Proton and antiproton impact excitation of H(2s) atom

Abstract

Direct excitations for atomic hydrogen 2s → 3s, 3p, and 3d transitions by proton and antiproton collisions have been investigated by using an impact parameter treatment. The calculations are performed within the impact parameter versions of the first- and second-order Born approximations, as well as the solution of the coupled differential equations arising from the one-center atomic-orbital close-coupling approach. We have considered calculations that allow couplings to the n = 1–5 states (up to g sub-levels) of the target atom as well as others that neglect the effect of all states other than the initial and final states of the target atom. The sensitivity of the cross sections to the sign of the projectile charge as well as the influence of the mechanism of possible electronic transitions allowed by the techniques under consideration have been studied. The calculated cross sections are compared with those obtained by previous calculations.

Positronium formation for positron scattering from metastable hydrogen

“…In recent years, the excitation and ionization processes of metastable hydrogen in 2s state by positron impact and many other scattering processes by electron, proton, and anti-proton impact have attracted considerable interests and abundant phenomena were found. [7][8][9][10] The Ps formation process of the metastable hydrogen has not been extensively investigated so far.…”