Electron Capture Process in Collisions of Proton with Excited State of Helium

Total and state-selective cross sections for single electron capture (SEC) from the n = 2 excited state of helium colliding by protons are calculated in the energy range of 1.0-100.0 keV/u by using the two-center atomic orbital close-coupling method. The interaction of the active electron with helium ion is represented by a model potential. Total SEC cross sections show a monotonic decreasing trend with increasing collision energy, and display a different behavior compared with the case from the ground state of helium. It is also found that the dominant reaction channel is captured to the H(2p) state up to 40 keV/u, and then the capture to the H(1s) or H(2s) state becomes more pronounced. Moreover, the alignment dependence on the initial states is obtained for the electron capture from He(2p(0)) and He (2p(1)).