K-Shell Photoabsorption in O, Ne, Mg, Si, and S Ions

We report on new photoabsorption calculations for neutral and ionized elements of importance for X-ray astronomy observations. Within our R-matrix calculations, spectator Auger broadening effects are taken into account by using an optical potential, and core relaxation is included by using pseudoorbitals and a pseudoresonance elimination method. The resultant photoabsorption cross sections are used in modeling of observed spectra from distant sources to predict elemental abundances in the interstellar medium.