Pressure Lineshift and Broadening Coefficients in the 2nu(3) Band of (16)O(12)C(32)S

In this study we report the first measurements of the pressure-induced lineshift coefficients due to Ar, He, O(2), and N(2) for 22 rovibrational lines from P(53) to R(53), belonging to the 2nu(3) band of (16)O(12)C(32)S at 4100 cm(-1). The lineshift results were obtained from the simultaneous record of the pressure-broadened and pure low-pressure OCS lines, using a tunable difference-frequency laser spectrometer. For four lines of the 2nu(3) band we also report Ar-, He-, O(2)-, and N(2)-broadening coefficients by fitting Voigt and Rautian profiles to the measured shapes of these lines. The broadening and shift coefficients are compared to the results of theoretical calculations based on the semiclassical Robert-Bonamy formalism and two different isotropic and anisotropic intermolecular potentials. For OCS-Ar we also consider the Smith-Giraud-Cooper model including all orders of the interaction within the peaking approximation. In all cases, the calculated broadening coefficients are in reasonable agreement with the experimental data. By considering adjustable parameters for the vibrational dependence of the isotropic potential, the general trends of the lineshifts with J can be roughly predicted, except at low J values where an asymmetry behavior for P and R branches is generally observed. Copyright 2000 Academic Press.