Electron-transfer cross sections to low-lying excited states of hydrogen in collisions of protons with helium and argon

Abstract
The emission intensities of the four lowest Lyman lines (Ly- alpha , Ly- beta , Ly- gamma and Ly- sigma ) of atomic hydrogen produced in electron-transfer collisions of 2-15 keV protons on helium and argon were measured. By applying an electric field in the direction of the ion beam, excited states of hydrogen for a particular level n were Stark-mixed and the effects on the emission intensities were studied. Electron-transfer cross sections were evaluated from the intensity measurements for hydrogen states with principal quantum numbers 2 to 5. Additional information about the angular momenta of these excited states could be derived from the intensity measurements carried out with the electric field. No polarisation measurements were made. The behaviour of the cross sections as a function of principal quantum number was studied.