Temperature dependence of the probability of vibrational energy exchange between the stretching modes in H 2O/D 2O + Ar collisions

Abstract

The vibrational energy exchange between the stretching modes of H 2O in the H 2O + Ar collision has been studied in a semiclassical method in the temperature range of 200–3000 K. The energy exchange probability increases slowly, but nearly linearly, with temperature over the entire range, reflecting a near-resonant case. The intermolecular removal of the energy mismatch (Δ E = + 105 cm −1) by translation is found to be nearly as efficient as the intermolecular transfer to the rotational motion. The energy exchange probability for D 2O + Ar is less efficiency by a factor of about two over the temperature range in both the intramolecular VR and intermolecular VT processes. The lower efficiency found in the VR step is due to a slower rotational motion of D 2O, while that in the VT process is due to a larger energy mismatch for the D 2O + Ar collision (Δ E = + 122 cm −1). The effect of molecular attraction is found to be important in the energy exchange process especially near room temperature, and the use of empirically determined attractive energies for the H 2O—Ar complex is found to be valuable at such temperatures.