An R-matrix with pseudo-state approach to the single photon double ionization and excitation of the He-like Li+ ion

Abstract

The success of the R-matrix with pseudo-state (RMPS) method to model single photoionization processes, benchmarked against dedicated synchrotron light source measurements, is exploited and extended to investigate, single photon double ionization cross-sections for the He-like, Li+ ion. We investigate these processes from both the ground state and the excited 1s2s 1, 3S metastable levels of this He-like system. Comparisons of the results from the RMPS method are made with other state-of-the-art theoretical approaches such as time-dependent close-coupling (TDCC), B-splines and the convergent close-coupling (CCC). Excellent agreement with various other theoretical approaches are achieved but differences occur which are highlighted and discussed. For the ground state the peak of the cross-section is ∼2 kilo-barns (Kb), that for the 1s2s 1S state is ∼6 and ∼1 Kb for the corresponding 1s2s 3S state. All the cross-sections for single photon double ionization are extremely small, being in the region of 2–10 Kb, or less, rendering their experimental determination extremely challenging.