LAUSR

Abstract Theoretical hydrogen-broadening coefficients and associated temperature exponents for 12 CH 3 D ( J, K ) lines in parallel (Δ K = 0) bands are calculated by a semi-classical approach based on a rigorous consideration of the active molecule as a symmetric top, a model intermolecular potential comprising both short- and long-range interactions, and exact classical trajectories. The leading potential terms are shown to provide a realistic description of line broadening in comparison with scarce measurements available in the literature. The calculations performed for 296, 240 and 190 K are used to extract the line-width temperature-dependence exponents for the typical temperature range of atmospheric interest ∼200–300 K. Detailed P - Q - R -line lists are provided for large intervals of quantum numbers (0 ≤ J ≤ 20, 0 ≤ K ≤ J ) requested for remote sensing of planetary atmospheres, in particular those of outer planets and their moons. With negligible vibrational dependence of CH 3 D line-widths and estimated as negligible their sub-branch dependence, these data can be also employed for perpendicular bands.