High-resolution velocity-map-imaging photoelectron spectroscopy of the O− photodetachment fine-structure transitions

A high-resolution photoelectron velocity-map-imaging study is reported for the photodetachment of the atomic oxygen anion at 5320.3em0exnm, where five of the six possible spin-orbit fine-structure transitions have been resolved. A resolution of ΔE∕E=0.38% was achieved. Within the experimental uncertainty, each of the fine-structure transitions has the same anisotropy, the averaged β=-0.89(1) consistent with previous, fine-structure-unresolved, experimental and theoretical determinations.