K.A. Hanold and R.E. Continetti, "Photoelecton-Photofragment Coincidence Studies of the Dissociative Photodetachment of O4-", Chem. Phys. 239, 493-509 (1998).
The dissociative photodetachment dynamics of O4-(O4-+ hv --> 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(X3 Sigma g-), O2(a1 Delta g), and O2(b1 Sigma g+)). The partitioning of energy into vibration and rotation of the O2 products is analyzed in terms of a Frank-Condon model, indication that the excess electron in O4- is delocalized over two identical O2 moieties in an 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.