Electron-detachment cross sections to low-lying excited states of hydrogen in collisions of negative hydrogen ions with helium and argon

Abstract

The intensities of the four lowest Lyman lines (Ly- alpha , Ly- beta , Ly- gamma and Ly- delta ) of atomic hydrogen produced in electron-detachment collisions of 1-6 keV negative hydrogen ions on helium and argon were measured. By applying an electric field in the direction of the ion beam, excited states of hydrogen were Stark-mixed and the effects on the emission intensities were studied. Electron-detachment cross sections were evaluated from the intensity measurements for states of principal quantum numbers 2 to 5. For both gases, electron detachment to the 2p1/2,3/2 state is much larger than detachment to the 2s1/2 state. The preference for 2p1/2,3/2 excitation also occurs with respect to detachment to the higher np1/2, 3/2 (n=3-5) states of the hydrogen atom.