Valence-shell photoabsorption spectra of C, Si, Ge, and Sn

We present the results of R-matrix calculations for the bound-state properties of the atoms in the carbon group for states with odd parity and J=0–3. The calculations were performed in LS coupling with the fine-structure interaction incorporated through an LS-jj frame transformation. We also present the photoionization cross section of the ${\mathit{ns}}^2$ ${\mathit{np}}^2$ ${}_{}{}^3{}_{}{}^{}$ ${\mathit{P}}_0$ ground state for each of the atoms for final-state energies between the two ${\mathit{ns}}^2$np ${}_{}{}^2{}_{}{}^{}$ ${\mathit{P}}_{\mathit{J}\mathit{c}}^{\mathit{o}}$ spin-orbit split thresholds. We discuss some of the limitations of our method.