Energy per ion pair for electron and proton beams in atomic hydrogen

Abstract

The angular distribution of electrons of given energy ejected by ionization of atomic hydrogen is calculated according to the Born approximation and used in conjunction with similar calculations by Bates, Dalgamo and Griffing of the cross-sections of other processes involving protons and atomic hydrogen to compute a mean specific energy per ion pair in a gas of atomic hydrogen for a beam consisting of protons and neutral hydrogen atoms in charge equilibrium, a range of beam energies from 10 keV to 3 MeV being covered. In contrast to previous theories, capture and loss are taken explicitly into account and it is shown that they cause a considerable extension of the range over which the mean specific energy is nearly constant. The mean specific energy per ion pair is also calculated as a function to impact energy for an electron beam with energies up to 1 keV. The results are in harmony with experimental data if the assumption is made that (at high energies) a hydrogen molecule is equivalent to two hydrogen atoms.