Electron-energy spectra of H- doubly excited states resulting from collisions of H- with He

Electron-energy spectra for H- doubly excited states resulting from collisions of H- with He are rigorously calculated within a semiclassical molecular representation by including couplings between doubly excited states and continuum states and their interference with direct-detachment processes. An energy sampling procedure, based on the Gauss quadratures, is used to discretize continuum states. The present theoretical result clarifies mechanisms of excitation to doubly excited states, quantitatively reproduces the experimental spectra first observed by Risley and Geballe in 1974, separates the contributions from each of three doubly excited states, and identifies the cause of the interference between channels arising from double-electron excitation and direct detachment with simultaneous excitation