Rotationally resolved photodetachment spectrum of OH−, exposed with velocity-map imaging

Abstract

The photodetachment spectrum of OH− has been measured using velocity-map imaging for the detection of photoelectrons. The relative electron kinetic-energy resolution, determined to be (ΔE/E) = 0.5%, resolves individual rotational transitions, including R3(0) that defines the electron affinity. Previously unobserved, N-, O-, S-, T-branch transitions are also revealed. The angular anisotropy parameters in general exhibit values consistent with electron detachment from O−, β ≈ −0.8, except for the S, T branches which are significantly more isotropic, with β ≈ −0.4.