Theoretical calculation of CH3Br/N2-broadening coefficients at various temperatures

摘要

The N2-broadening coefficients of CH_3~(79)Br and CH_3~(81)Br have been calculated for transitions belonging to the ~PP-, ~PQ-, ~PR-, ~RP-, ~RQ- and ~RR-branches of the v_6 band near 10γm, using a semiclassical impact theory. The intermolecular potential used, includes in addition to the overwhelming electrostatic interactions, induction and dispersion energy contributions, which are significant only for low J transitions with K approaching or equal to J. Comparisons have been performed with the extensive set of previous measurements at room temperature 4. The theoretical results are in satisfactory agreement with the experimental data, and the J and K dependences are reasonably well reproduced. From calculations at 200, 230, 260 and 296K, the temperature exponent of the collisional broadenings derived from a simple power law has been determined for each transition of each sub-branch and compared with a recent experimental evaluation 5. Finally the N_2-broadening coefficients calculated at 296K and their temperature exponents are given as supplementary materials of this paper for atmospheric applications and databases.