Photoionization studies of the B⁺ valence shell: experiment and theory

We have investigated L-shell photoionization (PI) of ¹S ground-state and ³P^o metastable states of the Be-like ion, B⁺, in the photon energy range 22.4–31.3 eV, at an experimental energy resolution of 25 meV. Absolute PI cross sections have been measured using a photon–ion merged-beams arrangement at the Advanced Light Source. Detailed calculations using the semi-relativistic Breit–Pauli R-matrix approach suggest a fraction of 29% of metastable ions in the primary beam of the experiment. Excellent agreement is observed between the theoretical predictions and the experimental high-resolution PI cross sections. The present results are compared with earlier experimental and theoretical work. The cross section for PI of B⁺ ground-state ions can be very well described by an analytic formula derived from quantum defect theory.