The paper considers the possible structure of the water vapor continuum absorption. The continuum absorption within the v2 H2O band and in its high-frequency wing was calculated based on the asymptotic line wing theory (ALWT) taking into account the violation of the long-wave approximation for the centers of mass of molecules. To explain the spectral and temperature behavior of the continuum absorption coefficient, the same line profile was used throughout the entire frequency range under study. The results are important for problems of spectroscopy and radiation propagation in different media.
continuum absorption, v2 H2O band, temperature behavior, line wing, dimer absorption
1. Burch D.E. Continuum absorption by atmospheric H2O // Proc. SPIE. 1981. V. 277. P. 28–39.
2. Tobin D.C., Strow L.L., Lafferty W.J., Olson W.B. Experimental investigation of the self- and N2-broadened continuum within the v2 band of water vapor // Appl. Opt. 1996. V. 35, N 24. P. 4724–4734. DOI: 10.1364/AO.35.004724.
3. Paynter D.J., Ptashnik I.V., Shine K.P., Smith K.M., McPheat R.M., Williams R.G. Laboratory measurements of the water vapor continuum in the 1200–8000 cm-1 region between 293 K and 351 K // J. Geophys. Res. 2009. V. 114. P. D21301. DOI: 10.1029/2008JD011355.
4. Ptashnik I.V., Petrova T.M., Ponomarev Yu.N., Shine K.P., Solodov A.A., Solodov A.M. Near-infrared water vapour self-continuum at close to room temperature // J. Quant. Spectrosc. Radiat. Transfer. 2013. V. 120. P. 23–35. DOI: 10.1016/j.jqsrt.2013.02.016.
5. Ptashnik I.V., Klimeshina T.E., Petrova T.M., Solodov A.A., Solodov A.M. Kontinual'noe pogloshchenie vodyanogo para v polosah 2.7 i 6.25 mm pri ponizhennyh temperaturah // Optika atmosf. i okeana. 2015. V. 28, N 9. P. 772–776. DOI: 10.15372/AOO20150902; Ptashnik I.V., Klimeshina T.E., Petrova T.M., Solodov A.A., Solodov A.M. Water vapor continuum absorption in the 2.7 and 6.25 mm bands at decreased temperatures // Atmos. Ocean. Opt. 2016. V. 29, N 3. P. 211–215.
6. Ptashnik I.V., Klimeshina T.E., Solodov A.A., Vigasin A.A. Spectral composition of the water vapour self-continuum absorption within 2.7 and 6.25 mm bands // J. Quant. Spectrosc. Radiat. Transfer. 2019. V. 228. P. 97–105. DOI: 10.1016/j.jqsrt.2019.02.024.
7. Simonova A.A., Ptashnik I.V., Shine K.P. Semi-empirical water dimer model of the water vapour self-continuum within the IR absorption bands // J. Quant. Spectrosc. Radiat. Transfer. 2024. V. 329. P. 109198. DOI: 10.2139/ssrn.4826877.
8. Bignell K.J. The water-vapor infrared continuum // Q. J. Roy. Meteor. Soc. 1970. V. 96, N 409. P. 390–403.
9. Burch D.E., Gryvnak D.A., Pembrock J.D. Investigation of the absorption of infrared radiation by atmospheric gases: Water, nitrogen, nitrous oxide. AFCRL-71-0124 Semi-Annual Technical Report N 2. 1971.
10. Watkins W.R., White K.O., Bower L.R., Sojka B.Z. Pressure dependence of the water vapor continuum absorption in the 3.5–4.0 mm region // Appl. Opt. 1979. V. 18, N 8. P. 1149–1160.
11. Burch D.E., Alt R.L. Continuum absorption by H2O in the 700–1200 and 2400–2800 cm-1 windows. Report N AFGL-TR-84-0128. 1984. 31 p.
12. Baranov Yu.I., Lafferty W.J. The water-vapor continuum and selective absorption in the 3–5 mm spectral region at temperatures from 311 to 363 K // J. Quant. Spectrosc. Radiat. Transfer. 2011. V. 112, N 8. P. 1304–1313.
13. Ptashnik I.V., McPheat R.A., Shine K.P., Smith K.M., Williams R.G. Water vapor self-continuum absorption in near-infrared windows derived from laboratory measurements // J. Geophys. Res.: Atmos. 2011. V. 116. P. D16305. DOI: 10.1098/rsta.2011.0218
14. Campargue A., Kassi S., Mondelain D., Vasilchenko S., Romanini D. Accurate laboratory determination of the near infrared water vapor self-continuum: A test of the MT_CKD model // J. Geophys. Res.: Atmos. 2016. V. 121. P. 13180–13203. DOI: 10.1002/2016JD025531.
15. Richard L., Vasilchenko S., Mondelain D., Ventrillard I., Romanini D., Campargue A. Water vapor self-continuum absorption measurements in the 4.0 and 2.1 mm transparency windows // J. Quant. Spectrosc. Radiat. Transfer. 2017. V. 201. P. 171–179. DOI: 10.1016/j.jqsrt.2017.06.037.
16. Lechevallier L., Vasilchenko S., Grilli R., Mondelain D., Romanini D., Campargue A. The water vapour self-continuum absorption in the infrared atmospheric windows: New laser measurements near 3.3 and 2.0 mm // Atmos. Meas. Tech. 2018. V. 11. P. 2159–2171. DOI: 10.5194/amt-11-2159-2018.
17. Bogdanova Yu.V., Klimeshina T.E., Rodimova O.B. Dimernoe pogloshchenie v IK-polosah vodyanogo para // Optika atmosf. i okeana. 2019. V. 32, N 10. P. 801–807. DOI: 10.15372/AOO20191001; Bogdanova Yu.V., Klimeshina T.E., Rodimova O.B. Dimer absorption within water vapor bands in the IR region // Atmos. Ocean. Opt. 2020. V. 33, N 2. P. 134–140.
18. Rodimova O.B. Pogloshchenie dimerami vody v IK-polosah vodyanogo para pri razlichnyh temperaturah // Optika atmosf. i okeana. 2023. V. 36, N 2. P. 86–92. DOI: 10.15372/AOO20230202; Rodimova O.B. Absorption by water dimers in water vapor IR spectra at different temperatures // Atmos. Ocean. Opt. 2023. V. 36, N 4. P. 293–299.
19. Tretyakov M.Yu., Serov E.A., Odintsova T.A. Equilibrium thermodynamic state of water vapor and the collisional interaction of molecules // Radiophys. Quant. Electron. 2012. V. 54, N 10. P. 700–716. DOI: 10.1007/s11141-012-9332-x.
20. Ruscic B. Active thermochemical tables: Water and water dimer // J. Phys. Chem. A. 2013. V. 117. P. 11940–11953. DOI: 10.1021/jp403197t.
21. Leforestier C. Water dimer equilibrium constant calculation: A quantum formulation including metastable states // J. Chem. Phys. 2014. V. 140, N 7. P. 074106-1–074106-9. DOI: 10.1063/1.4865339.
22. Simonova A.A., Ptashnik I.V., Elsey J., McPheat R.A., Shine K.P., Smith K.M. Water vapour self-continuum in near-visible IR absorption bands: Measurements and semiempirical model of water dimer absorption // J. Quant. Spectrosc. Radiat. Transfer. 2022. V. 277. P. 107957. DOI: 10.1016/j.jqsrt.2021.107957.
23. Nesmelova L.I., Rodimova O.B., Tvorogov S.D. Kontur spektral'noi linii i mezhmolekulyarnoe vzaimodeistvie. Novosibirsk: Nauka, 1986. 216 p.
24. Gordov E.P., Tvorogov S.D. Metod poluklassicheskogo predstavleniya kvantovoi teorii. Novosibirsk: Nauka, 1984. 167 p.
25. Bogdanova Yu.V., Rodimova O.B. Line shape in far wings and water vapor absorption in a broad temperature interval // J. Quant. Spectrosc. Radiat. Transfer. 2010. V. 111. P. 2298–2307. DOI: 10.1016/j.jqsrt.2010.05.005.
26. Klimeshina T.E., Rodimova O.B. Raschet kontinual'nogo pogloshcheniya Н2О v IK-diapazone na osnove izmerenii Bercha // Optika atmosf. i okeana. 2019. V. 32, N 8. P. 628–632. DOI: 10.15372/AOO20190804.
27. Tvorogov S.D. Problema tsentrov mass v zadache o konture spektral'nyh linii. I. Sushchestvovanie dlinnyh traektorii // Optika atmosf. i okeana. 2009. V. 22, N 5. P. 413–419.
28. Bogdanova Yu.V., Klimeshina T.E., Rodimova O.B. Pogloshchenie v kryl'yah polos vodyanogo para i narushenie dlinnovolnovogo priblizheniya dlya tsentrov mass molekul // Optika atmosf. i okeana. 2016. V. 29, N 10. P. 805–815. DOI: 10.15372/AOO20161001; Bogdanova Yu.V., Klimeshina T.E., Rodimova O.B. Water vapor line wing absorption and violation of the long-wave approximation for molecular centers of mass // Atmos. Ocean. Opt. 2017. V. 30, N 2. P. 111–122.