Photoelectron spectroscopy of O- at 266 nm: Ratio of ground- and excited-state atomic oxygen production and channel-resolved photoelectron anisotropy parameters

The photodetachment dynamics of the atomic oxygen anion O- has been investigated at 266 nm (4.67 eV) by photoelectron detection in a crossed-beam experiment using a magnetic-bottle electron spectrometer. Taking explicit advantage of the Doppler shift imposed by the moving ion beam on the photoelectron energies, we report both the final-state branching ratio and photoelectron angular distributions. After photoabsorption at 266 nm, the formed electron-oxygen scattering state disintegrates, forming either the excited D-1 or the ground P-3 state of oxygen with a partition of D-1:P-3 = 0.32 +/- 0.06. The detachment leading to the production of O(P-3) shows an angular distribution of photoelectrons characterized by beta(P) = 0.00 +/- 0.10 mimicking a pure s-wave detachment, while the detachment into excited O(D-1) occurs with beta(D) = -0.90 +/- 0.10, giving direct evidence of interference between the outgoing s and d waves.