Velocity dependence of the cross sections for Penning and associative ionization of H atoms byHe(2S1)) metastable atoms

Abstract

The velocity dependence of the Penning and associative ionization cross sections for the $\mathrm{He}\left(2\mathrm{}{}_{}{}^1{}_{}{}^{}S\right)+\mathrm{H}$ interacting system is measured for the relative velocity range 1900-5300 m/sec in a crossed-beam experiment by a time-of-flight technique. We observe that the total ionization cross section decreases monotonically with increasing kinetic energy, and that associative ionization is a minor process, contrary to some theoretical predictions made for the $\mathrm{He}\left(2\mathrm{}{}_{}{}^1{}_{}{}^{}S\right)+\mathrm{H}$ system.