Charge-scaling law for angular correlation in double photoionization of ions and atoms with two active electrons

Abstract

Single-photon double ionization of He, ${\mathrm{Li}}^{+}$, ${\mathrm{Be}}^{2+}$, and ${\mathrm{H}}^{\ensuremath{-}}$, as well as the $K$ shell of neutral Li and Be atoms with ``hollow ion'' formation, is studied using the ab initio time-dependent scaling method that has an advantage of avoiding the explicit use of double continuum correlated functions and allows one to obtain complete information about the threefold differential cross section in a large range of the incident photon energies in a single calculation. It is shown that the dependence of the Gaussian width parameter, that characterizes the angular distribution of threefold differential cross section, on the photon energy exhibits an approximate charge scaling law for angular distribution. The energy values, at which the angular distributions for different targets are similar to those of helium atom, are found. An intriguing violation of Wannier threshold law for hydrogen negative ion is observed.