Autoionizing resonances in the photoionization of groundstate atomic magnesium

Abstract

Photoionization of the ground state 1s22s22p63s2 1S ofatomic magnesium is studied theoretically in the energy regionbetween the Mg+(3s) and Mg+(4p) thresholds usingthe non-iterative variational R-matrix method combined withmultichannel quantum defect theory at the R-matrix surface. Theinitial and final states are represented byconfiguration-interaction wavefunctions. We calculated totaland partial photoionization cross sections in both length andvelocity formulations. Photoionization cross sections aredominated by Rydberg series of autoionization resonancesconverging to Mg+(3p, 4s, 3d and 4p) thresholds. We alsocalculated the photoelectron angular distribution asymmetryparameter β for the process leaving the ion in theMg+(3p) state. The present photoionization cross sections arein good agreement with available experiments and previouscalculations. There is excellent agreement between length andvelocity gauges in our calculation.