Balmer emission induced by proton impact on atomic hydrogen

Abstract

The semiclassical two-centre convergent-close-coupling approach is applied to study Balmer emission in proton-hydrogen scattering at the incident proton energies from 5–1 MeV. The approach uses wave-packet pseudostates for the discretization of the continuous spectrum of the hydrogen atom, constructed from the Coulomb wave function. All cross sections for target excitation into the final states with principal quantum numbers n = 3 and 4 required for obtaining the Balmer emission cross sections, polarisation fraction and Balmer decrement are calculated. Corresponding electron-capture cross sections are also given. A substantial variation in the cross sections for population of magnetic sublevels obtained in different theoretical approaches is found. The present cross section for excitation of the n = 3 shell as a whole does not agree with experiment, but supports earlier calculations. At the same time, the individual cross section for excitation of the 3p state displays excellent agreement with available experimental measurements. The results for polarisation fraction of the Balmer-α emission significantly disagree with experimental measurements at high energies. The calculated Balmer decrement plateaus at about 100 keV and can be used in astrophysical applications.