M. V. Tonkov

Intra- and intermolecular components of the ν2 forbidden band of CF4 in pure gas and in He, Ar, Xe and N2 mixtures

Spectra of CF4 as pure gas and in mixtures with gaseous He, Ar, Xe and N2 were obtained in the region of the forbidden ν2 band at pressures from about 1 atm up to 100 atm at ambient temperature. The absorption consists of two components depending on the gas pressure. The first, with an integrated intensity (cm−2 Amagat−1) that is independent of pressure, arises through the Coriolis or intramolecular interactions. The second, varying linearly with the partial pressure, is attributable to additional absorption arising during intermolecular binary collisions. The intensity of each of these components was measured and analysed, and from the results we are able to draw some conclusions concerning the collision-induced mechanisms responsible for the absorption.

Line mixing in the ν 3 and forbidden ν 2 bands of CH4 in gaseous helium

The paper reports on studies of the possibility of the transfer of the adjustable parameters of the line mixing model describing the ν3 absorption band shape of CH4 in helium to the case of the forbidden ν2 band shape. This transfer provides a reasonable overall agreement with the measured spectra, with deviations greater than the experimental uncertainties remaining in some J-manifolds. The model has been improved by taking into account the mixing of spectral lines with the same initial level. It was found that the description of the shapes of certain manifolds can be improved by fitting corresponding matrix elements of the optical rotational relaxation matrix, providing, in some particular cases, more detailed information on the matrix structure.