A method for preparing neutral water molecule clusters

Abstract

The present invention relates to a method for preparing neutral water clusters with a specific size distribution. The instruments and equipment used include: a multifunctional gas distribution system, an Even-Lavie valve, a tunable extreme ultraviolet free electron laser, and a high-resolution reflective time-of-flight mass spectrometer. In the gas distribution system, water vapor, argon, and helium are mixed under heating conditions to form a high-pressure mixed gas. The mixed gas is ejected through a heatable Even-Lavie valve to form a pulsed cluster beam, which is selectively ionized by an extreme ultraviolet free electron laser of a specific wavelength and then detected by a time-of-flight mass spectrometer. According to the test results, by optimizing the gas distribution conditions, the size distribution formed by the Even-Lavie valve can be obtained as (H2O) n , 1≤n≤m, 1≤m≤80 water clusters.

Description

Technical Field

[0001] The invention belongs to the field of neutral cluster preparation and relates to a method for preparing neutral water molecule clusters of specific size. Technical Background

[0002] Water is one of the most ubiquitous substances on Earth and the most important constituent of living organisms. Small water clusters are widely used in chemical engineering, medicine, life sciences, and other fields due to their excellent permeability, high activity, high solubility, and excellent cell affinity. The average water content in the atmosphere is approximately 0.03%, yet it plays a vital role in the atmospheric environment. Natural phenomena such as clouds, fog, rain, frost, and snow are all related to water molecules and are macroscopic manifestations of their phase transitions. Clusters, as the initial state of condensed matter, are the simplest and most effective system for studying the structural composition and structural evolution of water.

[0003] Currently, there are various methods for preparing small molecule water clusters, such as solid-liquid processing techniques, electromagnetic methods, and ultrasonic methods. However, these processes are expensive and difficult to produce molecular beams for microscopic scientific research. While laser sputtering of ice can produce a high-pressure molecular beam of water clusters, maintaining the ice state stable under high vacuum and laser sputtering conditions is technically difficult. Therefore, a simple and easy method for producing neutral water clusters with a specific size distribution is needed.

[0004] The ionization of water clusters is of great significance in numerous fields, including biology, chemistry, and physics. Single-photon threshold ionization is the most effective method for ionizing neutral clusters. The Dalian Coherent Light Source's VUV-FEL, with its continuously tunable wavelength from 50 to 150 nm (8.3 to 24.8 eV), covers the entire ionization energy range of water clusters, making it an ideal light source for detecting water cluster photoionization. Summary of the Invention

[0005] The object of the present invention is to provide a specific size distribution (H2O) n , 1≤n≤m, 1≤m≤80. Required instruments include a multifunctional gas distribution system, a heatable Even-Lavie valve, a tunable extreme ultraviolet free electron laser, and a high-resolution reflectron time-of-flight mass spectrometer.

[0006] The method comprises the following steps:

[0007] 1) Determine the required maximum water cluster size m according to the requirements, 1≤m≤80, m is a positive integer, and determine the required ionization laser wavelength;

[0008] 2) Using gas distribution equipment, controlling the water tank, gas distribution pipeline, gas distribution bottle, gas outlet pipeline, pressure reducing valve and pulse valve, a high-pressure mixed gas with a water concentration ω is prepared in the gas distribution tank under the conditions of room temperature to 60°C, and the molar concentration of water vapor ω ranges from 0.005% to 0.4%; preferably, the selection range of ω is from 0.01% to 0.1%.

[0009] The mixed gas consists of helium, argon and water, and the molar ratio of argon to water is k; the molar ratio k of argon to water ranges from 100≤k≤300; preferably, the k value ranges from 150≤k≤250;

[0010] The total pressure range of the mixed gas is: 4~10MPa; preferably, P 总 The selection range is: 5~6MPa;

[0011] 3) At a selected ionizing light wavelength, using an Even-Lavie pulse valve as a cluster source, measuring the mass spectrum of the mixed gas ejected from the pulse valve outlet at this water vapor concentration, setting the valve back pressure of the pulse valve to be at least 1 MPa lower than the initial total pressure of the mixed gas (i.e., the valve back pressure is less than or equal to the initial total pressure of the mixed gas - 1 MPa); setting the pulse valve pulse width to a range of 25 to 30 μs, and obtaining the maximum size n of the water molecule cluster ejected from the pulse valve outlet under this condition; preferably, the pulse valve pulse width is in the range of 28 to 30 μs;

[0012] 4) comparing the result n obtained in step 3) with the target m;

[0013] a. If the maximum cluster size n detected in the mass spectrum under the initial condition is equal to m, then this condition is the final condition, that is, the gas distribution equipment can output neutral water molecule clusters (H2O) with a maximum size of m and a size distribution of 1 to m. m , the preparation process of neutral water molecule clusters is completed;

[0014] Or b, if n is smaller than the required size m, it is necessary to increase the water vapor concentration and re-prepare the mixed gas; the specific process is to re-prepare the mixed gas with a concentration of aω (1.1≤a≤3) in the gas distribution tank under the conditions described in step 2), and then repeat the detection process of step 3) and the comparison process of step 4); preferably, a is selected in the range of: 1.1≤a≤1.5;

[0015] or c, if n is greater than m, the water vapor concentration needs to be reduced, and the mixed gas needs to be diluted;

[0016] The dilution process is as follows: directly filling helium into the gas distribution cylinder to dilute the water concentration in the mixed gas, or first discharging a part of the mixed gas in the gas distribution cylinder and then filling helium into the gas distribution cylinder to dilute the water concentration in the mixed gas, diluting to b times (0.2 ≤ b < 1, which is the concentration ratio after dilution to that before dilution) of the concentration of the mixed gas in the gas distribution cylinder before dilution, and repeating the detection process of step 3) and the comparison process of step 4). Preferably, the selection range of b is: 0.2 ≤ b ≤ 0.9;

[0017] In the dilution process of step 4)c, if the water concentration in the mixed gas is diluted from X to Y, and then the maximum cluster n detected in the detection process of step 3) is less than m, then after the comparison process of step 4), the process of step 4)b needs to be carried out to re-prepare the mixed gas. The water concentration for re-preparing the gas should be set to X, and the dilution process of step 4)c is repeated within the concentration range of X to Y. Each time, it is diluted to c times of the concentration of the mixed gas in the gas distribution cylinder before the previous dilution, where b < c < 1, and b is the concentration ratio after dilution to that before dilution when the water concentration in the mixed gas is diluted from X to Y.

[0018] The ionization light wavelength range is shown in Table 1.

[0019] The technical solution of the present invention will be further described below with reference to the accompanying drawings. Description of the Drawings

[0020] Figure 1 It shows a schematic diagram of the connection mode of the gas distribution line and related interfaces of the present invention. In the figure, 1 is a piezoresistive vacuum gauge, 2 is a pressure gauge with a range of 2.5 MPa, 3 is a pressure gauge with a range of 16 MPa, 4 is connected to a vacuum pump, 5 is a water tank, 6 is connected to a helium gas cylinder, 7 is connected to an argon gas cylinder, 8 is connected to the inlet of the gas distribution cylinder, 9 is connected to the outlet of the gas distribution cylinder, 10 is a pressure reducing valve, and 11 is connected to an Even-Lavie valve;

[0021] Figure 2 It shows a principle flow chart of the mass spectrometry detection system of the present invention.

[0022] Figure 3 It shows the measured water cluster (H2O) n , and the mass spectrometry diagram with 1 ≤ n ≤ 11.

[0023] Figure 4 It shows the measured water cluster (H2O) n , and the mass spectrometry diagram with 1 ≤ n ≤ 13. Specific Embodiments

[0024] The multifunctional gas distribution device as shown in the attached Figure 1 figure includes: a gas distribution pipeline, a pressure gauge, a piezoresistive vacuum gauge, a gas distribution cylinder, a pressure reducing valve, a water tank, a vacuum pump (Edwards, 6i), and inert gases (helium, argon).

[0025] The gas distribution pipeline is a stainless steel pipeline with an outer diameter of 1 / 4 inch. The helium gas source is a helium cylinder filled with helium, and the argon gas source is an argon cylinder filled with argon.

[0026] The gas distribution cylinder is a sealed bottle with a pressure test rating exceeding 20 MPa and a capacity of 2L. It is equipped with a material inlet and outlet. The material inlet is connected to a helium gas source, an argon gas source, a sealed water tank filled with water, and a vacuum pump via a gas distribution pipeline, through valves. The material outlet is connected to the pulse valve inlet via an outlet pipeline, through a pressure reducing valve, and then to the inlet of the pulse valve.

[0027] Two pressure gauges and a piezoresistive vacuum gauge are installed on the gas distribution pipeline. The ranges of the two pressure gauges are 2.5MPa and 16MPa respectively, and the range of the vacuum gauge is: 1~100kPa.

[0028] The water tank has an outer diameter of 2 inches, a height of 3 inches, an inner diameter of 4 cm, and an inner height of 7 cm. It is used to hold chromatographically pure water samples (HPLC). The water tank is sealed with an oxygen-free copper gasket and then connected to the gas distribution circuit board. The air in the tank also needs to be exhausted.

[0029] The method of removing air from the water tank is as follows: put the water tank filled with an appropriate amount of water (~50mL) into an ethanol (melting point of ethanol is -114.1℃) bath, slowly add liquid nitrogen to the ethanol and stir, stop adding liquid nitrogen when the ethanol becomes viscous or partially solidified, freeze the water tank for 2 minutes, and then use a vacuum pump to extract the gas in the tank through the gas distribution pipeline until the pressure is less than 10 -2 Close the water tank valve. Close the vacuum pump valve to stop pumping, remove the water tank from the ethanol bath, and thaw it before heating and gas distribution.

[0030] Fiberglass cloth is wrapped around the exterior (external surface) of components requiring heating, such as the water tank, gas distribution piping, gas distribution cylinder, gas outlet piping, and pressure reducing valve. Electric heating tape and / or heating wire are installed between the exterior of the heated components and the fiberglass cloth. The heating temperature is controlled by a temperature switch located on the wire connecting the heating tape to the external power source. The piping heating temperature does not exceed 60°C, ensuring the safety of the gas distribution system.

[0031] Before distributing gas, first extract the gas in the gas distribution pipeline, gas outlet pipeline and gas distribution cylinder until the residual pressure is less than 10 -2 After Pa, close the vacuum pump valve.

[0032] Method for preparing water vapor with a concentration of ω: First determine the initial water vapor partial pressure P1 (P1 must be less than the saturated vapor pressure of water at the gas distribution temperature), the argon partial pressure kP1, and the total pressure P 总 (P 总 It must be lower than the upper pressure limit of the gas cylinder);

[0033] The gas distribution sequence is as follows: Open the water tank valve, the vacuum gauge valve, and the gas cylinder inlet valve. After filling the gas cylinder with water vapor P1, close the water tank valve and the vacuum gauge valve, and fill argon to (k + 1)P1 according to the required ratio, and then fill helium to P 总 ; The water vapor concentration can be obtained as ω = P1 / P 总 , and a mixed gas with n(H2O):n(argon) = 1:k can be obtained.

[0034] Gas dilution method: Withdraw part of the mixed gas until the total pressure is bP 总 (0.2 < b < 1), and then fill helium to the target total pressure P 总 ; Or directly fill helium until the total pressure is P 总 / b, and a mixed gas with water vapor concentration ω = bP1 / P 总 , and n(H2O):n(argon) = 1:k can be obtained.

[0035] In the present invention, argon is an auxiliary medium that can cool water cluster ions. The ratio of argon to water vapor should not be too high to avoid the appearance of Ar m + (H2O) n signal and interfering with the test results. The ratio range of argon to water is: 100 ≤ k ≤ 300.

[0036] The cluster source is a heatable Even-Lavie valve (EL-7-4-2008, LAMID-Multidisciplinary Instruments Development, LTD), and the back pressure range is 3 - 6 MPa; the intake air volume (pulse width) range is: 25 - 30 μs.

[0037] Control the water tank, the gas distribution pipeline, the gas cylinder, the outlet pipeline, the pressure reducing valve, and the pulse valve at a certain same fixed temperature from room temperature to 60 °C.

[0038] The mixed gas is ejected through the heatable Even-Lavie valve to form a pulsed cluster beam, which is ionized by an extreme ultraviolet free electron laser with a specific wavelength and then detected by a time-of-flight mass spectrometer.

[0039] The said mass spectrometry detection system is as Figure 2As shown, it includes: a tunable free electron laser (FEL) and a high-resolution reflective time-of-flight mass spectrometer. After the pulse cluster beam passes through the sampling cone (Skimmer, Model 50.8, Size 4.0mm) for sampling, it enters the center of the time-of-flight mass spectrometer accelerator. The molecules in the air flow are ionized by the FEL to form charged ions, and the charged ions are then detected by the high-resolution reflective time-of-flight mass spectrometer. The selected ionization source is a tunable extreme ultraviolet free electron laser with a wavelength tuning range of 50 to 150nm, a pulse width of 1.5ps, a repetition rate of 20Hz, and a single pulse energy of 200μJ. The selected high-resolution reflective time-of-flight mass spectrometer has a gas pressure of less than 10 during injection. -5 Pa, mass spectrometry resolution greater than 10,000.

[0040] Example 1

[0041] Prepare a mixed gas with a water molar concentration of 0.01% and generate water cluster size distribution (H2O) by diluting the water vapor concentration n , the cluster beam with 1≤n≤11, the specific implementation steps are as follows:

[0042] (H2O) listed in Table 1 n , n=1~80 appearance energy and ionizing light wavelength range, determine (H2O) 11 The performance energy is 10.80eV, the available ionizing light wavelength range is: 114.8 ~ 114.5nm, and the actual FEL wavelength used is set to 114.5nm.

[0043] Prepare a gas with a molar concentration of 0.01% H₂O at 5 MPa, where n(argon):n(H₂O) = 175. This corresponds to a water vapor partial pressure of 0.5 kPa. Heat the water tank, gas distribution line, gas distribution bottle, outlet line, and pressure reducing valve to 40°C. Open the valves on the water tank and gas distribution bottle, as well as the piezoresistive vacuum gauge, to allow water vapor to enter the gas distribution bottle. After 10 minutes, when the piezoresistive vacuum gauge reading stabilizes at 4 kPa, close the piezoresistive vacuum gauge valve and the water tank valve. Calculations show that the water vapor needs to be diluted 8-fold to reach the target concentration. First, fill the gas with a fixed ratio of argon to 0.7 MPa. After mixing, partially withdraw the gas to 0.35 MPa, achieving a 2-fold dilution. Then, fill the gas with helium to 0.8 MPa. After mixing, partially withdraw the gas to 0.2 MPa, achieving a total dilution of 8-fold. Fill the gas with sufficient helium to 5 MPa to obtain the target gas.

[0044] The gas in the cylinder is reduced to 4 MPa by a pressure reducing valve and then transferred to the Even-Lavie valve. The valve heating temperature is 40°C, the operating pulse width is 30 μs, and the repetition frequency is 20 Hz. The mass spectrum of the clusters generated by the Even-Lavie valve at this concentration is tested. Figure 3(a) It was found that the maximum cluster size n = 15, which is larger than the required maximum cluster size. Therefore, the mixed gas needs to be diluted at a ratio of 0.8. The method is to extract part of the mixed gas in the gas distribution tank to a total pressure of 4MPa, and then fill it with pure helium to a total pressure of 5MPa. A mixed gas with a water vapor concentration of 0.008% is obtained. The test conditions (valve heating temperature, back pressure, pulse width) are kept unchanged, and the mass spectrum is tested. Figure 3 (b) The maximum cluster size n = 14 was found, which was larger than the required maximum cluster size and required further dilution. Helium was directly added to the gas cylinder to increase the total pressure from 5 MPa to 6 MPa, obtaining a mixed gas with a water vapor concentration of 0.0067%. The mass spectrum was tested. Figure 3 (c) The maximum cluster size n = 12 was found, which was larger than the required maximum cluster size and required dilution. Helium was directly added to the gas cylinder to increase the total pressure from 6 MPa to 8 MPa, obtaining a mixed gas with a water vapor concentration of 0.005%. The mass spectrum was tested. Figure 3 (d) It is found that the maximum cluster size n = 11, and the mass spectrum distribution reaches an ideal state.

[0045] Therefore, it was determined that using the Even-Lavie valve as the cluster source, with a back pressure of 4 MPa, a working pulse width of 30 μs, and a water vapor concentration of 0.005%, it was possible to generate neutral water molecule clusters (H2O) with a maximum size of 11 and a size distribution of 1 to 11. m .

[0046] Example 2

[0047] According to the test results of Example 1, the water cluster size distribution (H2O) is generated. n , cluster beam with 1≤n≤13.

[0048] Under the Even-Lavie valve conditions in Example 1, the mass spectrum of the mixed gas with a water vapor concentration of 0.0067% was tested at an ionization light wavelength of 115.3 nm. Figure 4 (a), the maximum cluster size n = 12, which is smaller than the required size distribution. Combined with the mass spectrum measured at an ionizing light wavelength of 114.5nm, the maximum cluster size obtained under the condition of a water vapor concentration of 0.008% is 14. Therefore, it can be determined that the water cluster size distribution that can be produced is (H2O) n , the mixed gas concentration of the cluster beam with 1≤n≤13 is between 0.0067% and 0.008%.

[0049] The process and conditions are the same as those in Example 1, except that: a gas with a molar concentration of 0.008% H2O and n(argon):n(H2O)=175 is prepared at 5MPa, and the water vapor partial pressure corresponds to 0.4kPa. The water tank, gas distribution pipeline, gas distribution bottle, gas outlet pipeline, and pressure reducing valve are all heated to 40°C. The valves of the water tank and gas distribution bottle, as well as the piezoresistive vacuum gauge, are opened to allow water vapor to enter the gas distribution bottle. After 10 minutes, the piezoresistive vacuum gauge reading is basically stable at 4kPa. The piezoresistive vacuum gauge valve and the water tank valve are closed. Calculation shows that water vapor needs to be diluted 10 times to reach the target concentration. First, fill with argon gas of a fixed ratio to 0.7MPa, mix well, and then extract some of the gas to 0.35MPa, at which point it is diluted 2 times. Then fill with helium to 1MPa, mix well, and then extract some of the gas to 0.2MPa, for a total dilution of 10 times. Fill with sufficient helium to 5MPa to obtain the target gas.

[0050] The target gas has a high water concentration and is diluted at a ratio of 0.9 by extracting part of the mixed gas in the gas distribution tank to a total pressure of 4.5 MPa and then filling it with pure helium to a total pressure of 5 MPa. A mixed gas with a water vapor concentration of 0.0072% is obtained. The mass spectrum is tested at an ionization light wavelength of 115.3 nm using the Even-Lavie valve conditions in Example 1. Figure 4 (b), it is found that the maximum cluster size n = 13, and the mass spectrum distribution reaches an ideal state.

[0051] Therefore, it was determined that when the Even-Lavie valve was used as the cluster source, the back pressure was 4 MPa, the working pulse width was 30 μs, and the water vapor concentration was 0.0072%, the neutral water molecule clusters (H2O) with a maximum size of 13 and a size distribution of 1 to 13 were generated. m .

[0052] Table 1. (H2O) n , n = 1 to 80 appearance energy and ionizing light wavelength range

[0053]

[0054] In the gas distribution system of the present invention, water vapor, argon, and helium are mixed under heating conditions to form a high-pressure mixed gas. The mixed gas is ejected through a heatable Even-Lavie valve to form a pulsed cluster beam. After selective ionization by an extreme ultraviolet free electron laser of a specific wavelength, it is detected by a time-of-flight mass spectrometer. Based on the test results, by optimizing the gas distribution conditions, the size distribution formed by the Even-Lavie valve can be obtained as (H2O) n , 1≤n≤m, 1≤m≤80 water clusters.

Claims

1. A method for preparing neutral water molecule clusters, characterized in that: The gas distribution equipment used includes a gas distribution cylinder, which is a sealed bottle body with a material inlet and a material outlet. The material inlet is connected to a helium gas source, an argon gas source, a water tank filled with water, and a vacuum pump through a gas distribution pipeline through valves. A pressure gauge and a vacuum gauge are provided on the gas distribution pipeline. The material outlet is connected to the pulse valve inlet through an outlet pipeline and a pressure reducing valve. An extreme ultraviolet free electron laser with tunable output wavelength is used as the ionization source of a high-resolution reflectivity time-of-flight mass spectrometer, and the largest neutral water molecule clusters output by the pulse valve are detected by high-resolution reflectivity time-of-flight mass spectrometry. (H2O) n represents a neutral water molecule cluster, n represents the number of water molecules constituting the water molecule cluster, which is called the water cluster size n; Able to form neutral water molecule clusters (H2O) with a size distribution of 1 to n and a maximum size n less than or equal to the required size using a pulse valve n , 1≤n≤80, n is a positive integer; the method comprises the following steps: 1) Determine the required maximum water cluster size m according to the requirements, 1≤m≤80, where m is a positive integer, and determine the required ionization laser wavelength; 2) Using gas distribution equipment, control the water tank, gas distribution pipeline, gas distribution bottle, gas outlet pipeline, pressure reducing valve and pulse valve to prepare a high-pressure mixed gas with a water concentration of w in the gas distribution tank at room temperature ~ 60℃. The molar concentration of water vapor w ranges from 0.005% to 0.4%. The mixed gas consists of helium, argon and water, and the molar ratio of argon to water is k; the range of the molar ratio k of argon to water is: 100≤k≤300, and the total pressure of the mixed gas P 总 The range is: 4~10 MPa; 3) Under the selected ionization wavelength, using an Even-Lavie pulse valve as the cluster source, measure the mass spectrum of the mixed gas ejected from the pulse valve outlet when the water vapor concentration is w. Set the valve back pressure of the pulse valve to be at least 1 MPa lower than the initial total pressure of the mixed gas, that is, the valve back pressure is less than or equal to the initial total pressure of the mixed gas - 1 MPa. Set the pulse valve pulse width to a range of 25-30 μs. Obtain the maximum size n of the water molecule cluster ejected from the pulse valve outlet under this condition. 4) Compare the result n obtained in step 3) with the target m; a. If the maximum cluster size n detected in the mass spectrum under the initial condition is equal to m, then this condition is the final condition, that is, the pulse valve can output neutral water molecule clusters (H2O) with a maximum size of m and a size distribution of 1~m under this gas distribution condition. m , the preparation process of neutral water molecule clusters is completed; Or b. If n is less than the required size m, it is necessary to increase the water vapor concentration and re-prepare the mixed gas. The specific process is to re-prepare the mixed gas with a concentration of aw (where 1.1≤a≤3) in the gas distribution tank under the conditions described in step 2), and then repeat the detection process in step 3) and the comparison process in step 4). or c, if n is greater than m, the water vapor concentration needs to be reduced, and the mixed gas needs to be diluted; The dilution process is as follows: directly filling helium into the gas distribution bottle to dilute the water concentration in the mixed gas, or first discharging part of the mixed gas in the gas distribution bottle and then filling helium into the gas distribution bottle to dilute the water concentration in the mixed gas, diluting it to b times the concentration of the mixed gas in the gas distribution bottle before dilution, where 0.2≤b<1 is the ratio of the concentration after dilution to the concentration before dilution, and repeating the detection process of step 3) and the comparison process of step 4).

2. The preparation method according to claim 1, wherein: The range of water vapor molar concentration w in step 2) is: 0.01% ~ 0.1%, the range of molar ratio k of argon to water is: 150~250, and the total pressure of the mixed gas P 总 The range is: 5~6 MPa, the pulse width of the pulse valve is set in the range of: 28~30μs in step 3), and under the conditions described in step 2), the mixed gas with a concentration of aw, where 1.1≤a≤1.5, is re-prepared in the gas distribution tank and diluted to b times the concentration of the mixed gas in the gas distribution cylinder before dilution, where 0.2≤b≤0.

9.

3. The preparation method according to claim 1, wherein: In the dilution process of step 4)c, if the water concentration in the mixed gas is diluted from X to Y, and the maximum cluster n detected during the detection process of step 3) is less than m, then after the comparison process in step 4), the process of step 4)b needs to be carried out to re-prepare the mixed gas. The water concentration of the re-prepared gas should be set as X, and the dilution process of step 4)c is repeated within the concentration range of X~Y. Each time, it is diluted to c times the concentration of the mixed gas in the gas cylinder before the previous dilution, where b<c<1, and b is the concentration ratio after dilution to before dilution during the process of diluting the water concentration in the mixed gas from X to Y.

4. The preparation method according to claim 1, wherein: The corresponding range of the cluster size n and the ionization light wavelength is: The detected ionization light wavelength range corresponding to n = 1 is 98.2 - 97.9 nm; The detected ionization light wavelength range corresponding to n = 2 is 105.4 - 105.1 nm; The detected ionization light wavelength range corresponding to n = 3 is 111.2 - 110.9 nm; The detected ionization light wavelength range corresponding to n = 4 is 113.3 - 113.0 nm; The detected ionization light wavelength range corresponding to n = 5 is 113.3 - 113.0 nm; The detected ionization light wavelength range corresponding to n = 6 is 113.4 - 113.1 nm; The detected ionization light wavelength range corresponding to n = 7 is 113.6 - 113.3 nm; [[ID=~10]]The detected ionization light wavelength range corresponding to n = 8 is 113.5 - 113.2 nm; The detected ionization light wavelength range corresponding to n = 9 is 114.0 - 113.7 nm; The detected ionization light wavelength range corresponding to n = 10 is 114.3 - 114.0 nm; The detected ionization light wavelength range corresponding to n = 11 is 114.8 - 114.5 nm; The detected ionization light wavelength range corresponding to n = 12 is 115.1 - 114.8 nm; The detected ionization light wavelength range corresponding to n = 13 is 115.3 - 115.0 nm; The detected ionization light wavelength range corresponding to n = 14 is 115.3 - 115.0 nm; The detected ionization light wavelength range corresponding to n = 15 is 115.7 - 115.4 nm; The detected ionization light wavelength range corresponding to n = 16 is 115.4 - 115.1 nm; The detected ionization light wavelength range corresponding to n = 17 is 115.9 - 115.6 nm; The detected ionization light wavelength range corresponding to n = 18 is 116.2 - 115.9 nm; The detected ionization light wavelength range corresponding to n = 19 is 116.3 - 116.0 nm; The detected ionization light wavelength range corresponding to n = 20 is 116.1 - 115.8 nm; The detected ionization light wavelength range corresponding to n = 21 is 116.5 - 116.2 nm; The detected ionization light wavelength range corresponding to n = 22 is 116.6 - 116.3 nm; The detected ionization light wavelength range corresponding to n = 23 is 116.7 - 116.4 nm; The wavelength range of the detected ionizing light corresponding to n = 24 is 116.9-116.6 nm; The wavelength range of the detected ionizing light corresponding to n = 25 is 116.4-116.1 nm; The wavelength range of the detected ionizing light corresponding to n = 26 is 116.5-116.2 nm; The wavelength range of the detected ionizing light corresponding to n = 27 is 116.5-116.2 nm; The wavelength range of the detected ionizing light corresponding to n = 28 is 116.7-116.4 nm; The wavelength range of the detected ionizing light corresponding to n = 29 is 117.0-116.7 nm; The wavelength range of the detected ionizing light corresponding to n = 30 is 117.4-117.1 nm; The wavelength range of the detected ionizing light corresponding to n = 31 is 117.4-117.1 nm; The wavelength range of the detected ionizing light corresponding to n = 32 is 117.4-117.1 nm; The wavelength range of the detected ionizing light corresponding to n = 33 is 117.2-116.9 nm; The wavelength range of the detected ionizing light corresponding to n = 34 is 116.4-116.1 nm; The wavelength range of the detected ionizing light corresponding to n = 35 is 116.6-116.3 nm; The wavelength range of the detected ionizing light corresponding to n = 36 is 116.4-116.1 nm; The wavelength range of the detected ionizing light corresponding to n = 37 is 116.4-116.1 nm; The wavelength range of the detected ionizing light corresponding to n = 38 is 116.5-116.2 nm; The wavelength range of the detected ionizing light corresponding to n = 39 is 117.0-116.7 nm; The wavelength range of the detected ionizing light corresponding to n = 40 is 117.0-116.7 nm; The wavelength range of the detected ionizing light corresponding to n = 41 is 116.7-116.4 nm; The wavelength range of the detected ionizing light corresponding to n = 42 is 116.4-116.1 nm; The wavelength range of the detected ionizing light corresponding to n = 43 is 116.7-116.4 nm; The wavelength range of the detected ionizing light corresponding to n = 44 is 116.9-116.6 nm; The wavelength range of the detected ionizing light corresponding to n = 45 is 116.4-116.1 nm; The wavelength range of the detected ionizing light corresponding to n = 46 is 116.4-116.1 nm; The wavelength range of the detected ionizing light corresponding to n = 47 is 117.0-116.7 nm; The wavelength range of the detected ionizing light corresponding to n = 48 is 116.5-116.2 nm; The wavelength range of the detected ionizing light corresponding to n = 49 is 116.6-116.3 nm; The wavelength range of the detected ionizing light corresponding to n = 50 is 117.0-116.7 nm; The wavelength range of the detected ionizing light corresponding to n = 51 is 116.3-116.0 nm; The wavelength range of the detected ionizing light corresponding to n = 52 is 117.0-116.7 nm; The wavelength range of the detected ionizing light corresponding to n = 53 is 117.4-117.1 nm; The wavelength range of the detected ionizing light corresponding to n = 54 is 117.1-116.8 nm; The wavelength range of the detected ionizing light corresponding to n = 55 is 116.9-116.6 nm; The wavelength range of the detected ionizing light corresponding to n = 56 is 116.0-115.7 nm; The wavelength range of the detected ionizing light corresponding to n = 57 is 116.9-116.6 nm; The wavelength range of the detected ionizing light corresponding to n = 58 is 116.1-115.8 nm; The wavelength range of the detected ionizing light corresponding to n = 59 is 116.7-116.4 nm; The wavelength range of the detected ionizing light corresponding to n = 60 is 116.5-116.2 nm; The wavelength range of the detected ionizing light corresponding to n = 61 is 116.1-115.8 nm; The wavelength range of the detected ionizing light corresponding to n = 62 is 115.7-115.4 nm; The wavelength range of the detected ionizing light corresponding to n = 63 is 115.9-115.6 nm; The wavelength range of the detected ionizing light corresponding to n = 64 is 115.3-115.0 nm; The wavelength range of the detected ionizing light corresponding to n = 65 is 116.4-116.1 nm; The wavelength range of the detected ionizing light corresponding to n = 66 is 115.0-114.7 nm; The wavelength range of the detected ionizing light corresponding to n = 67 is 115.9-115.6 nm; The wavelength range of the detected ionizing light corresponding to n = 68 is 118.1-117.8 nm; The wavelength range of the detected ionizing light corresponding to n = 69 is 117.0-116.7 nm; The wavelength range of the detected ionizing light corresponding to n = 70 is 118.1-117.8 nm; The wavelength range of the detected ionizing light corresponding to n = 71 is 117.0-116.7 nm; The wavelength range of the detected ionizing light corresponding to n = 72 is 119.2-118.9 nm; The wavelength range of the detected ionizing light corresponding to n = 73 is 117.0-116.7 nm; The wavelength range of the detected ionizing light corresponding to n = 74 is 117.0-116.7 nm; The wavelength range of the detected ionizing light corresponding to n = 75 is 117.0-116.7 nm; The wavelength range of the detected ionizing light corresponding to n = 76 is 115.9-115.6 nm; The wavelength range of the detected ionizing light corresponding to n = 77 is 114.8-114.5 nm; The wavelength range of the detected ionizing light corresponding to n = 78 is 114.8-114.5 nm; The wavelength range of the detected ionizing light corresponding to n = 79 is 114.8-114.5 nm; The wavelength range of the detected ionizing light corresponding to n = 80 is 119.2-118.9 nm.

5. The preparation method according to claim 1, wherein: The gas distribution pipeline is a stainless steel pipeline with an outer diameter of 1 / 4 inch. The vacuum gauge is a piezoresistive vacuum gauge with a range of 0.1~100 kPa. The helium gas source is a helium cylinder filled with helium, and the argon gas source is an argon cylinder filled with argon. Glass fiber cloth is wrapped around the outside (outer wall) of components that need to be heated, such as water tanks, gas distribution pipes, gas distribution bottles, gas outlet pipes, and pressure reducing valves. Electric heating belts or electric heating wires are provided between the outside of the heated components and the glass fiber cloth. The pulse valve is a heatable Even-Lavie valve with a back pressure range of 3-6 MPa and an air intake range of 25-30 μs. Control the water tank, gas distribution pipeline, gas distribution bottle, gas outlet pipeline, pressure reducing valve and pulse valve to a same fixed temperature between room temperature and 60℃.

6. The preparation method according to claim 5, characterized in that: The pulse valve is a heatable Even-Lavie valve with a back pressure range of 4-5 MPa and an air intake range of 28-30 μs. Control the water tank, gas distribution pipeline, gas distribution bottle, gas outlet pipeline, pressure reducing valve and pulse valve at the same fixed temperature between 30~40℃.

7. The preparation method according to claim 1, wherein: The laser light source with tunable output wavelength is a tunable extreme ultraviolet free electron laser with a wavelength tuning range of 50~150 nm, a pulse width of 1.5 ps~1 ns, a repetition rate of 20~50 Hz, and a single pulse energy of 20~400 μJ.

8. The preparation method according to claim 7, characterized in that: The laser light source with tunable output wavelength is a tunable extreme ultraviolet free electron laser with a wavelength tuning range of 90~130nm, a pulse width of 1.5~20ps, a repetition frequency of 20~30Hz, and a single pulse energy of 40~200μJ.

9. The preparation method according to claim 1, wherein: High-resolution reflectron time-of-flight mass spectrometry, with an injection pressure of less than 10 -5 Pa, mass spectrometry resolution greater than 10,000.

10. The preparation method according to claim 9, characterized in that: High-resolution reflective time-of-flight mass spectrometry, the injection pressure is less than 8*10 -6 Pa, mass spectrometry resolution greater than 20,000.

11. The preparation method according to claim 1, characterized in that: The water tank must be de-aired before distributing gas. The method of de-airing the water tank is as follows: put the water tank with water smaller than the volume of the water tank into the ethanol bath, add liquid nitrogen to the ethanol and stir, and stop adding liquid nitrogen when the ethanol becomes viscous or partially solidified. After the water tank is frozen for more than two minutes, use a vacuum pump to extract the gas in the water tank through the gas distribution pipeline until the pressure is less than 10 -2 Pa closes the water tank valve; closes the vacuum pump valve to stop pumping, takes the water tank out of the ethanol bath, and then starts heating and gas distribution.

12. The preparation method according to claim 11, characterized in that: Pump until the pressure is less than 8*10 -3 Pa.

13. The preparation method according to claim 1, characterized in that: Before distributing gas, first extract the gas in the gas distribution pipeline, gas outlet pipeline and gas distribution bottle until the residual pressure is less than 10 -2 After Pa, close the vacuum pump valve.

14. The preparation method according to claim 13, characterized in that: Pump until the pressure is less than 8*10 -3 Pa.

15. The preparation method according to claim 1, characterized in that: Method for preparing water vapor with a concentration of ω: First, determine the initial water vapor partial pressure P1, which must be less than the saturated vapor pressure of water at the gas distribution temperature, the argon partial pressure kP1, and the total pressure P 总 , P 总 It must be lower than the upper pressure limit of the gas cylinder; The gas distribution sequence is: open the water tank valve, vacuum gauge valve, and gas bottle inlet valve, fill the gas bottle with water vapor P1, close the water tank valve and vacuum gauge valve, fill the gas bottle with argon to (k+1)P1 according to the required ratio, and then fill it with helium to P 总 ; The water vapor concentration is ω=P1 / P 总 , a mixed gas of n(H2O) : n(argon) = 1 : k.

16. The preparation method according to claim 1, characterized in that: Gas dilution method: Extract a part of the mixed gas until the total pressure is bP 总 , where 0.2 < b < 1, and then fill in helium until the target total pressure P 总 ; or directly fill in helium until the total pressure is P 总 / b, a mixed gas with a water vapor concentration of ω = bP1 / P 总 and n(H2O):n(argon) = 1:k can be obtained.

17. The preparation method according to claim 16, characterized in that: Gas dilution method: extract part of the mixed gas until the total pressure is bP 总 , where b is selected in the range of 0.2~0.9.

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