Angular distribution of autoionization electrons and sublevel population in low energy He+-He collisions

The recent theory of Cleff and Mehlhorn (1974) on the angular distribution of Auger electrons is applied to explain the angular distribution of electrons ejected by autoionization of the 2p 1 1 D state of helium, as observed in He + -He collisions at 15 keV. The unequal populations of the 1 D magnetic sublevels are explained by a quasi-molecular excitation mechanism; the population of the sublevels mod M L mod =1 and M L =0 is ascribed to a rotational coupling at large internuclear distance.