Photo-double-ionization of He-like and Be-like systems in excited states within an intermediate-energyR-matrix framework

Abstract

In this article we apply the intermediate-energy $R$-matrix method to photo-double-ionization of the metastable $1s2s{\phantom{\rule{4pt}{0ex}}}^{1,3}{S}^{e}$ and $1s2p{\phantom{\rule{4pt}{0ex}}}^{1,3}{P}^{o}$ states of He, ${\mathrm{O}}^{6+}$, and ${\mathrm{Ne}}^{8+}$, along with the $1{s}^{2}\phantom{\rule{4pt}{0ex}}2s2p{\phantom{\rule{4pt}{0ex}}}^{1,3}{P}^{o}$ and $1{s}^{2}\phantom{\rule{4pt}{0ex}}2s3s{\phantom{\rule{4pt}{0ex}}}^{1,3}{S}^{e}$ states of Be, ${\mathrm{O}}^{4+}$, and ${\mathrm{Ne}}^{6+}$. We compare our results with other theoretical data where possible and achieve excellent agreement. We examine trends between the various excited states and ground states of the systems.