Absolute Single Photoionization Cross-Section Measurements of Br⁺

Absolute single photoionization cross-section measurements of Br⁺ ions were performed using the photo-ion, merged-beams technique with synchrotron radiation at the Advanced Light Source at Lawrence Berkeley National Laboratory. Measurements of Br⁺ were made in the photon energy range 17.0 eV to 32.5 eV with a photon energy resolution of 29.2 meV. These measurements span the ³P₂ ground state ionization threshold as well as the ³P₁, ³P₀, ¹D₂, ¹S₀ metastable state ionization thresholds. We identified multiple Rydberg resonance series in the auto-ionization resonance structure of Br⁺ and used these identifications to verify the reported ionization potential of Br⁺ and accurately determine the excited-state energy levels of low-lying metastable states of both Br⁺ and Br²⁺. The ionization potential of Br⁺ and the metastable-state energy levels were found to agree with the tabulated energy levels reported by NIST to within the energy uncertainties of the NIST values and the present measurements. The measurements are also compared to Breit-Pauli R-matrix calculations with positive agreement between theory and experiment.