Photoionization cross sections of the aluminumlike Si + ion in the region of the 2p threshold (94-137 eV)

We present measurements of the absolute photoionization cross section of the aluminumlike Si + ion over the 94–137 eV photon energy range. The measurements were performed using the merged-beam setup on the PLEIADES beamline at the SOLEIL synchrotron radiation facility. Signals produced in the Si 2+ and Si 3+ photoionization channels of the 2p subshell of the Si + ion from both the 1s 2 2s 2 2p 6 3s 2 3p 2 P1/2,3/2 ground levels and the 1s 2 2s 2 2p 6 3s3p 24 P metastable levels were observed. Absolute cross sections were determined. Calculations of the 2p inner-shell photoionization cross sections were carried out using the multiconfiguration Dirac-Fock and Dirac-Coulomb R-matrix theoretical approaches and are compared with experiment.