Photoelectron–photofragment coincidence studies of the dissociative photodetachment of O4−

Abstract

The dissociative photodetachment dynamics of O4− (O4−+hν→O2+O2+e−) have been studied at 532, 355, and 266 nm by triple-coincidence measurements of the energy and angular distributions of the photoelectron and photofragments. The data reveal vibrationally resolved product translational energy distributions and a strong angular correlation between the photoelectron and the photofragments for this direct process. The translational energy distributions show that photodetachment of O4− over this photon energy range occurs to several low-lying repulsive states of O4, producing O2 in the ground and low-lying electronically excited states (O2(X 3Σ−g), O2(a 1Δg), and O2(b 1Σ+g)). The partitioning of energy into vibration and rotation of the O2 products is analyzed in terms of a Franck–Condon model, indicating that the excess electron in O4− is delocalized over two identical O2 moieties in a symmetric O4− species. A qualitative analysis of the product angular distributions in terms of the electronic structure of O4− is consistent with recent ab initio calculations.