Semiempirical model for angular distribution of electrons emitted in metastable atom-atom collisions

Electron angular distributions from ionization in collisions of He(21,3S) and Ar(¹S) have been studied in terms of molecular-orbital correlation diagrams and a semiclassical and probabilistic model for the collision process. Consideration of the united-atom limit for this system indicates that the electronic angular momenta λ=0, 1, and 2 play an important role. The interaction potential responsible for electron emission was assumed to decrease exponentially with increasing distance, and was parametrized by fitting experimental results at a fixed collision energy. The values of the parameters show that λ=0 is the dominant partial wave and lead to backward-peaked distributions. Calculations performed at other energies show an increasing anisotropy with increasing collision energies.