Experimental Photoionization Cross-Section Measurements in the Ground and Metastable State Threshold Region of Se +

Absolute photoionization cross-section measurements are reported for Se+ in the photon energy range 18.0–31.0 eV, which spans the ionization thresholds of the 4S3/2 ground state and the low-lying 2P3/2, 1/2 and 2D5/2, 3/2 metastable states. The measurements were performed using the Advanced Light Source synchrotron radiation facility. Strong photoexcitation–autoionization resonances due to 4p → nd transitions are seen in the cross-section spectrum and identified with a quantum-defect analysis.