Theoretical calculations of self-broadening coefficients in the ν6 band of CH3Br

A semiclassical impact theory based upon the Anderson-Tsao-Curnutte formalism has been used to calculate the self-broadening coefficients in the PP-, PQ-, PR-, RP-, RQ- and RR-branches of the ν6 band of 12CH379Br and 12CH381Br near 10 μm. Comparisons have then been performed with the extensive set of previous measurements [3] (Jacquemart et al., 2007). The intermolecular potential used, involving the overwhelming electrostatic contributions, leads to larger results than the experimental data for middle J values. By arbitrarily limiting the integration of the differential cross-section to an impact parameter equal to 29 Å, quite satisfactory results have been obtained, and the J and K dependences are in reasonable agreement with those observed experimentally. The theoretical results are, on the whole, slightly larger for CH379Br than for CH381Br and for same J and K initial states of the transitions they depend on the sub-branch considered. These differences and dependencies were not observed in the previous measurements due to scatter in the experimental data. Finally, the theoretical results obtained for all sub-branches of 12CH379Br and 12CH381Br are given as supplementary materials of this paper.