The absolute cross section for L-shell photoionization of C+ ions from threshold to 105 eV

The absolute cross section for photoionization of C+ ions has been measured from the ionization threshold at 24 eV to 105 eV by overlapping an ion bea m with a monochromatized synchrotron-radiation beam from the ASTRID undulat or. The measurements, which are important for astrophysical modeling of, fo r example, stellar atmospheres, have been compared with R-matrix calculatio ns from the Opacity Project and the Iron Project. The general agreement bet ween theory and experiment is good, yet differences in the magnitude of the cross section of up to 50% are observed as well as some deviations concern ing the resonance structure.