One-electron detachment from H-in collisions with atomic hydrogen and helium

The first Born approximation is used to calculate the cross sections for one-electron detachment from H- in collisions with hydrogen and helium atoms. For H- the Born matrix elements were obtained using polarised-orbital free-state functions with both a 20- and 33-parameter correlated bound-state function. The calculated cross sections differ significantly from previous Born-approximation results. For collisions with helium the present values agree with the measured cross section to better than 30% for energies above about 100 keV. The difference-between theory and experiment is attributed to electron-detachment collisions which leave the residual hydrogen atoms in excited states. A similar effect is also noted for collisions with atomic hydrogen but its magnitude is uncertain since the experimental data are mainly for collisions with molecular hydrogen.