Influence of adiabatic interactions on the energy transfer in molecular collisions

Abstract

Synopsis A description of slow molecular collisions is given, based on the assumption that the molecular interaction can be divided into an “adiabatic” and a “non-adiabatic” part. The adiabatic interaction has in general the twofold effect of changing the relative motion of the collision partners and of perturbing their internal states. The non-adiabatic interaction gives rise to transitions between the perturbed internal states. Each of the effects due to the adiabatic interaction can contribute to an increased probability of energy transfer between the translation and the internal states. The method is applied to head-on collisions of HCl molecules with dipole-dipole interaction and of CO molecules with quadrupole-quadrupole interaction as adiabatic forces. Increases in the vibrational deactivation probabilities by factors of 4 and 2, respectively, are found as a result of these interactions. The interactions give rise only to the “acceleration” effect; they are not strong enough to induce internal perturbations.