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Atmospheric and Oceanic Optics

2016 year, number 10

Water vapor line wing absorption and violation of the long-wave approximation for molecular centers of mass

Yu.V. Bogdanova, T.E. Klimeshina, O.B. Rodimova
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, 1, Academician Zuev square, Tomsk, 634021, Russia
Keywords: теория крыльев линий, потенциал межмолекулярного взаимодействия, отказ от длинноволнового приближения, НО, СО, континуальное поглощение, line wing theory, intermolecular interaction potential, violation of the long-wave approximation, continuum absorption

Abstract

Further development of the asymptotic line wing theory is presented where the long-wave approximation for the molecular centers of mass is violated. This provides long molecular trajectories going far beyond an elementary volume in the case of the nonresonance light absorption. The occurrence of long trajectories is evidence of a certain degree of ordering of molecular chaos. The latter can be described by means of a modified semiclassical representation method to establish correlation between displacement and velocity operators. An expression for the absorption coefficient is derived that allows an ambiguity concerning the estimation of the parameters of the potentials to be avoided and the temperature dependence of the absorption coefficient in line wings to be described. The calculations under consideration employ a diffusion model for H2O absorption in the 3-5 mm window region and for CO2 absorption in the 4.3 mm band wing to describe the temperature dependence of the absorption coefficient. It is shown that long molecular trajectories significant for the 8-12 and 3-5 mm H2O window regions can hardly play a role in the 4.3 mm CO2 band wing.