H

Alignment of H(2p) in H-He, Ne, Ar collisions

“…Other coupled-channel calculations have been performed recently by Ast et al [13]. These authors realized that at intermediate velocities the different electronic processes, for example excitation, ionization or electron capture, are all of the same order of magnitude.…”

“…For such a situation a large set of basic functions is generally required, while 'truncation of even a few channels may lead to serious errors for the calculated cross section' [13]. The optical potential calculations are based on the assumption that the collision time is short compared to typical relaxation times of the involved atomic species [13]; this assumption is certainly questionable at the low velocities where the quasi-molecular aspect of the collision has to be taken into account [19]. The optical potential calculations for H-He, Ne, and Ar collisions are displayed in Figs.…”

“…At the higher end, we are in the regime of intermediate velocities, where the orbiting velocity of the bound H(ls) electron matches the collision velocity; excitation takes places via so-called 'direct' processes at large internuclear separations, resulting in a large transition probability and in a preferred orientation of the excited electronic charge cloud after the collision (propensity rule) [8]. In the two regimes, calculations based on different theoretical models, for example, molecular orbital [9], close-coupling [10][11][12], optical potential [13], and first Born calculations [143 are available to compare our results with.…”