Date of this Version
Physical Review A 84, 013406 (2011); DOI: 10.1103/PhysRevA.84.013406
Absolute single photoionization cross-section measurements for Se+ ions were performed at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory using the photo-ion merged-beams technique. Measurements were made at a photon energy resolution of 5.5 meV from 17.75 to 21.85 eV spanning the 4s24p34So3/2 ground-state ionization threshold and the 2Po3/2,2Po1/2,2Do5/2, and2Do3/2 metastable state thresholds. Extensive analysis of the complex resonant structure in this region identified numerous Rydberg series of resonances and obtained the Se2+ 4s24p2 3P2 and 4s24p2 1S0 state energies. In addition, particular attention was given to removing significant effects in the measurements due to a small percentage of higher-order undulator radiation.