Destruction of fast metastable hydrogen atoms passing through atomic helium

Abstract

The first Born approximation is used to calculate cross sections for excitation or de-excitation to discrete states from fast metastable hydrogen atoms passing through atomic helium. Full account is taken of double transitions and the calculations are performed using length and velocity formulation values of the Born helium matrix elements. Close coupling values in the impact parameter theory for the specific transitions 2s to nl(nl=1s, 2p, 3s, 3p) in hydrogen with the target helium atom unexcited indicate that coupling to excited states and to the hydrogen continuum is not important for these particular destruction processes for impact energies greater than 10 keV. Addition of the present Born approximation results to those of Bell and Kingston (1971) for the electron loss contribution provide total destruction cross sections which are a factor of about 2.5 lower than the experimental data (5-30 keV) of Gilbody et al (1971). For electron loss, the recent data of Hughes and Choe suggests that the first Born approximation may be satisfactory for impact energies greater than 100 keV.