Relativistic R-matrix studies of photoionization processes of Ar⁵⁺

The 3s–np photoionization processes of the ground state ²P_1/2 and the metastable state ²P_3/2 of Ar⁵⁺ are investigated using our recently developed relativistic R-matrix code, where the interactions between the bound states and the continuum states are included. Both resonance positions and the oscillator strengths are in much better agreement with the absolute experimental measurements by Wang et al.Wang J C, Lu M, Esteves D, Habibi M, Alna’washi G and Phaneuf R A 2007 Phys. Rev. A 75 062712 with a resolution of 80 meV than their theoretical results. The contributions of the two experimental unresolved transitions are distinguished in our calculations, which show that the transitions from the ground state also make significant contributions to some resonances. Our theoretical results are also in good agreement with the measurements for the first resonance with a higher resolution of 20 meV.