H₂-broadening coefficients in the v₃ band of CH₃D at low temperatures

Using a diode-laser spectrometer, we have measured H-broadening coefficients of CHD at low temperatures (153.5, 183.5, and 223.5 K) for four lines in the v band. The collisional widths are obtained by fitting each absorption line with three lineshape models: the Voigt, Rautian, and Galatry profiles. The broadening coefficients are also calculated on the basis of a semiclassical model of interacting linear molecules by considering an atom-atom Lennard-Jones potential in addition to electrostatic contributions. By comparing the broadening coefficients at room and low temperatures the temperature dependence of these broadenings has been determined both experimentally and theoretically.