Resonance and reversibility of vibrational relaxation of HF in high temperature Ar bath gas

Journal article, 2002

The Boltzmann averaged rate constants for total vibrational relaxation of HF(v = 1) in collisions with Ar are computed in the range of temperatures between 100 and 1500 K. The computed rate constants overestimate the experimental measurements at high temperatures by a large factor. It is concluded that the deviation between theory and experiment cannot be explained by inaccuracy of the PES or dynamical approximations made. It is shown that increasing initial rotational energy enhances a resonant character of the vibrational energy transfer to a great extent. An assumption is made that total vibrational relaxation of HF(v = 1) at high temperatures is determined by competition between vibrational relaxation to a resonant level (v = 0,jres), vibrational excitation from the resonant level, and purely rotational relaxation of HF(v = 0,jres). It is demonstrated that at high temperatures the latter process can be significantly slower than vibrationally inelastic transitions and rotational relaxation of HF(v = 0,jres) may in fact be a rate-limiting stage of vibrational relaxation.