Energy dependence of the spin asymmetry for electron impact ionization of atomic hydrogen and its implications for the Wannier theory of double escape

The authors extend the formalism introduced by Klar and Schlecht (1976) and more completely developed by Rau and Greene (1982, 1983) to explore the implications of the Wannier threshold theory for the spin dependence of electron impact ionization of atomic hydrogen. By analysing the properties of the contributions to the singlet and triplet cross sections from the multiplicity of (L, S pi ) final states and by combining the results of the investigations of spin-asymmetry measurements of Guo et al. (1990, 1993) and the earlier investigations of spin-averaged cross section measurements of McGowan and Clarke (1968), the authors are able to provide insight into the role played by higher order terms and the possible influence of collisional dynamics. The authors further show that the critical energy above threshold at which the contributions from higher order terms become visible is substantially lower for the singlet and triplet partial cross sections than it is for the spin-averaged cross section.