Diode-laser measurements and calculations of H2-broadening coefficients in the ν3 band of CH3D

Using a tunable diode-laser spectrometer, we have measured at room temperature the H-2-broadening coefficients of (CH3D)-C-12 for 36 lines belonging to P-Q and R-Q branches in the v(3) parallel band. The recorded lines with J values ranging from I to 15 and K from 0 to 9 (K less than or equal to J) are located between 1196 and 1412 cm(-1). The H-2-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 greater than or equal to 3 where they are underestimated. The latter discrepancy may be caused by the assumption to consider only DeltaK = 0 collision-induced transitions, associated with \DeltaJ\ transitions up to 4. (C) 2002 Elsevier Science (USA). All rights reserved.