Equation of Transport for Infrared Radiation in Dense Molecular Gas

Equation of transfer of infrared radiation propagating over a flat surface in a dense molecular gas with small temperature gradients is constructed. Interaction of the radiation field with a gas is manifested in radiative transitions between vibrational, rotational, or vibrational-rotational states of molecules. Therefore, the absorption spectrum of a molecular gas includes hundreds of transitions, and the absorption coefficient as a function of the photon frequency has an oscillatory structure with maxima in the centers of corresponding spectral lines and minima between the centers of neighboring lines. Analysis of the radiative transfer equation for specific problems requires knowledge a large number of parameters for the corresponding radiative transitions in molecules that are contained in the HITRAN data bank. Therefore this equation can be considered as addition to data of the HITRAN bank. The peculiarities of application of the infrared radiation transfer equation to certain cases are analyzed.