Potential energy surface and infrared spectra of OCS–hydrogen complexes

Abstract

We present a full-dimensional potential energy surface for the OCS–H₂ system that includes explicit dependence on the Q ₃ normal vibration of the OCS molecule. From the integration of this potential over the Q ₃ coordinate two vibrationally adiabatic surfaces are generated. These are then used to compute the rovibrational energies for the OCS–H₂ complexes with the OCS molecule in both its ground and first excited vibrational states and for all H₂ isotopomers. Comparison with the available experimental data shows an overall good agreement for all spectroscopic parameters. The full potential energy surface is also integrated over the H₂ angular variables to obtain a reduced dimensionality effective potential that describes the interaction between an OCS molecule and a spherical H₂ molecule. The accuracy of this approximation, widely employed in Monte Carlo simulations of H₂ clusters, is then analysed here in the case of the OCS–H₂ complexes by comparing the rovibrational energies computed with the present potential interaction in both full and reduced dimensionality.

Acknowledgements

This work has been supported by the Chemistry Division of the National Science Foundation (Grant No. CHE-0107541). FP would like to thank Professor Szalewicz and Dr Jankowski for their help at the early stages of the bound state calculations. FORTRAN programs computing the OCS–H₂ potential energy surface in both full and reduced dimensionality are available from the authors upon request.