Valence-shell double photoionization of alkaline-earth-metal atoms

Abstract

We apply the convergent close-coupling formalism to describe direct double photoionization (DPI) of the valence $n{s}^{2}$ shell of alkaline-earth-metal atoms: beryllium $(n=2)$, magnesium $(n=3)$, and calcium $(n=4)$. We consider the range of photon energies below the onset of resonant and Auger ionization processes where the subvalent and core electrons can be treated as spectators. By comparing alkaline-earth-metal atoms with helium, we elucidate the role of the ground state and final ionized state correlations in DPI of various quasi-two-electron atoms.