This paper describes the results of two closely related trajectory studies of the ArOCS system simulating (a) deactivation of OCS(0110) in thermal collisions with Ar, and (b) dissociation and energy transfer in the ArOCS van der Waals complex. Both studies used a potential surface which sums together an accurate OCS potential with an empirically determined Ar + OCS interaction potential. Two parametrizations of the surface are studied, and one of them (surface II) is found to match all the known properties of ArOCS complex as well as the results of ab initio calculations quite well. Collisional deactivation of OCS(0110) by Ar is studied using the quasiclassical trajectory method. A recently developed fast Fourier transform (FFT) method for determining the vibration/rotation good action variables in OCS is used to determine the deactivation transition probability in these collisions, and the resulting value on our better surface (0.5 × 10-4) is quite close to the measured value (0.96 × 0.3) × 10-4. Semiclassical eigenvalues for OCS are also calculated using the FFT method, and the results are within 0-8 cm-1 of accurate quantal values for states within 2500 cm-1 of the ground state. The ArOCS van der Waals cluster simulation is also done using quasiclassical trajectories, with OCS excited to either the 0200 or 0220 state and the Ar-OCS stretch and bend states varied over a wide range of energies from zero point to 90% of dissociation. In none of these simulations was either dissociation or intramolecular energy transfer important on a time scale of at least 15 ps and very likely 100 ps. This indicates that the 5.4 ps lifetime which appears to govern the absorption linewidth of ArOCS does not arise from either vibrational predissociation or intramolecular energy transfer.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry