Polarization studies of H(2p) charge-exchange excitation: H+-Ar collisions.

Alignment and orientation for H(2p) excitation in ${\mathrm{H}}^{+}$-Ar collisions have been measured for incident proton energies of 1.5 and 3 keV, and in the range of scattering angles between 0.5\ifmmode^\circ\else\textdegree\fi{} and 3.5\ifmmode^\circ\else\textdegree\fi{}. From the experimental results the relative population of magnetic substates H(2${p}_{0}$) and H(2${p}_{\ifmmode\pm\else\textpm\fi{}1}$) is extracted. The observed magnitude of the H(2${p}_{0}$) excitation suggests that, in addition to a 3d\ensuremath{\sigma}-3d\ensuremath{\pi} rotational coupling, a 3d\ensuremath{\sigma}-4p\ensuremath{\sigma} radial coupling is effective.