Energy and charge transfer in O+2 on O2 collisions: Effects of a ‘‘vibrational rainbow’’

Abstract

The efficient conversion of up to eight vibrational quanta into translational energy is found to occur during O+2 –O2 collisions. The high efficiency and low deflection angle which are observed in the experiment reported are explained by the occurrence of multiple crossings of the O+2 –O2 system interaction potentials, specifically the attractive and repulsive symmetry potentials. The energy and charge transfer model evolved from the experimental data proposes that energy transfer in symmetric molecule–ion collisions takes place at very large intermolecular separations. It differs in an important way from previous concepts which suggest that impulsive momentum transfer at relatively short distances is necessary to the exchange of vibrational energy. To explain the data, a distortion of the electron cloud surrounding the colliding systems is conceived to produce charge-transfer oscillations whose frequencies at the crossing points are multiples of molecular vibration frequencies. Such resonances are similar to the more familiar rainbows often observed in molecular collisions. The ease with which energy has been found to be transferred between modes of motion in charged systems affects the thermal, optical, and other properties of plasmas.