Photoionization cross section of SiII from threshold to 1 keV

The techniques of many-body perturbation theory with interacting resonances are used to calculate the photoionization cross section of SiII from threshold to 1 keV. The Rayleigh-Schrödinger expansion with $\mathrm{LS}$ coupled states and the Brueckner-Goldstone expansion are compared. Correlations among the $2p$, $3s$, and $3p$ electrons are shown to have a large effect on the cross section. Resonances from $3s 3p \mathrm{np}$, $2p^{5}3s^{2}3p \mathrm{ns}$, $2p^{5}3s^{2}3p \mathrm{nd}$, and $2s 2p^{6}3s^{2}3p \mathrm{np}$ configurations are included.