Semiempirical Calculations of theHe*(2S3 and 2S1)+ArIonization Total Cross Sections

Abstract

The ionization (associative and Penning) total cross sections for ${\mathrm{He}}^{*}\left(2\mathrm{}{}_{}{}^3{}_{}{}^{}S\right)+\mathrm{Ar}$ and ${\mathrm{He}}^{*}\left(2\mathrm{}{}_{}{}^1{}_{}{}^{}S\right)+\mathrm{Ar}$ have been calculated from ${10}^{-3\mathrm{}}$ to ${10}^4$ eV and compared with experimental data. The classical calculations used interaction potentials that agreed with ab initio theoretical calculations for the repulsive wall, possessed the correct long-range energy dependence, and were in agreement with glory-scattering experiments. The coupling width was an exponential with its free parameter determined by the thermal-energy ionization cross section for each system. The calculations were then extended over a wide range of energies. It was found that as the collision energy increased at the very low energies, the cross sections decreased until about 0.1 eV where they began slowly to rise. As the collision energy is further increased, the cross sections reach a maximum of about 15 ${\mathrm{\AA }}^2$ around 10 eV, and then decrease again at higher energies. The cross sections predicted by the high-energy results, 100-1500 eV, are compared with the data of Moseley, Peterson, Lorents, and Hollstein (preceding paper) and are found to agree within 20% and to have a similar energy dependence.