Alignment Of Photoionization-Produced He+(2P) Between The N = 2 And Levels

A determination of the alignment of He+(2p) between the n = 2 and 3 levels was carried out by measuring the angular distribution of the 304-angstrom fluorescence that follows photoionization with synchrotron radiation. The alignment A(c)0 is related to the cross-section ratio zeta = sigma-2pkd/sigma-2p and thus provides a means of separating the kd and ks partial-wave contributions to the 2p ion production. The partial-cross-section ratio R = sigma-2p/sigma-2s was also determined by measuring the fluorescence signal at the magic angle with and without an external electric field that quenches the 2s ions. With these data a partition of the n = 2 cross section into the partial cross sections sigma-2skp, sigma-2pks, and sigma-2pkd was carried out. The effect of the broad 1(3) autoionizing resonance in these partial cross sections was determined. A comparison with the results of a many-body-perturbation-theory calculation shows good agreement for the alignment, as well as for R, sigma-2skp, and sigma-2pks, but somewhat of a discrepancy for sigma-2pkd