Analytical expressions for excitation and ionization cross-sections and rate coefficients of hydrogen-like ions by electron and proton impact

Abstract

Excitation and ionization cross-sections in the Bethe-Born approximation have been computed for a model of the hydrogen-like ion consisting of seven discrete energy levels and a continuum. We propose an interpolation formula connecting the high energy behaviour (Bethe-Born) of the cross-sections and their values at threshold (Coulomb-Born I). We compare this formula with other—frequently used—formulae. Excitation and ionization rate coefficients in a Maxwellian plasma have been computed.