ANGULAR-CORRELATION BETWEEN AUTO-IONIZATION ELECTRONS AND SCATTERED IONS IN 2000-EV HE+-HE COLLISIONS

Complex population amplitudes for the excitation of magnetic sublevels of He(2p2)D1 and He(2s2p)P1 states in 2-keV He+ -He collisions have been determined by measuring the energy spectra of the corresponding autoionization electrons ejected at different angles in coincidence with the inelastically scattered ions. It was found that He(2p2)D1 is excited with a relative probability of 97%. If the direction of the internuclear line at the distance of closest approach is taken as z axis, we find that primarily the m=0 sublevel is populated and that the complete D1 excitation can be interpreted as due to pure m=0 excitations with respect to momentary internuclear lines at different points of the trajectory which are symmetric to the turning point. These results are discussed within the framework of the Fano-Lichten promotion model. Quantization along an axis perpendicular to the scattering plane shows an orientation of the excited D1 state. From this we find that the angular momentum Ly transferred from the motion of the heavy particles to the electron cloud has an expectation value of Ly-. © 1979 The American Physical Society.