Vibrational and rotational energy transfer in collisions of vibrationally excited HF molecules with Ar atoms

This work presents converged vibrational close coupling-rotational coupled states calculations of cross sections and rate constants for rotational and vibrational transitions in collisions of vibrationally excited HF molecule s with Ar atoms. Reduced channel basis sets assuming both a lower and an up per cutoff in vibrational quantum number are used for calculations at high internal energies of the diatomic molecule. The most recent potential energ y surface is employed for the calculations and the correspondence of the re sults to the previous investigation of rovibrational dynamics in collisions of HF(v=1) with Ar is examined. It is shown that initial vibrational excit ation stimulates vibrationally inelastic transitions to a great extent whil e the rotational energy transfer is essentially unaffected by initial v-num ber. The cross sections for vibrational relaxation of different vibrational levels of HF are shown to exhibit a strong dependence on initial rotationa l energy which is, however, of different magnitude for different vibrationa l states. The dependence of the vibrational relaxation of HF(v=1,3,6) on th e translational energy of the atomic collision partner is different by an e nergy independent factor for different vibrational levels in the high energ y limit and shows minima at low collision energies. (C) 2001 American Insti tute of Physics.