Electron loss and de-excitation of 5-500 keV metastable hydrogen atoms in passage through gas targets

Abstract

The collisional destruction of 5-500 keV 2s metastable hydrogen atoms in passage through H2, He, Ar, Kr and N2 has been investigated using a modulated beam technique. Cross sections sigma 2s.1 for one-electron loss and total cross sections sigma D for all collisional destruction processes have been separately determined. Electron capture leading to negative ion formation is found to be relatively unlikely at the highest energies considered sigma 2s.1 approximately= sigma D. Cross sections for de-excitation sigma 2s.1s approximately=( sigma D- sigma 2s.1) increase in relative importance with decreasing impact energy. Values of both sigma 2s.1s and sigma D for H2 and He agree with estimates based on the first Born approximation. The growth and equilibration of H(2s) atoms in electron capture by protons in H2, He, Ar and N2 has also been investigated and interpreted quantitatively in terms of the relevant collision mechanisms.