Kinematic studies of electron transfer processes between alkali atoms and molecules. K+O2

Abstract

Measurements of angle and energy differential cross sections for the reaction K+O2→K++O−2 are reported for collision energies between 0.75 and 30 eV above threshold. The ionization cross section in the forward direction shows two peaks at energy losses of 4.6 and 5.1 eV. While the first peak indicates a maximum transition probability into the 4th to 6th vibrational levels of the ground state O−2[2Πg], the second peak is an indication of an excited O−2 state [4Σu or 2Πu]. With increasing deflection angle the energy loss spectrum shifts toward smaller values. At a collision energy of 14 eV, the angular differential cross section for a fixed energy loss of 5.1 eV has a maximum at a deflection angle of 7.5°; at a 4 eV energy loss, however, the peak is at 22° in the center-of-mass system, dropping off steeply at 25°, which is the rainbow angle. The deflection angle mainly depends on the Coulomb force the particles experience during the collision. For encounters leading to electronically excited O−2 the influence of this force is smaller, leading to smaller rainbow angles than for products formed in the ground state.