Excitation of helium by 20-100 keV hydrogen atoms

Abstract
The excitation of helium by 20-100 keV hydrogen atoms has been investigated by the spectroscopic analysis of radiation emitted in the spectral range 3900-6000 AA during the spontaneous decay of the excited products of single collisions. Absolute cross sections for the excitation of the 41S, 41D, 43S and 43D levels have been determined. In the case of the 41S and 41D levels, cross sections for excitation by protons and hydrogen atoms have been compared with a relative accuracy of +or-12%. The measured cross sections are in generally poor accord with recent theoretical estimates.