Doubly differential cross section for electron detachment from 0.5-MeV H- in collision with He

We calculate the energy spectrum of electrons detached from 0.5-MeV negative hydrogen ions in collision with helium targets using the plane-wave Born approximation. Three different models for continuum states of H- are used to calculate electron-detachment doubly differential cross sections. The first model uses a single exponential function for the loosely bound electron of H- and a plane wave for the detached electron. The second model is similar to the first one, but the final state is Schmidt orthogonalized. The third model includes the s-wave phase shifts obtained from Schwinger's variational principle. These phase shifts incorporate the radial correlations which are essential for the study of such low-energy continuum electrons. The doubly differential cross section obtained by the second and third models have a double-peak structure. These peaks are at energies different from the ones measured by Menendez and Duncan. Based on this calculation we observe that the ejected electrons are sensitive to the s-wave phase shifts and electron-electron correlations. This observation rejects the use of plane-wave models for the detached electrons and indicates the need for more accurate wave functions which incorporate radial and angular correlations