Production of projectile 1s2s2p 4P states by transfer-loss in collisions of O5+ and F6+ ions with H2 and He targets

Single differential cross sections for the production of projectile 1s2s2p 4P states by transfer-loss (TL) are computed, within the independent particle model, for collisions of O5+ and F6+ ions with He and H2 targets in the 3-7 au of velocity range. Projectile 1s electron loss from the 1s22s ground state was calculated within a first-order semiclassical approach, while electron transfer to the projectile (1s2s 3S)nl4L states (n ≥ 1) was computed using the continuum distorted wave (CDW) approximation. Calculations showed TL to the n = 2-7 levels to be of the same order and therefore essential. In particular, all higher lying quartet states, due to spin conservation, can only decay by prompt E1-electric dipole transitions to the 1s2s2p 4P state (and to none below it), thus providing a rather simple and efficient cascade feeding mechanism. An upper limit to this contribution was readily established by assuming that all (1s2s 3S)nl4L states dominantly feed the 1s2s2p 4P state. This leads to a strong enhancement of the 1s2s2p 4P TL cross section, particularly for collisions with the H2 target, reducing dramatically the long-standing two orders of magnitude discrepancy between older TL calculations (for n = 2 only) and existing zero-degree Auger projectile electron spectroscopy measurements. (letter to the editor)