Multichannel photoionization of metastable He(2 (3)Se): A complete study of the 3Po resonances between the N=2 and 3 thresholds.

Abstract

An extensive study of the photoionization of metastable He(2 $^{3}$${\mathit{S}}^{\mathit{e}}$) between the N=2 and N=3 thresholds is presented in this paper. We have calculated the partial 1s\ensuremath{\epsilon}p, 2s\ensuremath{\epsilon}p, 2p\ensuremath{\epsilon}s, 2p\ensuremath{\epsilon}d, and total photoionization cross sections, as well as the \ensuremath{\beta} asymmetry parameters that permit one to obtain the differential cross sections. A complete set of resonance parameters for the first twelve $^{3}$${\mathit{P}}^{\mathit{o}}$ doubly excited states is provided. In particular, the partial widths of these resonances are presented. Our results show that this photoionization process leaves preferentially the ${\mathrm{He}}^{+}$ ion in a 2s state and that the resonance structure is much more pronounced than in photoionization from the ground state. Also, the photoelectrons are ejected preferentially in the direction of the polarization axis of the incident radiation field. Electron-correlation properties of the doubly excited states responsible for the resonant peaks observed in the spectra are discussed in detail.