L-shell photoionization of Ar+ to Ar3+ ions

Absolute photoionization cross sections of Ar+, Ar2+, and Ar3+ ions have been measured in the 250-280 eV photon energy range. These results are compared to theoretical cross sections extracted from two new calculations we performed. They reproduce well the general behavior of the experimental spectra and the magnitude of the direct photoionization cross sections. However, the oscillator strength of the resonant structure in the spectra, dominated by 2p → 3d transitions, is overestimated up to 80% by our calculations. (authors)