Method and apparatus for measuring the temperature of gas molecules

Abstract

This invention provides a temperature calculation method that can accurately measure the temperature of multiple types of gas molecules. [Solution] A method for measuring the temperature of gas molecules, The absorbance spectrum of the gas molecules to be measured is obtained, Absorbance A used in temperature estimation of gas molecules by RDT method max For the equation, β(NL,T,μ ν To minimize the contribution of ), we integrate both sides with respect to the wavenumber, and then transform the above equation to express the integrated absorbance α0, and take the natural logarithm of both sides to obtain equation (eq2): This is a method for measuring the temperature of a gas molecule, in which a linear fitting using the rotational quantum number J is applied to the integrated absorbance α0 based on JPEG2026088956000025.jpg21150 to estimate the thermodynamic temperature T of the gas molecule being measured.

Description

[Technical Field]

[0001] This invention relates to a temperature measurement method and a temperature measurement apparatus for calculating the temperature of a gas molecule from the absorbance spectrum of the gas molecule. [Background technology]

[0002] Dual-comb spectroscopy has been proposed as a method to measure how much of the spectral components of light are absorbed by a substance under test with high resolution and in a short time. Dual-comb spectroscopy is a method that measures the absorption lines (absorption spectrum) of a substance under test by detecting the beats (beats) generated by the interference of two optical frequency combs, which are synchronized and oscillated by two optical comb light sources with slightly different oscillation frequencies.

[0003] Non-patent document 1 describes the measurement of gas molecule temperature based on measurements using dual-comb spectroscopy.

[0004] Furthermore, in recent years, a method called rotational-state distribution thermometry (RDT method) has been proposed, which uses dual-comb spectroscopy to measure the temperature of gas molecules based on the fact that the vibrational rotation spectrum of gas molecules is a function of temperature (Non-Patent Literature 2). Non-Patent Literature 2 shows that appropriate temperature measurement results were obtained for acetylene gas. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Sho Okubo, Kana Iwakuni, Koichi MT Yamada, Hajime Inaba, Atsushi Onae, Feng-Lei Hong, Hiroyuki Sasada, “Transition dipole-moment of the m1 t m3 band of acetylene measured with dual-comb Fourier-transform spectroscopy”, Journal of Molecular Spectroscopy 341 (2017) 10-16, 6 September 2017 [Non-Patent Document 2] Yukiko Shimizu1, Sho Okubo1, Atsushi Onae, Koichi MT Yamada, Hajime Inaba, “Molecular gas thermometry on acetylene using dual-combspectroscopy: analysis of rotational energy distribution”, Applied Physics B (2018) 124:71, 4 April 2018 [Overview of the project] [Problems that the invention aims to solve]

[0006] The RDT method described in Non-Patent Document 2 is considered an effective measurement method for measuring the temperature of acetylene gas. However, there is a need for a temperature calculation method and temperature measurement device that can accurately measure the temperature of multiple types of gas molecules. [Means for solving the problem]

[0007] According to one aspect of the present invention, a method for measuring the temperature of gas molecules, The absorbance spectrum of the gas molecules to be measured is obtained, Absorbance A used in temperature estimation of gas molecules by RDT method max The equation: [Number] Here, β(NL, T, μ ν ) is a proportionality constant, h is Planck's constant c is the speed of light in vacuum, B tilde is the rotational constant, k B is the Boltzmann constant, T is the thermodynamic temperature, J is the rotational quantum number, m is the number (index number) of the energy levels of the molecule, g I is the spin multiplicity, F(m) is a correction term, Regarding β(NL, T, μ ν ) to reduce its contribution, both sides of the above equation are integrated with respect to wavenumber, and the above equation is transformed into an equation (eq1) representing the integrated absorbance α0: [Number] Here, A(ν tilde) is the absorbance spectrum of the gas molecule to be measured, The equation (eq2) obtained by transforming both sides and taking the natural logarithm: [Number] <00000​​​​​​​​​​​​​​​​​These and other objects, features, and advantages of the present invention will become even clearer from the detailed description of typical embodiments of the present invention shown in the accompanying drawings. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows an example configuration of a measurement system for measuring the absorption spectrum of a gas using the dual-comb spectroscopy method according to this embodiment. [Figure 2] This diagram shows the interference wave and the absorption characteristics obtained from that interference wave. [Figure 3] This is a diagram showing the absorbance spectrum. [Figure 4] This graph shows the analysis results for acetylene gas using the RDT method. [Figure 5] This figure shows the results of fitting hydrogen cyanide gas using the RDT method. [Figure 6] This graph shows the analysis results for acetylene gas using the ILRDT method according to this embodiment. [Figure 7] This graph shows the absorbance spectrum of hydrogen cyanide. [Figure 8] This figure shows the analysis results for hydrogen cyanide using the ILRDT method according to this embodiment. [Figure 9] This graph shows the absorbance spectrum of carbon monoxide. [Figure 10] This figure shows the analysis results for carbon monoxide using the ILRDT method according to this embodiment. [Figure 11] This is a graph showing the absorbance spectrum of carbon dioxide. [Figure 12] This figure shows the analysis results for carbon dioxide using the ILRDT method according to this embodiment. [Figure 13] This graph shows the absorbance spectrum of hydrogen chloride. [Figure 14] This figure shows the analysis results for hydrogen chloride using the ILRDT method according to this embodiment. [Figure 15]This is a flowchart illustrating the temperature measurement process according to this embodiment. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described with reference to the drawings. In the drawings, similar components or functional parts are given the same reference numerals. For ease of understanding, the scale of these drawings has been appropriately changed. Furthermore, the embodiments shown in the drawings are just one example of how to carry out the present invention, and the present invention is not limited to the illustrated embodiments.

[0013] The following describes the method and apparatus for calculating the temperature of gas molecules according to this embodiment. The temperature calculation method according to this embodiment relates to rotational thermometry (RDT method) which measures the temperature of gas molecules using dual-comb spectroscopy. As will be described in detail below, the temperature calculation method according to this embodiment enables accurate temperature measurement of various types of gas molecules.

[0014] Figure 1 shows an example of the configuration of a measurement system for measuring the absorption spectrum of a gas using the dual-comb spectroscopy method according to this embodiment. In the measurement system 300, the signal optical comb 11 and local optical comb 12 (dual-comb laser) generated by the dual-comb generator 10 are amplified via erbium-doped fiber amplifiers (EDFAs) 21 and 22, respectively, combined by a polarizing beam splitter (PBS) 23, and transmitted through the gas cell 24 of the substance to be measured.

[0015] The synthesized dual-comb laser passes through the gas cell 24, then through the band-pass filter (BPF) 25, is split by the PBS 26, and is received by the balanced photodetector (BPD) 27. The dual-comb laser is photoelectrically converted by the BPD 27, and its signal is amplified by the low-noise amplifier (LNA) 28 and sampled as an interfering mass (IGM) by the digitizer 30 at a sampling frequency of, for example, 100 MHz. The personal computer (PC) 40 performs data processing of the acquired interfering mass (IGM). As an example, Δf rep The frequency is 844Hz, and the bandpass filter 25 has a center wavelength of 1550nm and a bandwidth of 12nm. As the dual-comb generator 10 in the measurement system 300, a small, simple, and low-cost dual-comb fiber laser with shared mechanism may be used, as it does not require a complex control system.

[0016] By using the measurement system 300, the PC 40 can acquire an interfering wave (IGM) 81 as shown in Figure 2, and by performing data processing (integration averaging of the interfering wave, fast Fourier transform, etc.), the absorption spectrum 82 of the substance to be measured can be measured. Here, the PC 40 may acquire the absorption spectrum of the substance to be measured using a measurement method known in this field, which is dual-comb spectroscopy. In the measurement system 300, the digitizer 30 and the PC 40 function as a temperature measuring device 200 that performs a method for measuring the temperature of gas molecules.

[0017] The principle of the gas molecule temperature measurement method according to this embodiment will be explained below.

[0018] According to Lambert-Beer's Law, transmittance is expressed by the following formula:

[0019]

number

[0020] Here, I(ν tilde) is the intensity of transmitted light, I0(ν tilde) is the intensity of incident light, α(ν tilde) is the absorption coefficient (unit [cm^-1]) (a constant specific to the substance) consisting of the concentration c (unit [molecule / cm^3]) of the substance and the absorption cross-section σ (unit [cm^2 / molecule]), and L is the distance the light travels. The absorption coefficient α(ν tilde) indicates how much light a gas molecule absorbs, but it depends on the spatial distribution and motion of the molecules. In other words, it depends on the spectral shape and width of the absorption line.

[0021] To describe this spectral shape, we use the shape function V(ν-tilde). The shape function V(ν-tilde) is a function that describes the distribution (position) and motion (velocity) of gas molecules in space, describing how molecules move randomly and with what probability they move in different directions. Therefore, the absorption coefficient α(ν-tilde) is expressed by the following equation.

[0022]

number

[0023] Here, α0 is the maximum absorption coefficient.

[0024] Rewriting the Lambert-Beer law using the shape function V(ν-tilde) yields the following:

[0025]

number

[0026] The shape function V(ν-tilde) is a function like the Voigt function (a function that combines the Gaussian distribution considering the Doppler spreading of gas molecules with the Lorentz distribution due to pressure spreading), and it needs to be normalized by area. Therefore, the following equation (2) holds.

[0027]

number

[0028] Here, the absorbance A(ν tilde) (absorbance spectrum) is a quantity indicating how much a substance absorbs light and is defined by the following equation.

[0029]

Equation

[0030] Therefore, from Lambert-Beer's law, the absorbance spectrum is represented by the following equation (3).

[0031]

Equation

[0032] By integrating Equation (3) with respect to the wavenumber ν tilde, the following Equation (4) is obtained.

[0033]

Equation

[0034] Here, α0 represents the integrated absorbance, and as shown in Figure 3, it is a quantity representing the total area (indicated by symbol 92) of the absorbance distribution (indicated by symbol 91) at the absorption line (peak value A max indicated by symbol 93). The above discussion is made in Non-Patent Document 1.

[0035] Here, as described in Non-Patent Document 2, since the shape of the absorbance spectrum A(ν tilde) follows the Boltzmann distribution, the absorbance A max expressed as a function of the molecular energy level number m (index number) gives the following equation.

[0036]

Equation

[0037] Here, β(NL,T,μ ν) is the proportionality constant, h is Planck's constant, c is the speed of light in a vacuum, B tilde is the rotational constant, k B is the Boltzmann constant, T is the thermodynamic temperature, J is the rotational quantum number, m is the energy level number (index number) of the molecule, g I is the spin multiplicity, and F(m) is the correction term.

[0038] The method of calculating temperature T from the shape of the absorbance spectrum using this equation (5) is called the RDT (Rotational-state Distribution Thermometry) method, and the measurement of acetylene gas temperature using the RDT method is demonstrated in Non-Patent Document 2.

[0039] Figure 4 shows the results of dual-comb spectroscopy using the measurement system 300 for acetylene gas. 12 The absorption spectrum of C2H2 was measured, and the temperature was estimated by the RDT method, i.e., absorbance A max The results of temperature estimation performed by fitting with J as the adjustment parameter are shown. Here, based on equation (5), A max This utilizes the following relationship between the right-hand and left-hand sides.

[0040]

number

[0041] In this case, the temperature estimation result for acetylene gas using the RDT method was 23.0°C, which, when compared to the reference temperature of 22.5±0.5°C obtained by temperature sensors, indicates that an accurate temperature estimation result was obtained.

[0042] However, when the temperature was calculated using the RDT method in relation to the absorbance of hydrogen cyanide gas (HCN), absorbance A maxIt was found that the fitting was unsuccessful, making analysis impossible. Figure 5 shows the results of fitting based on the RDT method to the absorbance of hydrogen cyanide gas (HCN). As shown in Figure 5, it can be seen that profiles 111 and 112 obtained by the RDT method cannot be correctly fitted to the absorbance shown by the black circle plots (R branch) and black square plots (P branch) in the graph.

[0043] The inventors believe that the cause of this is β(NL,T,μ) in equation (5) based on the Boltzmann distribution. ν It was estimated that ) was having an influence.

[0044] Therefore, β(NL,T,μ ν To reduce the contribution of ), we integrate both sides of equation (5) with respect to the wave number to obtain the following equation (6).

[0045]

number

[0046] Furthermore, by transforming equation (6) using equation (4) and taking the natural logarithm of both sides, we obtain the following equation (7).

[0047]

number

[0048] In the temperature measurement method according to this embodiment, in order to simplify temperature determination, the contribution of F(m) (Herman-Wallis Factor) is assumed to be small, and equation (7) is set as follows.

[0049]

number

[0050] As described above, in the temperature measurement method according to this embodiment, a term based on the rotational quantum number J and β(NL,T,μ νThe format was designed to separate the integral absorbance α0 from the rotational quantum number J. In this temperature measurement method, it is possible to estimate the temperature T with respect to the integral absorbance α0 by linear fitting using the rotational quantum number J. When applying the fitting, m, h, c, k B , g I β can be treated as a constant. When performing fitting based on equation (7) or (8), the second term on the right-hand side (β(NL,T,μ) ν The term ) can be ignored as its contribution is small.

[0051] The temperature measurement method using equation (7) or equation (8) according to this embodiment shall also be called the ILRDT method, in the sense that it is an RDT method that incorporates integration and logarithmization.

[0052] The following shows the analysis results of temperature calculations for various gas molecules using the ILRDT method (linear fitting based on equation (8)). Here, temperature estimation was performed on infrared absorption spectra due to vibrational-rotational transitions of molecules obtained from the HITRAN database. Since the HITRAN database allows data acquisition by specifying a temperature, the estimated values ​​are compared below using the acquired temperature as the reference temperature.

[0053] Figure 6 is a graph showing the analysis results for acetylene gas. In the graphs on the left and right of Figure 6, the vertical axis represents absorbance ln(α0 / |m|) and the horizontal axis represents J(J+1). In the graph on the left of Figure 6, lines 121 and 122 show the results of linear fitting based on equation (8) to the absorbances of the R branch (m: odd) and R branch (m: even), respectively. In the graph on the right of Figure 6, lines 123 and 124 show the results of linear fitting based on equation (8) to the absorbances of the P branch (m: odd) and P branch (m: even), respectively. From Figure 6, it can be seen that the linear fitting based on equation (8) to the absorbance of acetylene gas has been correctly performed.

[0054] Based on the analysis using equation (8) above, the estimated temperature for acetylene gas was 295.75 K, which is close to the reference temperature of 296 K according to the HITRAN database.

[0055] Next, the analysis results for hydrogen cyanide (HCN) based on equation (8) will be explained with reference to Figures 7 and 8. Figure 7 shows the absorbance spectrum (indicated by 170) of hydrogen cyanide (HCN). In Figure 7, the vertical axis represents absorbance and the horizontal axis represents wavelength (the same applies to Figures 9, 11, and 13 below). Hydrogen cyanide (HCN) has an absorption band in the 1.5 μm wavelength range. Figure 8 is a graph showing the analysis results for hydrogen cyanide (HCN). In the graphs shown on the left and right of Figure 8, the vertical axis represents absorbance ln(α0 / |m|) and the horizontal axis represents J(J+1) (the same applies to Figures 10, 12, and 14 below). In the graph on the left of Figure 8, line 171 shows the result of linear fitting based on equation (8) to the absorbance of the R branch, and in the graph on the right of Figure 8, line 172 shows the result of linear fitting based on equation (8) to the absorbance of the P branch. Figure 8 shows that the linear fitting based on equation (8) for the absorbance of hydrogen cyanide (HCN) is performed correctly.

[0056] Based on the analysis using equation (8) above, the estimated temperature T for hydrogen cyanide (HCN) was 296.8K, which is close to the reference temperature of 296K according to the HITRAN database.

[0057] Thus, the analysis based on equation (8) (analysis by ILRDT method) is effective not only for acetylene gas but also for hydrogen cyanide gas.

[0058] Below, we present the results of analyses for carbon monoxide (CO), carbon dioxide (CO2), and hydrogen chloride (HCl) as an example demonstrating that the estimation of temperature T by linear fitting based on equation (8) is also effective for multiple types of gases (multi-gas).

[0059] The results of the analysis of carbon monoxide (CO) based on equation (8) will be explained with reference to Figures 9 and 10. Figure 9 shows the absorbance spectrum of carbon monoxide (indicated by 140). Carbon monoxide (CO) has an absorption band in the wavelength range of 1.57 μm. Figure 10 is a graph showing the analysis results for carbon monoxide. In the graph on the left side of Figure 10, line 141 shows the result of linear fitting based on equation (8) to the absorbance of the R branch, and in the graph on the right side of Figure 10, line 142 shows the result of linear fitting based on equation (8) to the absorbance of the P branch. From Figure 10, it can be understood that the linear fitting based on equation (8) to the absorbance of carbon monoxide (CO) has been performed correctly.

[0060] Based on the analysis using equation (8) above, the estimated temperature T for carbon monoxide (CO) was 294.3K, which is close to the reference temperature of 296K according to the HITRAN database.

[0061] The results of the analysis of carbon dioxide (CO2) based on equation (8) will be explained with reference to Figures 11 and 12. Figure 11 shows the absorbance spectrum of carbon dioxide (indicated by 150). Carbon dioxide (CO2) has an absorption band in the 4.3 μm wavelength range. Figure 12 is a graph showing the analysis results of carbon dioxide (CO2). In the graph on the left side of Figure 12, line 151 shows the result of linear fitting based on equation (8) to the absorbance of the R branch, and in the graph on the right side of Figure 12, line 152 shows the result of linear fitting based on equation (8) to the absorbance of the P branch. From Figure 12, it can be understood that the linear fitting based on equation (8) to the absorbance of carbon dioxide (CO2) has been performed correctly.

[0062] Based on the analysis using equation (8) above, the estimated temperature T for carbon dioxide (CO2) was 292.1K, which is close to the reference temperature of 296K according to the HITRAN database.

[0063] The results of the analysis of hydrogen chloride (HCl) based on equation (8) will be explained with reference to Figures 13 and 14. Figure 13 shows the absorbance spectrum (indicated by 160) of hydrogen chloride (HCl). Hydrogen chloride (HCl) has an absorption band in the 3.5 μm wavelength range. Figure 14 is a graph showing the analysis results of hydrogen chloride (HCl). In the graph on the left of Figure 14, line 161 shows the result of linear fitting based on equation (8) to the absorbance of the R branch, and in the graph on the right of Figure 14, line 162 shows the result of linear fitting based on equation (8) to the absorbance of the P branch. From Figure 14, it can be understood that the linear fitting based on equation (8) to the absorbance of hydrogen chloride (HCl) has been performed correctly.

[0064] Based on the analysis using equation (8) above, the estimated temperature T for hydrogen chloride (HCl) was 294.4 K, which is close to the reference temperature of 296 K according to the HITRAN database.

[0065] From the analysis results shown above, it can be understood that the temperature calculation method (ILRDT method) based on equation (8) according to this embodiment is applicable to multiple types of gases (multi-gas).

[0066] The temperature calculation method (ILRDT method) based on equation (8) shown in the above embodiment is effective not only for dual-comb spectroscopy but also for thermodynamic temperature determination based on the spectral analysis of gas molecules.

[0067] Figure 15 is a flowchart showing the temperature calculation process (temperature calculation processing) using the temperature calculation method (ILRDT method) based on equation (8) described above. This temperature calculation processing is performed under the control of the temperature measurement unit 40a (processor) of the PC40.

[0068] First, in the measurement system 300, the temperature measurement unit 40a (processor) of the PC 40, which constitutes the temperature measurement device 200, performs measurement processing on the gas to be measured using dual-comb spectroscopy and obtains the absorbance spectrum of the gas to be measured (step S1). Then, based on the obtained absorbance spectrum, the temperature measurement unit 40a applies linear fitting with the rotational quantum number J to the integrated absorbance using the ILRDT method and calculates the temperature (step S2).

[0069] Furthermore, the temperature measurement unit 40a of the PC40 can also perform the temperature measurement process according to the above embodiment using the absorption spectrum of gas molecules obtained by an analysis method other than dual-comb spectroscopy, or by acquiring the absorption spectrum of gas molecules obtained by an analysis method other than dual-comb spectroscopy from an external measuring device.

[0070] PC40 has a hardware configuration as a general computer, including a processor, ROM, RAM, memory unit, display unit, operation unit, input / output interface, network interface, etc. The digitizer 30 may have a configuration that includes not only the function of rapidly sampling analog signals (function as an interference wave acquisition unit) but also the function of an oscilloscope. The digitizer 30 may also have a hardware configuration as a general computer, including a processor, ROM, RAM, memory unit, display unit, operation unit, input / output interface, network interface, etc.

[0071] Although the present invention has been described above using typical embodiments, those skilled in the art will understand that modifications to the above embodiments and various other modifications, omissions, and additions can be made without departing from the scope of the present invention.

[0072] In the above-described embodiment, an example configuration was shown in which the function of a temperature measuring device 200 is realized by a digitizer 30 and a PC 40. However, there can be various configurations for the device that realizes the function of a temperature measuring device 200. For example, a temperature measuring device may be realized by a device that integrates the functions of a digitizer 30 and a PC 40.

[0073] The program that performs various processes such as temperature measurement in the above-described embodiment can be recorded on various computer-readable recording media (for example, semiconductor memory such as ROM, EEPROM, and flash memory, magnetic recording media, optical discs such as CD-ROM and DVD-ROM). [Explanation of Symbols]

[0074] 10 Dual-comb generator 11. Tracking optical comb 12 Local Optical Com 21, 22 Erbium-doped fiber amplifier 23, 26 Polarizing Beam Splitter 24 gas cells 25 Bandpass Filter 27 Balanced photodetector 28 Low-noise amplifier 30 digitizers 40 PC 40a Temperature measurement unit 200 Temperature measuring device 300 Measurement Systems

Claims

1. A method for measuring the temperature of gas molecules, The absorbance spectrum of the gas molecules to be measured is obtained, Absorbance A used in temperature estimation of gas molecules by RDT method ｍａｘ The equation: [Math 1] Here, β(NL, T, μ) ν ) is the constant of proportionality, h is Planck's constant c is the speed of light in a vacuum. B tilde is the rotational constant, k Ｂ is the Boltzmann constant, T is thermodynamic temperature. J is the rotational quantum number, m is the energy level number (index number) of the molecule. g Ｉ Spin multiplicity, F(m) is the correction term, Regarding β(NL,T,μ) ν To reduce the contribution of ), both sides of the above equation are integrated with respect to the wavenumber, and the integrated absorbance α of the above equation is obtained. ０ The expression (eq1) represents: [Math 2] Here, A (ν tilde) is the absorbance spectrum of the gas molecule being measured. By transforming the equation and taking the natural logarithm of both sides, we obtain equation (eq2): [Math 3] Based on this, the integrated absorbance α ０ A method for measuring the temperature of a gas molecule, wherein the thermodynamic temperature T of the gas molecule to be measured is estimated by applying a linear fitting using the rotational quantum number J to the gas molecule.

2. Assuming that the contribution of F(m) to temperature estimation is negligible, equation (eq2) is changed to the following equation (eq3): [Math 4] It transforms into this, Based on equation (eq3), the integrated absorbance α ０ A method for measuring the temperature of a gas molecule according to claim 1, wherein a linear fitting using the rotational quantum number J is applied to estimate the thermodynamic temperature T of the gas molecule to be measured.

3. A device for measuring the temperature of gas molecules, The absorbance spectrum of the gas molecules to be measured is obtained, Absorbance A used for estimating the temperature of gas molecules by the RDT method ｍａｘ Equation of: [Math 5] Here, β(NL, T, μ ν ) is the constant of proportionality, h is Planck's constant c is the speed of light in a vacuum. B tilde is the rotational constant, k Ｂ is the Boltzmann constant, T is thermodynamic temperature. J is the rotational quantum number, m is the energy level number (index number) of the molecule. g Ｉ Spin multiplicity, F(m) is the correction term, Regarding β(NL,T,μ) ν To reduce the contribution of ), both sides of the above equation are integrated with respect to the wavenumber, and the integrated absorbance α of the above equation is obtained. ０ The expression (eq1) represents: [Math 6] Here, A (ν tilde) is the absorbance spectrum of the gas molecule being measured. By transforming the equation and taking the natural logarithm of both sides, we obtain equation (eq2): [Number 7] Based on this, the integrated absorbance α ０ The system includes a temperature measurement unit that applies linear fitting using the rotational quantum number J to estimate the thermodynamic temperature T of the gas molecules being measured. Temperature measuring device.

4. The temperature measuring unit is Assuming that the contribution of F(m) to temperature estimation is negligible, equation (eq2) is changed to the following equation (eq3): [Number 8] It transforms into this, Based on equation (eq3), the integrated absorbance α ０ The temperature measuring device according to claim 3, wherein linear fitting by rotational quantum number J is applied to estimate the thermodynamic temperature T of the gas molecules to be measured.

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