A method for measuring fluorine atom yield using in-situ chemical fluorescence titration

Abstract

The present invention discloses a method for measuring the fluorine atom yield by in-situ chemical fluorescence titration, which is essentially an improved chemical titration method. This method is particularly applicable to HF chemical lasers. Using H2 that originally exists in the HF chemical laser as the titrant, it makes full use of the original device of the HF chemical laser without the need for additional modification, and has the characteristics of being convenient and easy to use. In addition, the titration indication signal used in this method is the ratio of the NH(A) luminescence intensity to the N2(B) luminescence intensity in the optical cavity in-situ chemical fluorescence. This ratio is only related to the gas flow components in the main gas flow and has nothing to do with the absolute fluorescence intensity. Therefore, it can eliminate the influence of the absolute light intensity fluctuation noise during spectral measurement and can effectively improve the measurement accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of spectral measurement, and in particular relates to a method for measuring the yield of fluorine atoms by in-situ chemical fluorescence titration, which is used to measure the NF in the combustion chamber of a hydrogen fluoride chemical laser. 3 The efficiency of the thermal dissociation of gases to produce fluorine atoms, especially for NF 3 Low pyrolysis efficiency, incomplete dissociation, and the presence of F 2 NF 2 NF 3 In the case of residuals, F 2 NF 2 NF 3 Improve the measurement accuracy by eliminating the interference of residual substances. Background Art

[0002] High-energy gas chemical lasers, represented by hydrogen fluoride chemical lasers, have the advantages of rich laser spectral lines, excellent amplification performance, high energy conversion efficiency, and beam quality close to the diffraction limit. For continuous-wave hydrogen fluoride (HF) chemical lasers, their energy comes from the heat released by the chemical reaction between fluorine atoms and hydrogen molecules (commonly called cold pump reaction), in which excited HF (v) molecules are generated as lasing media:

[0003] F+H 2 →HF(v)+HΔH=-32kcal / mol

[0004] In combustion-driven hydrogen fluoride (HF) chemical lasers, fluorine atoms are usually generated by deuterium gas (D 2 ) and nitrogen trifluoride (NF 3 ) is produced by combustion and pyrolysis in the combustion chamber. During the combustion process, deuterium is completely consumed, while nitrogen trifluoride is in excess. The heat generated by the violent chemical reaction thermally dissociates the excess nitrogen trifluoride to produce the required fluorine atoms. It can be seen that the combustion chamber is one of the most basic and key components of the combustion-driven hydrogen fluoride (HF) chemical laser and its energy source. It can be said that the NF in the combustion chamber is 3 The pyrolysis efficiency directly determines the efficiency upper limit of this type of chemical laser, and determines its characteristic parameters such as scale-up, volume efficiency, and weight efficiency. Therefore, it is necessary to establish a qualitative or quantitative characterization of the combustion chamber NF 3 The method of pyrolysis efficiency is very necessary and can lay the foundation for the combustion chamber optimization research of combustion-driven hydrogen fluoride chemical lasers.

[0005] Currently, in the field of combustion-driven HF chemical lasers, the measurement of NF 3The most commonly used method for pyrolysis efficiency is chemical titration, which uses a titrant gas that can react quickly with fluorine atoms to consume fluorine atoms, injects an indicator gas somewhere downstream, and detects an indicator signal that can reflect the concentration of fluorine atoms. At the titration endpoint, the fluorine atom flow rate is calculated based on the stoichiometric coefficient relationship between the titration gas and fluorine atoms, thereby giving the NF 3 Pyrolysis efficiency.

[0006] However, this chemical titration method has a disadvantage that two groups of injection holes must be set up, the first group is used to inject the titrant, and the second group is used to inject the indicator. Moreover, the two groups of injection holes must be separated by a considerable distance so that the titrant gas flows between the two for a long enough time to ensure that the titrant gas can react thoroughly with the F atoms. Since the combustion-driven HF chemical laser gas flow is in a supersonic flow state, the gas flow speed is very fast, generally 1000-2500 m / s, so it is difficult to ensure sufficient reaction time.

[0007] In view of this, in order to directly utilize the in-situ chemical fluorescence of hydrogen fluoride chemical laser in the optical cavity to 3 To measure the thermal dissociation efficiency, we invented a new method to measure the HF chemical laser NF using in situ chemical fluorescence titration. 3 Method for pyrolysis efficiency. Summary of the invention

[0008] The purpose of the present invention is to provide a method for measuring NF in the main gas flow by in-situ chemical fluorescence titration based on the full use of the original hardware device of HF chemical laser. 3 A facile method for efficient generation of fluorine atoms by thermal dissociation.

[0009] In addition to F atoms, the main gas flow of HF chemical lasers generally contains N 2 or He diluent, and F 2 NF, NF 2 NF 3 When H is injected into the optical cavity 2 When H 2 It undergoes very complex chemical reactions with various species in the main airflow, producing in-situ chemical reaction fluorescence, which contains chemical reaction fluorescence spectra of various wavelengths. 2 The composition of the fluorescence spectrum changes with the different ratios; 2 When the flow rate is large enough, the composition of the fluorescence spectrum is basically the same as H 2 The flow rate has little to do with it, but only with the gas components in the main gas flow. Based on this, the composition of the fluorescence spectrum can be used as a titration indicator signal to measure NF by chemical reaction titration method. 3 Dissociation efficiency.

[0010] Generally speaking, the optical cavity of a hydrogen fluoride chemical laser mainly includes the following chemical reaction steps:

[0011] F+H 2 →HF(v)+H cold pump reaction

[0012] H+F 2 →HF(v)+F heat pump reaction

[0013] The above is a chemical pumping reaction for generating excited state HF(v).

[0014] H+NF 2 →NF(a)+HF

[0015] H+NF(a)→N( 2 D)+HF

[0016] N( 2 D)+NF(a)→N 2 (B)+F produces N 2 (B)

[0017]

[0018] The above is to generate N 2 Chemical reaction of (B) and NH(A).

[0019]

[0020]

[0021] The above is the spontaneous emission fluorescence process.

[0022] Where k is H+N 2 (B), A' is the Einstein spontaneous radiation coefficient of NH(A), and A" is the N 2 (B) Einstein spontaneous radiation coefficient,

[0023] Therefore, NH(A) and N 2 The ratio of the luminous intensity of (B) can be expressed as:

[0024]

[0025] The steady-state approximation for NH(A) is:

[0026]

[0027] Finally, we can get:

[0028]

[0029] That is, NH(A) and N 2 (B) The ratio of luminescence intensity is proportional to the H atom flux.

[0030] According to the fast conversion reaction F+H 2 →HF(v)+H, we can know the H atomic flow rate Equal to titrant H 2 flow As the titration progresses (gradual addition of H 2 ), H atomic flux Finally, when the titration endpoint is reached, the H atom flux Increase to equal the original F atomic flux has reached its maximum value, so NH(A) and N 2 (B) The ratio of luminous intensity also reaches its maximum value. 2 When the titrant flow rate is adjusted, since there are no F atoms, the H atom flow rate remains constant, and NH(A) and N 2 (B) The ratio of luminous intensities also remains constant.

[0031] In summary, it can be concluded that at the titration end point, the titrant H 2 flow Equal to the original F atomic flow The NF in HF chemical laser can be given 3 The F atomic yield from pyrolysis is in is the maximum F atom flux that can be produced theoretically.

[0032] The present invention provides a method for measuring fluorine atom yield by in-situ chemical fluorescence titration, the method comprising the following steps:

[0033] (1) The flow rate into the combustion chamber of the combustion-driven hydrogen fluoride chemical laser is NF 3 Gas and flow rate are D 2 gas, The value range is 5~1500mmol / s. The value range is 5~1500mmol / s, which reduces the NF in the combustion chamber. 3 The mixed gas produced by pyrolysis is sprayed into the optical cavity through a supersonic nozzle;

[0034] (2) Using the formula Calculate the ideal NF 3 Theoretical fluorine atomic flux for complete thermal dissociation

[0035] (3) Using the H at the end of the supersonic nozzle 2 Injection hole, inject H into the mixed gas 2 As a titrant, H 2 It reacts chemically with the atoms and molecules in the mixed gas to produce NH(A), N 2 (B) Molecules in electronically excited states, which produce in situ chemical fluorescence through spontaneous radiative transitions;

[0036] (4) Change H 2 Titrant flow rate Perform n different H 2 Titrant flow rate titration experiment, n is a positive integer greater than or equal to 10, according to The lower limit range is 0.01-0.30, the upper limit range is 1.00-3.00, and the step length is 0.01-0.30. The titration experiment is carried out using a spectrometer to measure different H 2 Titrant flow rate In situ chemical fluorescence spectrum, the luminescence intensity of NH(A) I is read from the spectrum NH(A) and N 2 (B) Luminous intensity Calculate the ratio of the two As the titration indicator signal, different H 2 Titrant flow rate Corresponding information with titration indication signal;

[0037] (5) Ratio As the x-value of the horizontal axis, the ratio As the y-value of the ordinate, plot H 2 Titration curve of titrant flow rate and titration indication signal; As x value, the x values ​​are arranged in order from small to large or from large to small, and the horizontal coordinates of the corresponding data points from 1 to n are marked as x 1 ,x 2 ,x 3 ,…,x n-2 ,x n-1 ,x n ; by ratio As the y value, the ordinate of the corresponding data point from 1 to n is marked as y 1 ,y 2 ,y 3 ,…,y n-2 ,y n-1 ,y n; Subtract the y value from the x value to get the first difference quotient y', subtract the first difference quotient y' from the x value to get the second difference quotient y", and finally find the absolute value of the second difference quotient |y"|. The data point at the maximum absolute value of the second difference quotient |y"| is the turning point of the titration curve. The serial number of this data point is marked as k, and the horizontal axis is marked as x k , the vertical axis is marked as y k ;

[0038] (6) The kth data point corresponding to the turning point of the titration curve is taken as the dividing point, and the first data point to the k-2th data point are taken as the first half of the data points. A linear fit is performed on this part of the data points to obtain a fitting line 1; the k+2th data point to the nth data point are taken as the second half of the data points. A linear fit is performed on this part of the data points to obtain a fitting line 2; the abscissa value of the intersection of the fitting line 1 and the fitting line 2 is the NF of the HF chemical laser. 3 The yield of fluorine atoms produced by pyrolysis.

[0039] When the titration operation is performed, the titration indication signal is the luminescence intensity I of NH(A) in the in-situ chemical fluorescence of the optical cavity. NH(A) and N 2 (B) Luminous intensity The ratio of NH(A) is the electronic excited state of the NH molecule with the labeled energy level A, N 2 (B) is N 2 The labeled energy level of the molecule is the electronic excited state of B.

[0040] NF in the combustion chamber of the present invention 3 The mixed gas produced by pyrolysis contains F, F 2 NF 2 NF 3 A mixed gas of one or more atomic molecules.

[0041] The present invention is a method for measuring NF in a hydrogen fluoride chemical laser combustion chamber. 3 Pyrolysis method for fluorine atom yield.

[0042] When the present invention calculates the first difference quotient, the specific operation method is as follows: Assume that there are n data points in total, and the corresponding data point coordinates are (x 1 ,y 1 ) to (x n ,y n ), for the mth (positive integer) data point in 1 to n, the steps to obtain the first difference quotient y' are: when m = 1, the first difference quotient y' m =(y 2 -y 1 ) / (x 2 -x 1 ), the corresponding data point coordinates are (x1 ,y 1 ); when m = n, the first difference quotient y' m =(y n -y n-1 ) / (x n -x n-1 ), the corresponding data point coordinates are (x n ,y n ); when m is a value between 1 and n other than 1 and n, the first difference quotient y' m =(y m+1 -y m-1 ) / (x m+1 -x m-1 ), the corresponding data point coordinates are (x m ,y m ).

[0043] When the present invention calculates the quadratic difference quotient, the specific operation method is as follows: Assume that there are n data points in total, and the corresponding data point coordinates are (x 1 ,y 1 ) to (x n ,y n ), for the mth data point in 1 to n, the steps to obtain the quadratic difference quotient y" are: when m = 1, the quadratic difference quotient y" m =(y' 2 -y' 1 ) / (x 2 -x 1 ), the corresponding data point coordinates are (x 1 ,y 1 ); when m = n, the quadratic difference quotient y" m =(y' n -y' n-1 ) / (x n -x n-1 ), the corresponding data point coordinates are (x n ,y n ); when m is a value between 1 and n other than 1 and n, the quadratic difference quotient y" m =(y' m+1 -y' m-1 ) / (x m+1 -x m-1 ), the corresponding data point coordinates are (x m ,y m ).

[0044] The beneficial effects of the present invention are:

[0045] 1. Compared with the traditional titration method, the present invention directly uses the in-situ chemical fluorescence of hydrogen fluoride chemical laser cavity to titrate NF 3For measuring the thermal dissociation efficiency, there is no need to set up two groups of injection holes, nor is there a need to ensure that the two groups of injection holes are spaced a considerable distance apart, thereby simplifying the experimental device and making it easier to operate.

[0046] 2. The present invention uses the H that already exists in the hydrogen fluoride chemical laser. 2 As a titrant, the original H 2 The injection hole makes full use of the original hardware device of the hydrogen fluoride chemical laser and does not require additional changes to the hardware, so it is convenient and easy to use.

[0047] 3. The present invention uses the luminescence intensity of NH(A) and N in the cavity in situ chemical fluorescence 2 (B) The ratio of luminescence intensity is used as the titration indicator signal. This ratio is only related to the airflow components in the main airflow and has nothing to do with the absolute fluorescence intensity. Therefore, it can eliminate the noise influence of absolute light intensity fluctuations during spectral measurement and effectively improve the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention, not all embodiments. For ordinary technicians in this field, other drawings can also be obtained based on these drawings without creative work.

[0049] Figure 1 is a flow chart of the present invention;

[0050] Figure 2 The chemical fluorescence spectrum obtained by the experiment of the present invention;

[0051] The horizontal axis is wavelength (nm), and the vertical axis is spectral intensity. Figure 2 NH(A), N 2 (B) The position of the characteristic spectral peaks of the isoluminescent particles;

[0052] Figure 3 It is a spectrum intensity reading result diagram of the titration experiment of the present invention;

[0053] The NH(A) spectrum intensity I is given NH(A) and N 2 (B) Spectral intensity Follow The horizontal axis is The ordinate is the spectral intensity;

[0054] Figure 4 It is a scatter plot of titration data after data processing of the present invention;

[0055] The NH(A) spectrum intensity and N 2 (B) Ratio of spectral intensity Follow The horizontal axis is The ordinate is the spectral intensity ratio

[0056] Figure 5 It is a titration data diagram after data processing of the present invention;

[0057] The NH(A) spectrum intensity and N 2 (B) Ratio of spectral intensity And its quadratic difference quotient and the absolute value of quadratic difference quotient follow The horizontal axis is The ordinate is the spectral intensity ratio as well as The quadratic difference quotient and The absolute value of the quadratic difference quotient. Figure 5 You can see The absolute value of the quadratic difference quotient has a maximum value, and the data point at this point is the turning point of the titration curve;

[0058] Figure 6 The figure is a result of linear fitting (fitting straight line 1) of the data points before the turning point of the titration curve and linear fitting (fitting straight line 2) of the data points after the turning point of the titration curve according to the present invention;

[0059] The horizontal axis is The ordinate is the spectral intensity ratio The horizontal coordinate value of the intersection of fitting line 1 and fitting line 2 is the NF of HF chemical laser 3 The yield of fluorine atoms produced by pyrolysis (equal to 0.42, i.e. 42%). DETAILED DESCRIPTION

[0060] The technical scheme of the present invention will be further described in detail below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described here are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0061] Example

[0062] A method for measuring fluorine atom yield by in-situ chemical fluorescence titration is disclosed, and the method is applied to a HF chemical laser system.

[0063] Figure 1 The present invention provides a method for measuring HF chemical laser NF by in-situ chemical fluorescence titration.3 Specific flow chart of the method for thermal dissociation efficiency. This embodiment includes the following specific steps:

[0064] (1) NF is introduced into the combustion chamber of the combustion-driven hydrogen fluoride chemical laser. 3 Gas (flow rate is and D 2 Gas (flow rate is ), and N with a flow rate of 8.0 mmol / s was also introduced. 2 Dilution gas, excess NF in the combustion chamber 3 The pyrolysis products contain F, F 2 NF 2 NF 3 A mixed gas of various atomic molecules is sprayed into the optical cavity through a supersonic nozzle.

[0065] (2) Using the formula Calculate the ideal NF 3 Theoretical fluorine atomic flux for complete thermal dissociation

[0066] (3) Using the H at the end of the supersonic nozzle 2 The injection hole is used to inject a flow rate of F into the mixed gas containing F atoms. H 2 As a titrant, H 2 It reacts chemically with various atoms and molecules in the mixed gas to produce NH(A), N 2 (B) Electronic excited state species, which produce in situ chemical fluorescence through spontaneous radiative transitions.

[0067] (4) Change H 2 Titrant flow rate Several titration experiments were performed, a total of 12 experiments were conducted. 2 Titrant flow rate It is difficult to control precisely, so each experiment The values ​​are not equally spaced. In the 12 experiments, The values ​​are: 0.06, 0.17, 0.26, 0.33, 0.40, 0.43, 0.50, 0.58, 0.64, 0.80, 1.04, and 1.28 respectively.

[0068] Using PIXIS spectrometer to measure different hydrogen flow rates In situ chemical fluorescence spectrum of the optical cavity under conditions, typical fluorescence spectrum such as Figure 2 shown.

[0069] (5) Read the luminescence intensity I of NH(A) from the spectrum measured in each experiment NH(A) and N2 (B) Luminous intensity Calculate the ratio of the two As titration indicator signal; give different hydrogen flow conditions The results are shown in the following table.

[0070]

[0071] By ratio As the horizontal axis, the luminous intensity of NH(A) I NH(A) and N 2 (B) Luminous intensity As the ordinate, plot the spectral intensity trend as Figure 3 shown.

[0072] By ratio As the x-value of the horizontal axis, the ratio As the y-value of the ordinate, draw the titration curve as Figure 4 As shown. Figure 4 It can be clearly seen that both the first and second half of the titration curve show good linear distribution characteristics.

[0073] (6) Find the turning point of the titration curve.

[0074] By ratio As x value, arrange the x values ​​in ascending order, and mark the horizontal coordinates of the corresponding points from 1 to 12 as x. 1 ,x 2 ,x 3 ,…,x 10 ,x 11 ,x 12 ; by ratio As the y value, the ordinates of the corresponding points from 1 to 12 are marked as y 1 ,y 2 ,y3,…,y10,y 11 ,y 12 ; Take the difference quotient of the y value and the x value to get the difference quotient y', marked as y' 1 ,y' 2 ,y' 3 ,…,y' 10 ,y' 11 ,y' 12 ; Take the first difference quotient y' and make a difference quotient of x to get the second difference quotient y", marked as y" 1 ,y” 2 ,y” 3 ,…,y” 10 ,y” 11 ,y” 12 ; Finally, find the absolute value of the quadratic difference quotient |y”|, marked as |y'1 |,|y' 2 |,|y' 3 |,…,|y' 10 |,|y' 11 |,|y' 12 |.

[0075] When calculating the first difference quotient, the specific operation method is as follows: In this embodiment, there are n=12 data points in total. For the mth data point, the first difference quotient y' is obtained. m The steps are: when m = 1, the first difference quotient y' m =(y 2 -y 1 ) / (x 2 -x 1 ), the corresponding data point coordinates are (x 1 ,y 1 ); when m = 12, the first difference quotient y' m =(y 12 -y 11 ) / (x 12 -x 11 ), the corresponding data point coordinates are (x 12 ,y 12 ); when m is a value between 1 and n other than 1 and n, the first difference quotient y' m =(y m+1 -y m-1 ) / (x m+1 -x m-1 ), the corresponding data point coordinates are (x m ,y m ).

[0076] When calculating the quadratic difference quotient, the specific operation method is as follows: In this embodiment, there are n=12 data points in total. For the mth data point, the quadratic difference quotient y" is obtained. m The steps are: when m = 1, the quadratic difference quotient y" m =(y' 2 -y′ 1 ) / (x 2 -x 1 ), the corresponding data point coordinates are (x 1 ,y 1 ); when m = 12, the quadratic difference quotient y" m =(y' 12 -y' 11 ) / (x 12 -x 11 ), the corresponding data point coordinates are (x 12 ,y 12 ); when m is a value between 1 and n other than 1 and n, the quadratic difference quotient y" m=(y' m+1 -y' m-1 ) / (x m+1 -x m-1 ), the corresponding data point coordinates are (x m ,y m ).

[0077] Next, the absolute value of the quadratic difference quotient y" is calculated to obtain |y"|.

[0078] The final summary results are shown in the following table.

[0079]

[0080] By ratio As the horizontal axis, the ratio The quadratic difference quotient and the absolute value of the quadratic difference quotient are used as the ordinates to draw a curve such as Figure 5 As shown in the figure, the position where the absolute value of the quadratic difference quotient |y”| is the largest is the turning point of the titration curve.

[0081] from Figure 5 It can be seen that the fifth data point (x 5 ,y 5 ) corresponds to the absolute value of the quadratic difference quotient |y”| maximum (|y” 5 |=14.57), so the fifth data point (x 5 ,y 5 ) is the turning point of the titration curve.

[0082] (7) Obtaining NF of HF chemical laser 3 The yield of fluorine atoms produced by pyrolysis.

[0083] like Figure 6 As shown, according to the titration turning point k = 5, the fifth data point (x 5 ,y 5 ) as the dividing point, take the 1st data point to the 3rd data point (5-2=3) as the first half of the data points, perform linear fitting on this part of the data points, and get fitting line 1; take the 7th data point (5+2=7) to the 12th data point as the second half of the data points, perform linear fitting on this part of the data points, and get fitting line 2.

[0084] The horizontal coordinate value of the intersection of fitting line 1 and fitting line 2 is the NF of HF chemical laser 3 The yield of fluorine atoms produced by thermal decomposition. Figure 6 It can be seen that the abscissa at the end point of the titration is 0.42, so it can be concluded that the NF of the HF chemical laser is 3 The yield of fluorine atoms produced by thermal decomposition is 42%.

[0085] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A method for measuring fluorine atom yield using in-situ chemical fluorescence titration, characterized in that: The method comprises the following steps: (1) The flow rate of hydrogen fluoride chemical laser into the combustion chamber is The NF3 gas and flow rate are of D2 gas, The value range is 5~1500mmol / s. The value range is 5 to 1500mmol / s, and the mixed gas produced by the pyrolysis of NF3 in the combustion chamber is sprayed into the optical cavity through a supersonic nozzle; (2) Using the formula Calculate the theoretical fluorine atomic flow rate for complete thermal dissociation of NF3 under ideal conditions (3) Using the H2 injection hole at the end of the supersonic nozzle, H2 is introduced into the mixed gas as a titrant. H2 reacts chemically with the atoms and molecules in the mixed gas to produce electronic excited state molecules such as NH(A) and N2(B). These excited state molecules produce in-situ chemical fluorescence through spontaneous radiation transitions. (4) Change the H2 titrant flow rate Perform n times with different H2 titrant flow rates titration experiment, n is a positive integer greater than or equal to 10, according to The lower limit range is 0.01-0.30, the upper limit range is 1.00-3.00, and the step length is 0.01-0.

30. The titration experiment is carried out and the spectrometer is used to measure different H2 titrant flow rates. In situ chemical fluorescence spectrum, the luminescence intensity of NH(A) I is read from the spectrum NH(A) and N2(B) luminescence intensity Calculate the ratio of the two As the titration indicator signal, the titration results of n experiments under different H2 titrant flow rates are obtained. Corresponding information with titration indication signal; (5) Ratio As the x-value of the horizontal axis, the ratio As the y-value of the ordinate, draw the titration curve of H2 titrant flow rate and titration indicator signal; As x values, the x values ​​are arranged in order from small to large or from large to small, and the horizontal coordinates of the corresponding data points from 1 to n are marked as x1, x2, x3, ..., x n-2 ,x n-1 ,x n ; by ratio As y values, the ordinates of the corresponding data points from 1 to n are marked as y1, y2, y3, …, y n-2 ,y n-1 ,y n ; Subtract the y value from the x value to get the first difference quotient y', subtract the first difference quotient y' from the x value to get the second difference quotient y", and finally find the absolute value of the second difference quotient |y"|. The data point at the maximum absolute value of the second difference quotient |y"| is the turning point of the titration curve. The serial number of this data point is marked as k, and the horizontal axis is marked as x k , the vertical axis is marked as y k ; (6) taking the kth data point corresponding to the turning point of the titration curve as the dividing point, taking the first data point to the k-2th data point as the first half of the data points, performing linear fitting on this part of the data points, and obtaining a fitting straight line 1; The k+2th data point to the nth data point are taken as the second half of the data points, and a linear fit is performed on this part of the data points to obtain a fitting straight line 2; the abscissa value of the intersection of the fitting straight line 1 and the fitting straight line 2 is the yield of fluorine atoms produced by the NF3 thermal decomposition of the HF chemical laser.

2. The method according to claim 1, characterized in that: Where NH(A) is the electronic excited state of the NH molecule with the labeled energy level A, and N2(B) is the electronic excited state of the N2 molecule with the labeled energy level B; the titration indicator signal is the luminescence intensity I of NH(A) in the cavity in situ chemical fluorescence. NH(A) and N2(B) luminescence intensity ratio.

3. The method according to claim 1, characterized in that: There are n data points in total, and the corresponding data point coordinates are from (x1, y1) to (x n ,y n ), for the mth (positive integer) data point in 1 to n, the steps to obtain the first difference quotient y' are: when m = 1, the first difference quotient y' m =(y2-y1) / (x2-x1), the corresponding data point coordinates are (x1, y1); when m=n, the first difference quotient y' m =(y n -y n-1 ) / (x n -x n-1 ), the corresponding data point coordinates are (x n ,y n ); when m is a value between 1 and n other than 1 and n, the first difference quotient y' m =(y m+1 -y m-1 ) / (x m+1 -x m-1 ), the corresponding data point coordinates are (x m ,y m ).

4. The method according to claim 1 or 3, characterized in that: There are n data points in total, and the corresponding data point coordinates are from (x1, y1) to (x n ,y n ), for the mth data point in 1 to n, the steps to obtain the quadratic difference quotient y" are: when m = 1, the quadratic difference quotient y" m =(y'2-y'1) / (x2-x1), the corresponding data point coordinates are (x1, y1); when m=n, the quadratic difference quotient y" m =(y' n -y' n-1 ) / (x n -x n-1 ), the corresponding data point coordinates are (x n ,y n ); when m is a value between 1 and n other than 1 and n, the quadratic difference quotient y" m =(y' m+1 -y' m-1 ) / (x m+1 -x m-1 ), the corresponding data point coordinates are (x m ,y m ).

5. The method according to claim 1, characterized in that: The mixed gas generated by the pyrolysis of NF3 in the combustion chamber is a mixed gas containing one or more atomic molecules of F, F2, NF2, NF3, etc.

6. The method according to claim 1, characterized in that: It is a method for measuring the fluorine atom yield from the pyrolysis of NF3 in a hydrogen fluoride chemical laser combustion chamber.

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