Diode-laser measurements and calculations of H₂-broadening coefficients in the v₃ band of CH₃D

Using a tunable diode-laser spectrometer, we have measured at room temperature the H-broadening coefficients of CHD for 36 lines belonging to P and R branches in the v parallel band. The recorded lines with J values ranging from 1 to 15 and K from 0 to 9 (K ≤ J) are located between 1196 and 1412 cm. The H-broadening coefficients were determined by fitting each spectral line with Voigt, Rautian, and Galatry profiles. They were also calculated on the basis of a semiclassical model of interacting linear molecules performed by considering in addition to the weak electrostatic contributions the atom-atom Lennard-Jones potential. The theoretical results are in reasonable agreement with the experimental data, except for high J transitions where they are overestimated and for K approaching or equal to J with J ≥ 3 where they are underestimated. The latter discrepancy may be caused by the assumption to consider only ΔK = 0 collision-induced transitions, associated with |ΔJ| transitions up to 4.