Photoelectron angular distributions, cross sections, and branching ratios for atomic oxygen

Theoretical calculations of the angular distribution of photoelectrons ejected from the $2p$ subshell of atomic oxygen for photoelectron kinetic energies $0\le \epsilon \le 30$ Ry are presented using both Hartree-Fock (HF) and Herman-Skillman (HS) wave functions. Owing to the weakness of anisotropic electron-ion interactions, as evidenced by small differences between HF photoelectron phase shifts for alternative outgoing channels, the simple HS calculation of the angular-distribution asymmetry parameter is found to agree to within ≲ 0.1 with the HF calculations. Photoionization cross sections and photoelectron branching ratios have also beem computed in both the HF and HS approximation for the $2p$ subshell of atomic oxygen in the wavelength range $910\le \lambda \le 100$ ÅA. Comparison is made with other theoretical calculations and with the experimental branching-ratio measurements of Samson and Petrosky at $\lambda =584.3\mathrm{}$ ÅA.