Empirical potentials for rovibrational energy transfer of hydrogen fluoride in collisions with argon

Abstract

Rovibrational energy transfer of hydrogen fluoride in collisions with argon was investigated by using the coupled-states approximation to the quantum scattering problem. Empirically determined 3-D ab initio potential energy surfaces (PES) for the interaction between hydrogen fluoride and argon are presented. Second-order Møller-Plesset perturbation theory (MP2) was used to provide an initial approximate PES for the complex. The MP2 PES was subsequently modified to compensate for the underestimated dispersion interaction and adjusted until the desired agreement between calculated and observed spectroscopic quantities was achieved. Calculated rotational cross sections are in good agreement with experimental results as well as those obtained with a highly accurate vibrationally averaged empirical PES [J. M. Hutson, J. Chem. Phys. 96, 6752 (1992)]. The rate constants for the collision induced relaxation of the first vibrational state of hydrogen fluoride are presented as functions of temperature. The rate constants show structure at low temperature corresponding to cross-section resonances. The calculated rate constants are in good agreement with available high temperature experimental results. The calculations provide lower temperature rate constants and a wealth of detailed state-to-state information that are not available from experiment. © 2001 American Institute of Physics.