Collisional Excitation ofAr*+O2Mediated by Ion-Pair Formation

Abstract

For ${\mathrm{Ar}}^{*}$ + ${\mathrm{O}}_{2}$ collisions at \ensuremath{\approx} 100 eV energies an intense rainbow peak has been observed in the neutral-product angular distribution. The surprisingly large inelasticities (1-2 eV) and the absence of elastic scattering in this small-angle feature are explained by a charge-transfer model involving transient formation of an ${\mathrm{Ar}}^{+}$ + ${\mathrm{O}}_{2}^{\ensuremath{-}}$ intermediate. Large product inelasticities are understood by examing the relative timing of the projectile motion and the ${\mathrm{O}}_{2}^{\ensuremath{-}}$ vibration on the intermediate surface.