used to acquire and analyze the infrared spectrum of the sample captured on the surface of the cesium iodide cold window of the high vacuum ultra-low temperature reaction cell module, so as to achieve accurate identification and quantitative analysis of the functional group structure of CIs.

[0006] According to an embodiment of the present invention, the cesium iodide cold window surface of the high vacuum ultra-low temperature reaction cell module is used to capture the sample, and the cesium iodide cold window surface of the high vacuum ultra-low temperature reaction cell module is perpendicular to the gas outlet of the low pressure flow tube injection module and parallel to the laser outlet of the excimer laser photolysis module.

[0007] The core innovation of this invention lies in integrating pulsed excimer laser in-situ photolysis technology with MI-FTIR and adopting a new "photolysis-deposition simultaneous" working mode, fundamentally solving the technical problem that laser photolysis methods cannot generate CIs in low-temperature matrices. A further innovation is the introduction of a low-pressure flow tube injection module to replace the traditional flowmeter injection method. By precisely controlling the system pressure (approximately 100 Torr), the low-pressure environment promotes the diffusion and collision of precursor gas molecules, resulting in more uniform mixing before entering the reaction zone within the high-vacuum, low-temperature matrix cavity, effectively avoiding excessively high or low local concentrations. Furthermore, it effectively reduces the inflow rates of the three reaction gases—diiodoalkane precursor vapor, O2, and dilution carrier gas—thereby extending the gas phase residence time of the precursor in the laser-acting region, ensuring high photolysis efficiency.

[0008] The system works as follows: The reaction gas mixture (diiodoalkane vapor / O2 / Ar) is photolyzed in situ by a high-energy 248nm excimer laser the instant it enters the ultra-high vacuum, high-vacuum, low-temperature matrix cavity, generating high-concentration CIs instantaneously through the following reaction pathway:

[0009] The gaseous products (including CIs) generated by photolysis are then rapidly condensed and captured on a cesium iodide cold window at approximately 4-15 K, and frozen in an inert matrix, thereby inhibiting their subsequent reactions and achieving stable enrichment.

[0010] According to an embodiment of the present invention, the low-pressure flow tube injection module is provided with a vacuum gauge, a butterfly valve, a first air inlet, a second air inlet, and a third air inlet; The first air inlet, the second air inlet and the third air inlet are located at one end of the low-pressure flow pipe, and the other end of the low-pressure flow pipe is connected to a butterfly valve and a mechanical pump. The vacuum gauge is positioned in the middle of the low-pressure flow tube; The diiodoalkane precursor is delivered to the low-pressure flow tube injection module via the first inlet using an inert gas bubbling method. O2 is delivered to the low-pressure flow tube injection module via the second air inlet; The diluted carrier gas is delivered to the low-pressure flow tube injection module through the third air inlet.

[0011] In some embodiments, mass flow meters are respectively installed on the intake pipes of the first air inlet, the second air inlet, and the third air inlet.

[0012] To ensure the stability of gas transport within the low-pressure flow tube, the inner diameter of the tube and the total gas flow rate preferably meet laminar flow conditions. Preferably, the gas flow state within the low-pressure flow tube satisfies the requirement that the Reynolds number is below the laminar critical value to avoid concentration fluctuations and uneven mixing caused by turbulence. Preferably, the inner diameter of the low-pressure flow tube is 10-15 mm, for example, 12 mm; the length is 70-80 cm, for example, 75 cm. Low-pressure flow tubes of these dimensions provide sufficient mixing and transport time for each component, thereby ensuring the concentration stability and uniformity of the output gas flow.

[0013] According to an embodiment of the present invention, the system further includes a diiodoalkane precursor storage module, which is provided with an inert gas inlet pipe and an outlet pipe, the inert gas inlet pipe extending below the liquid surface of the diiodoalkane precursor. To maintain a stable evaporation rate of the CH3CHI2 precursor, the diiodoalkane precursor storage module (e.g., a bubble flask) is placed in a constant temperature water bath at 25-35°C (e.g., 25°C).

[0014] This invention precisely controls the mixing ratio and flow rate of diiodoalkane precursors and O2, and achieves premixing in a low-pressure flow tube. A vacuum gauge, butterfly valve, and mechanical pump are installed sequentially in the middle of the flow tube to maintain the pressure at ~100 Torr, thereby controlling the gas intake of reactants and optimizing enrichment and photolysis time, ensuring that the reactants are delivered to the core reaction area of ​​the high-vacuum cryogenic reaction cell module in a stable and controllable manner.

[0015] According to an embodiment of the present invention, the excimer laser photolysis module uses a 248nm excimer laser as the photolysis source. The laser beam emitted by the 248nm excimer laser is perpendicular to the path of the mixed gas being sprayed onto the cold window and parallel to the surface of the cold window. For example, the laser beam emitted by the 248nm excimer laser is focused by a concave mirror and reflected into the path area of ​​the mixed gas being sprayed onto the surface of the cold window. By adjusting the laser incident angle and the optical path position, the laser mainly acts on the gas-phase mixture in front of the cold window, avoiding direct laser irradiation of the cold window surface. Guided by the optical path, the precursor can be efficiently photolyzed in the core region of the high-vacuum cryogenic reaction cell module (high-vacuum cryogenic matrix cavity) during the brief process of gas being sprayed onto the cold window, instantaneously generating a high concentration of target CIs, thus realizing the in-situ generation of active intermediates.

[0016] According to an embodiment of the present invention, the high-vacuum cryogenic reaction cell module includes a high-vacuum cryogenic matrix chamber, a molecular pump assembly, and a closed-loop liquid helium cooling system (such as a closed-loop helium refrigerator). The gas inlet of the high-vacuum cryogenic matrix chamber is perpendicular to the cesium iodide cold window. The closed-loop liquid helium cooling system provides the molecular pump assembly with a cryogenic temperature (approximately 4-15 K) and a temperature (better than 4 × 10⁻⁶ K). -4 The module operates in an ultra-high vacuum environment (Pa). It not only captures samples, but its extreme conditions also ensure that active intermediates are "frozen," providing a prerequisite for high signal-to-noise ratio detection.

[0017] In some embodiments, the distance between the gas inlet of the high-vacuum cryogenic matrix cavity and the cesium iodide cold window is 1.50-2.0 cm, for example, 1.50 cm. By adjusting the position of the cesium iodide cold window in the high-vacuum cryogenic matrix cavity so that its surface faces the gas inlet and the distance between the cold window and the gas inlet is 1.50-2.0 cm, within this distance range, the 248 nm excimer laser can effectively photolyze the mixed gas in the gas phase region in front of the cold window, thereby generating the target CIs. The 248 nm excimer laser beam is focused by a concave mirror and reflected into the path region where the mixed gas is sprayed onto the surface of the cold window. The laser incident angle and optical path position are adjusted so that the laser mainly acts on the gas phase mixture in front of the cold window, avoiding direct laser irradiation of the cold window surface to prevent affecting the effective generation of CIs. After completing the adjustment of the optical path, gas inlet distance, and spray angle, the gas inlet valve and excimer laser are opened. The mixed gas is photolyzed in front of the cold window to generate products such as CH2OO, which are then rapidly deposited on the surface of the cold window.

[0018] According to an embodiment of the present invention, the high-vacuum low-temperature matrix cavity is disposed within the in-situ Fourier transform infrared spectroscopy detection module. Preferably, the in-situ Fourier transform infrared spectroscopy detection module is an MI-FTIR spectrometer. After sample enrichment, the infrared spectrum of the sample deposited on the cesium iodide cold window is directly acquired within the high-vacuum low-temperature matrix cavity using an FTIR spectrometer, thereby achieving accurate identification and quantitative analysis of the functional group structure of CIs.

[0019] According to an embodiment of the present invention, the system is a system for the generation and detection of atmospheric Kjeldahl intermediates based on laser photolysis-infrared spectroscopy.

[0020] The present invention also provides a method for detecting atmospheric CIs using the above system, comprising the following steps: (1) Adjust the cesium iodide cold window in the high vacuum low temperature matrix cavity of the high vacuum ultra-low temperature reaction cell module so that its surface is perpendicular to the gas outlet of the low pressure flow tube injection module and parallel to the laser outlet of the excimer laser photolysis module. (2) Open the gas inlet valves of the excimer laser photolysis module and the low-pressure flow tube injection module. Mix the three gases, namely diiodoalkane precursor vapor, O2 and dilution carrier gas, through the low-pressure flow tube injection module and deliver them to the high vacuum low temperature matrix cavity of the high vacuum ultra-low temperature reaction cell module. The mixed gas is instantaneously photolyzed by the laser in the path of being sprayed toward the cesium iodide cold window. The generated CH2OO and other products are then deposited on the cesium iodide cold window of the high vacuum ultra-low temperature reaction cell module. (3) After enrichment, rotate the cesium iodide cold window to a position parallel to the optical path of the in-situ Fourier transform infrared spectroscopy detection module and perform in-situ infrared spectroscopy measurement.

[0021] According to an embodiment of the present invention, the detection method further includes step (4): exporting infrared spectral data, identifying and characterizing CIs products based on characteristic absorption peaks, and completing their qualitative analysis.

[0022] According to an embodiment of the present invention, the diiodoalkane precursor vapor is delivered to the low-pressure flow tube injection module through the first inlet by means of inert gas bubbling of the diiodoalkane precursor. O2 is delivered to the low-pressure flow tube injection module via the second air inlet; The diluted carrier gas is delivered to the low-pressure flow tube injection module through the third air inlet.

[0023] According to an embodiment of the present invention, the inert gas and the dilution carrier gas are the same, and for example, can be selected from one of Ar, Ne, Kr, CO2, N2 and Xe.

[0024] According to an embodiment of the present invention, the injection rate ratio of the inert gas to the dilution carrier gas and O2 is 2:(0-5):5.

[0025] In some embodiments, the inert gas inlet rate is 150-250 ml / min, for example 200 ml / min.

[0026] In some embodiments, the O2 injection rate is 375~625 ml / min, for example 500 ml / min.

[0027] In some embodiments, the inlet rate of the dilution carrier gas is 0-625 ml / min, for example 500 ml / min.

[0028] According to an embodiment of the present invention, CH3CHI2 vapor is generated by bubbling diiodoalkane precursors in a diiodoalkane precursor storage module with an inert gas. To maintain a stable CH3CHI2 precursor volatilization rate, the temperature of the diiodoalkane precursor storage module is maintained at 25-35°C, for example, 25°C. According to an embodiment of the present invention, in step (2), the deposition time is 0.5 to 3 hours, for example, 1 hour.

[0029] The beneficial effects of this invention are: This invention proposes a system for the efficient generation and stable capture of reactive intermediates (CIs), high-sensitivity detection, and integrated generation and monitoring. This invention achieves the generation of high concentrations of CIs in a MI-FTIR system through an "in-situ photolysis" mode. This invention effectively "freezes" transient CIs using ultra-low temperature matrix isolation technology, greatly suppressing their decomposition and side reactions, and providing the possibility for studying the atmospheric reaction mechanisms in which they directly participate. This invention utilizes the fingerprint characteristics of FTIR technology to clearly distinguish CIs with different structures and their isomers, overcoming the shortcomings of UV and MS methods. The system of this invention is not only applicable to typical CI systems, but can also be extended to the study of other atmospheric reactive intermediates by changing the precursor reactants, providing strong technical support for fundamental research in atmospheric chemistry. Attached Figure Description

[0030] Figure 1 This is a schematic diagram showing the relationship between the various parts of the system of the present invention.

[0031] Figure 2This is a schematic diagram of the system structure of the present invention; in the figure: 1-flow tube injection module; 101-first gas inlet; 102-second gas inlet; 103-third gas inlet; 104-vacuum gauge; 105-butterfly valve; 2-excimer laser photolysis module; 3-high vacuum ultra-low temperature reaction cell module; 301-high vacuum low temperature matrix cavity; 3011-gas inlet; 3012-cesium iodide cold window; 302-molecular pump group; 303-closed-loop liquid helium cooling system; 4-in-situ Fourier transform infrared spectroscopy detection module; 5-diiodoalkane precursor storage module; 501-inert gas inlet pipe; 502-gas outlet.

[0032] Figure 3 The infrared spectra of CH3CHI2 before and after photolysis to generate the Krüger intermediate CH3CH2OO in Example 2 are shown.

[0033] Figure 4 The infrared spectra of CH3CHI2 before and after photolysis in Comparative Example 1 are obtained as the Krüger intermediate CH3CH2OO. Detailed Implementation

[0034] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0035] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0036] Example 1 Reference Figure 2 A system comprising a low-pressure flow tube injection module 1, an excimer laser photolysis module 2, a high-vacuum ultra-low temperature reaction cell module 3, and an in-situ Fourier transform infrared spectroscopy detection module 4; The low-pressure flow tube injection module 1 is used to mix and deliver the diiodoalkane precursor vapor, O2 and dilution carrier gas to the high-vacuum ultra-low temperature reaction cell module 3. The excimer laser photolysis module 2 serves as the photolysis source and is guided to the high vacuum ultra-low temperature reaction cell module 3 via an optical path; The in-situ Fourier transform infrared spectroscopy detection module 4 is used to acquire and analyze the infrared spectrum of the sample captured on the surface of the cesium iodide cold window 3012 of the high vacuum ultra-low temperature reaction cell module 3.

[0037] The surface of the cesium iodide cold window 3012 of the high vacuum ultra-low temperature reaction cell module 3 is used to capture the sample. The surface of the cesium iodide cold window 3012 of the high vacuum ultra-low temperature reaction cell module 3 is perpendicular to the gas outlet of the low pressure flow tube injection module 1 and parallel to the laser outlet of the excimer laser photolysis module 2.

[0038] Low-pressure flow tube injection module The low-pressure flow tube injection module 1 is equipped with a vacuum gauge 104, a butterfly valve 105, a first air inlet 101, a second air inlet 102 and a third air inlet 103; The first air inlet 101, the second air inlet 102 and the third air inlet 103 are located at one end of the low-pressure flow pipe, and the other end of the low-pressure flow pipe is connected to a butterfly valve and a mechanical pump. The vacuum gauge is positioned in the middle of the low-pressure flow tube; The diiodoalkane precursor is delivered to the low-pressure flow tube injection module 1 via the first inlet 101 through an inert gas bubbling method. O2 is delivered to the low-pressure flow tube injection module 1 via the second air inlet 102; The diluted carrier gas is delivered to the low-pressure flow tube injection module 1 through the third air inlet 103.

[0039] The inner diameter of the low-pressure flow tube injection module 1 is 10~15mm; the length of the low-pressure flow tube injection module 1 is 70-80cm.

[0040] [Diiodoalkane precursor storage module] The system also includes a diiodoalkane precursor storage module 5, which is equipped with an inert gas inlet pipe 501 and an outlet pipe 502. The inert gas inlet pipe 501 extends below the surface of the diiodoalkane precursor liquid.

[0041] High-vacuum ultra-low temperature reaction cell module The high-vacuum cryogenic reaction cell module 3 includes a high-vacuum cryogenic matrix chamber 301, a molecular pump assembly 302, and a closed-loop liquid helium cooling system 303. The gas inlet 3011 of the high-vacuum cryogenic matrix chamber 301 is perpendicular to the cesium iodide cold window 3012. The closed-loop liquid helium cooling system 303 provides a cryogenic and ultra-high vacuum environment for the molecular pump assembly 302.

[0042] The distance between the gas inlet 3011 of the high vacuum low temperature matrix cavity 301 and the cesium iodide cold window 3012 is 1.50-2.0cm.

[0043] The high-vacuum low-temperature matrix cavity 301 is located inside the in-situ Fourier transform infrared spectroscopy detection module 4.

[0044] Example 2 This embodiment uses the photolysis of CH3CHI2 in an excess O2 atmosphere to generate the Krüger intermediate CH3CH2OO as an example to illustrate the specific workflow of the system in Example 1 for CI generation and characterization. The specific method is as follows: Step 1: Reactant Gas Preparation. Place liquid CH3CHI2 into diiodoalkane precursor storage module 5 (bubbling flask) and maintain the flask at a constant temperature of 25°C in a water bath. Connect the gas pipeline, ensuring good airtightness at all interfaces.

[0045] Step 2: System pressure control. Turn on vacuum gauge 104, butterfly valve 105 and mechanical pump, and adjust the pressure inside low-pressure flow tube injection module 1 (inner diameter 12mm, length 75cm) to about 100 Torr, so as to stabilize the reaction gas injection rate and extend the photolysis and enrichment time.

[0046] Step 3: Gas Mixture Introduction. The mixing ratio of Ar, CH3CHI2 vapor, and O2 is precisely controlled using a mass flow meter, and the mixed gas is introduced into the inlet line of the low-pressure flow tube injection module 1. The Ar gas is divided into two streams: one stream enters the bubbling flask and carries out CH3CHI2 vapor (flow rate 200 ml / min) through the first inlet 101 into the low-pressure flow tube injection module 1; the other stream serves as a dilution carrier gas (flow rate 200 ml / min) and enters the low-pressure flow tube injection module 1 through the third inlet 103. O2 is introduced into the low-pressure flow tube injection module 1 through the second inlet 102 at a flow rate of 500 ml / min to reduce the overall concentration of the mixed gas. The bubbling flask is placed in a 25°C water bath to maintain evaporation stability.

[0047] Step 4: Adjust the cesium iodide cold window 3012 inside the high-vacuum cryogenic matrix cavity 301 (vacuum degree is 10). -5 The surface of the gas mixture is aligned with the gas inlet 3011 (the distance between the cesium iodide cold window 3012 and the gas inlet 3011 is controlled at 1.50 cm) and the excimer laser photolysis module 2 (248 nm excimer laser beam). The laser and the gas inlet valve are turned on, so that the mixed gas is instantaneously photolyzed by the laser in the path of the jet towards the cold window. The generated products such as CH2OO are then deposited on the cold window at ~6K. This process lasts for about 1 hour to enrich a sufficient amount of sample.

[0048] Step 5: After enrichment, rotate the cesium iodide cold window 3012 to a position parallel to the optical path of the in-situ Fourier transform infrared spectroscopy detection module 4 (MI-FTIR spectrometer) to perform in-situ infrared spectroscopy measurement.

[0049] Infrared spectral data were exported, and CI products were identified and characterized based on characteristic absorption peaks to complete their qualitative analysis. Results are as follows: Figure 3 As shown, Figure 3In the image (a), the infrared spectrum of the CH3CHI2 / O2 / Ar mixture is shown. Figure 3 Image (b) shows the infrared spectrum of the product obtained by photolysis of a CH3CHI2 / O2 / Ar mixture using a 248 nm laser. The results indicate that after photolysis with a 248 nm laser, the product at 877 cm⁻¹... -1 A new product peak appeared, which is a characteristic peak of CH3CHOO. This indicates that the Krüger intermediate CH3CH2OO was successfully generated after laser photolysis of the CH3CHI2 / O2 / Ar mixture.

[0050] Comparative Example 1 This comparative example, while keeping other experimental conditions consistent, employs a pre-deposition followed by photolysis method to photolyze CH3CHI2 in an excess O2 atmosphere. The specific steps are as follows: Step 1: Reactant Gas Preparation. Place liquid CH3CHI2 into diiodoalkane precursor storage module 5 (bubbling flask) and maintain the flask at a constant temperature of 25°C in a water bath. Connect the gas pipeline, ensuring good airtightness at all interfaces.

[0051] Step 2: System pressure control. Turn on vacuum gauge 104, butterfly valve 105 and mechanical pump, and adjust the pressure inside low-pressure flow tube injection module 1 (inner diameter 12mm, length 75cm) to about 100 Torr, so as to stabilize the reaction gas injection rate and extend the photolysis and enrichment time.

[0052] Step 3: Gas Mixture Introduction. The mixing ratio of Ar, CH3CHI2 vapor, and O2 is precisely controlled using a mass flow meter, and the mixed gas is introduced into the inlet line of the low-pressure flow tube injection module 1. The Ar gas is divided into two streams: one stream enters the bubbling flask and carries out CH3CHI2 vapor (flow rate 200 ml / min) through the first inlet 101 into the low-pressure flow tube injection module 1; the other stream serves as a dilution carrier gas (flow rate 200 ml / min) and enters the low-pressure flow tube injection module 1 through the third inlet 103. O2 is introduced into the low-pressure flow tube injection module 1 through the second inlet 102 at a flow rate of 500 ml / min to reduce the overall concentration of the mixed gas. The bubbling flask is placed in a 25°C water bath to maintain evaporation stability.

[0053] Step 4: Deposit precursor gas onto the cesium iodide cold window 3012, and adjust the cesium iodide cold window 3012 in the high-vacuum low-temperature matrix cavity 301 (vacuum degree is 10). -5 Pa), so that its surface is directly facing the gas inlet 3011 (the distance between the cesium iodide cold window 3012 and the gas inlet 3011 is controlled at 1.50 cm), and the gas inlet valve is opened so that the mixed gas is injected toward the cesium iodide cold window 3012 to begin deposition. This deposition process takes about 1 hour.

[0054] Step 5: Turn on the 248nm excimer laser beam and position it directly on the deposited cesium iodide cold window 3012 surface to begin photolysis. The photolysis duration is approximately 1 hour.

[0055] Step 6: After photolysis is completed, rotate the cesium iodide cold window 3012 to a position parallel to the optical path of the in-situ Fourier transform infrared spectroscopy detection module 4 (MI-FTIR spectrometer) to perform in-situ infrared spectroscopy measurement.

[0056] The infrared spectral data were exported and compared with the infrared spectra obtained in the examples. The results are as follows: Figure 4 As shown, Figure 4 The middle line (a) is the infrared spectrum obtained after depositing a CH3CHI2 / O2 / Ar mixed gas for 1 h. Figure 4 The middle (b) line is the infrared spectrum obtained after photolysis for 1 h. The comparison shows that no obvious new peaks appeared, which indicates that no Krüger intermediate CH3CH2OO was generated after first depositing the CH3CHI2 / O2 / Ar mixed gas and then photolyzing it.

[0057] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system, characterized in that, It includes a low-pressure flow tube injection module, an excimer laser photolysis module, a high-vacuum ultra-low temperature reaction cell module, and an in-situ Fourier transform infrared spectroscopy detection module; The low-pressure flow tube injection module is used to mix and deliver diiodoalkane precursor vapor, O2 and dilution carrier gas to the high-vacuum ultra-low temperature reaction cell module. The excimer laser photolysis module serves as the photolysis source and is guided to the high vacuum ultra-low temperature reaction cell module via an optical path. The in-situ Fourier transform infrared spectroscopy detection module is used to acquire and analyze the infrared spectra of samples captured on the surface of the cesium iodide cold window of the high-vacuum ultra-low temperature reaction cell module.

2. The system as described in claim 1, characterized in that, The cesium iodide cold window surface of the high-vacuum ultra-low temperature reaction cell module is used to capture the sample. The cesium iodide cold window surface of the high-vacuum ultra-low temperature reaction cell module is perpendicular to the gas outlet of the low-pressure flow tube injection module and parallel to the laser outlet of the excimer laser photolysis module.

3. The system as described in claim 1 or 2, characterized in that, The low-pressure flow tube injection module is equipped with a vacuum gauge, a butterfly valve, a first air inlet, a second air inlet, and a third air inlet. The first air inlet, the second air inlet and the third air inlet are located at one end of the low-pressure flow pipe, and the other end of the low-pressure flow pipe is connected to a butterfly valve and a mechanical pump. The vacuum gauge is positioned in the middle of the low-pressure flow tube; The diiodoalkane precursor is delivered to the low-pressure flow tube injection module via the first inlet using an inert gas bubbling method. O2 is delivered to the low-pressure flow tube injection module via the second air inlet; The diluted carrier gas is delivered to the low-pressure flow tube injection module through the third air inlet.

4. The system according to any one of claims 1-3, characterized in that, The inner diameter of the low-pressure flow tube is 10~15mm; the length of the low-pressure flow tube is 70-80cm.

5. The system according to any one of claims 1-4, characterized in that, The system also includes a diiodoalkane precursor storage module, which is equipped with an inert gas inlet pipe and an outlet pipe, with the inert gas inlet pipe extending below the surface of the diiodoalkane precursor liquid.

6. The system according to any one of claims 1-5, characterized in that, The high-vacuum cryogenic reaction cell module includes a high-vacuum cryogenic matrix cavity, a molecular pump assembly, and a closed-loop liquid helium cooling system. The gas inlet of the high-vacuum cryogenic matrix cavity is perpendicular to the cesium iodide cold window, and the closed-loop liquid helium cooling system provides a cryogenic and ultra-high vacuum environment for the molecular pump assembly.

7. The system as described in claim 6, characterized in that, The distance between the gas inlet of the high-vacuum low-temperature matrix cavity and the cesium iodide cold window is 1.50-2.0 cm.

8. The system according to any one of claims 1-7, characterized in that, The high-vacuum low-temperature matrix cavity is located within the in-situ Fourier transform infrared spectroscopy detection module.

9. A method for detecting atmospheric CIs using the system according to any one of claims 1-8, characterized in that, The method includes the following steps: (1) Adjust the cesium iodide cold window in the high vacuum low temperature matrix cavity of the high vacuum ultra-low temperature reaction cell module so that its surface is perpendicular to the gas outlet of the low pressure flow tube injection module and parallel to the laser outlet of the excimer laser photolysis module. (2) Open the gas inlet valves of the excimer laser photolysis module and the low-pressure flow tube injection module. Mix the three gases, namely diiodoalkane precursor vapor, O2 and dilution carrier gas, through the low-pressure flow tube injection module and deliver them to the high vacuum low temperature matrix cavity of the high vacuum ultra-low temperature reaction cell module. The mixed gas is instantaneously photolyzed by the laser in the path of being sprayed toward the cesium iodide cold window. The generated CH2OO and other products are then deposited on the cesium iodide cold window of the high vacuum ultra-low temperature reaction cell module. (3) After enrichment, rotate the cesium iodide cold window to a position parallel to the optical path of the in-situ Fourier transform infrared spectroscopy detection module and perform in-situ infrared spectroscopy measurement.

10. The method as described in claim 9, characterized in that, The diiodoalkane precursor vapor is delivered to the low-pressure flow tube injection module through the first inlet by bubbling the diiodoalkane precursor with inert gas. O2 is delivered to the low-pressure flow tube injection module via the second air inlet; The dilution carrier gas is delivered to the low-pressure flow tube injection module through the third inlet. The injection rate ratio of the inert gas to the dilution carrier gas and O2 is 2:(0-5):5; The inert gas inlet rate is 150~250 ml / min; The O2 injection rate is 375~625 ml / min; The inlet rate of the dilution carrier gas is 0-625 ml / min; And / or, in step (2), the deposition time is 0.5~3h.

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