Breit-Pauli R-matrix calculation of the 3p photoabsorption of singly ionized chromium

The 3p photoabsorption spectrum of singly ionized chromium has been studied experimentally by Costello et al and theoretically by Dolmatov. However, while both of these methods produce similar resonance positions and classifications, the background cross sections obtained by these two investigations differ considerably. In the present paper a Breit-Pauli R-matrix method has been employed to study the energy region which includes the 3p --> 3d giant resonance. Excellent agreement is found in the 40-46 eV energy region with the positions and classifications of the resonances reported by Costello et al but, in agreement with Dolmatov, the background cross section suggests that further experimental investigation is required. The present work also identifies several further resonances in this region and a more detailed structure is found in the 46-56 eV energy region than in previous studies.