Calculated line broadening parameters for methane perturbed by diatomic molecules

Abstract

We report semiclassical line broadening calculations for methane perturbed by diatomic molecules: nitrogen, N2, oxygen, O2 and hydrogen, H2, at room temperature. For this, we have developed a symmetrized version of the Robert and Bonamy theory. The interaction potential was built from electrostatic (octopole and hexadecapole for methane, quadrupole for the diatomic molecules) and atom–atom contributions. The relative (classical) trajectories of the molecules were computed in the frame of the usual parabolic model, through analytical formula. High orders of developments had to be used for the short range molecular interactions in the case of N2 and O2. For H2, a lower order of development was found to be convenient. We have compared our calculations to some of the available experimental data for hydrogen and oxygen. For nitrogen, we have already reported some comparisons to measurements [T. Gabard, V. Boudon, J. Quant. Spectrosc. Radiat. Transfer 111 (2010) 1328–1343]. Thus, we report here new extensive calculations for the dyad (near 1300cm−1) and the pentad (near 3000cm−1) spectral regions.