The photoacoustic (PA) method is widely used in studies of the absorption of optical radiation by various media. As a rule, it is assumed that the PA signal is formed due to the relaxation of vibrationally excited molecules with a common characteristic time tVT. The kinetics of heat release in a PA cell at absorption of a laser radiation pulse in a mixture of two molecular gases with two independent channels of vibrational-translational relaxation with very different times is considered. An example of calculations of the kinetics of heat release for a mixture of H2O and CO2 at absorption of a CO2 laser radiation pulse and variations in gas concentrations is presented. It is shown that it is necessary to take into account the relationship between the laser pulse duration and the characteristic times of vibrational-translational relaxation in the gas mixture under study.
gas analysis, laser pulse duration, photoacoustic signal, molecular absorption, VT relaxation, CO2 laser
1. Nemets V.M., Pastor A.A. Lazery v analitike: vozmozhnosti i perspektivy razvitiya impul'snykh lazerov ul'trakorotkogo diapazona // Khimicheskaya fizika. 2017. V. 36, N 2. P. 70–74. DOI: 10.7868/S0207401X17020157.
2. Hongda Li., Konovalov I.N., Panchenko Yu.N., Puchikin A.V., Andreev M.V., Bobrovnikov S.M. Impul'snyi SO2-lazer s nakachkoi prodol'nym razryadom v peremennom magnitnom pole // Optika atmosf. i okeana. 2023. V. 36, N 11. P. 953–957. DOI: 10.15372/AOO20231112; Hongda Li, Konovalov I.N., Panchenko Yu.N., Puchikin A.V., Andreev M.V., Bobrovnikov S.M. Pulsed CO2 laser pumped by a longitudinal discharge in an alternating magnetic field // Atmos. Ocean. Opt. 2024. V. 37, N 1. P. 118–122.
3. Gao R., Liu Ya., Qi S., Song L., Meng J., Liu Ch. Influence mechanism of the temporal duration of laser irradiation on photoacoustic technique: A review // J. Biomed. Opt. 2024. V. 29, N S1. P. S1 1530-1–S1 1530-19. DOI: 10.1117/1.JBO.29.S1.S11530.
4. Kozintsev V.I., Belov M.L., Gorodnichev V.A., Fedotov Yu.V. Lazernyi optiko-akusticheskii gazoanaliz mnogokomponentnykh gazovykh smesei. M.: Izd-vo MGTU im. N.E. Baumana, 2003. 352 p.
5. Ponomarev Yu.N., Ageev B.G., Zigrist M.V., Kapitanov V.A., Kurtua D., Nikiforova O.Yu. Lazernaya optiko-akusticheskaya spektroskopiya mezhmolekulyarnykh vzaimodeistvii v gazakh / pod red. L.N. Sinitsy. Tomsk: RASKO, 2000. 200 p.
6. Mitrayana D., Nikita J.G., Wasono M.A.J., Satriawan M. CO2 laser photoacoustic spectrometer for measuring ethylene, acetone, and ammonia in the breath of patients with renal disease // Sens. Bio-Sens. Res. 2020. V. 30, N 100387. DOI: 10.1010/j.sbsr.2020. 100387.
7. Ageev B.G., Sapozhnikova V.A., Gruzdev A.N., Savchuk D.A. Khronologii gazovykh sostavlyayushchikh v drevesnykh kol'tsakh spilov listvennykh derev'ev // Optika atmosf. i okeana. 2023. V. 36, N 7. P. 602–609. DOI: 10.15372/AOO20230710; Ageev B.G., Sapozhnikova V.A., Gruzdev A.N., Savchuk D.A. Chronologies of gas components in deciduous tree rings // Atmos. Ocean. Opt. 2023. V. 36, N 6. P. 816–823.
8. Burenin A.V. Teoreticheskii analiz gazovoi yacheiki radiospektroskopa s akusticheskim detektorom // Izv. vuzov. Radiofiz. 1974. V. XVII, N 9. P. 1291–1303.
9. Vereshchagina L.N., Zharov V.P., Shipov G.I., Shtepa V.I. Osobennosti impul'snogo optiko-akusticheskogo effekta v gazakh // Zhurn. teor. fiz. 1984. V. 54, N 2. P. 342–347.
10. Cotterell M.I., Ward G.P., Hibbins A.P., Haywood J.M., Wilson A., Langridge J.M. Optimizing the performance of aerosol photoacoustic cells using a finite element model. Part 1: Method validation and application to single-resonator multipass cells // Aerosol Sci. Tech. 2019. V. 53, N 10. Р. 1107–1127. DOI: 10.1080/02786826.2019.1650161.
11. Liu X., Wu H., Dong L. Methodology and applications of acousto-electric analogy in photoacoustic cell design for trace gas analysis // Photoacoustics. 2023. V. 30. P. 100475. DOI: 10.1016/j.pacs.2023.100475.
12. Protasevich A.E. Utochnenie nekotorykh analiticheskikh reshenii dlya optiko-akusticheskogo signala v zhidkostyakh i gazakh // Optika atmosf. i okeana. 2010. V. 23, N 11. P. 1021–1026.
13. Kuryak A.N., Pomazkin D.A., Tikhomirov B.A. Generatsiya signala optiko-akusticheskogo detektora v smesyakh pogloshchayushchego gaza s vodorodom // Optika atmosf. i okeana. 2022. V. 35, N 9. P. 730–734. DOI: 10.15372/AOO20220906.
14. Bauer H.-J. Son et lumiere or the optoacoustic effect in multilevel systems // J. Chem. Phys. 1972. V. 57, N 8. Р. 3130–3145.
15. Rooth R.A., Verhage A.J.L., Wouters L.W. Photoacoustic measurement of ammonia in the atmosphere: Influence of water vapor and carbon dioxide // Appl. Opt. 1990. V. 29, N 25. P. 3643–3653.