Collisional electron detachment from NO− by rare gases

Abstract

A model is proposed to explain earlier measurements of electron detachment from NO− by He, Ne, and several diatomic and triatomic molecules. The measurements have been extended to include detachment by Ar with a rate constant of 2×10−14cm3s−1 at 500K. The previously puzzling inefficiencies are satisfactorily explained by a mechanism in which NO− (v=0) is vibrationally excited to NO− (v=1), followed by autodetachment. The data are analyzed with Landau–Teller theory after invoking the principle of detailed balance. Ab initio calculations of the NO− interactions potentials with He, Ne, and Ar have been made. Range parameters derived from Landau–Teller plots and ab initio calculations are in the range expected although not in exact agreement. The ab initio potential attractive wells make clear why the necessary vibrational excitations in He and Ne collisions with NO− (and hence collisional detachment) are far more effective than in the case for Ar. This appears to be the first application of Landau–Teller theory to a negative ion.