Absolute cross sections for the excitation of n¹P-levels of helium by proton impact (150-1000 keV)

Abstract

Excitation of helium ground state atoms to the 21P-, 31P-, and 41P-levels by proton impact has been studied in the energy range of 150 keV to 1000 keV. Total cross sections have been obtained by measuring light intensities resulting from the decay of the excited atoms; the corresponding wavelengths lie in the vacuum ultraviolet region. The apparent excitation functions have been cascade corrected; polarization corrections have not to be considered due to the special mounting of the monochromator. The cross sections have been made absolute by comparing the signal rates resulting from 400 keV proton impact and 1 keV electron impact and using theoretical values for the electron impact cross sections. The results are compared with other experimental and theoretical data.