Excited state dynamics in clusters of oxygen

Abstract

Considerable insights into the dynamics of both ionic (photodissociation) and neutral (dissociative photodetachment) decomposition pathways of O₄^- and O₆^- have been gained using photoelectron and photofragment translational spectroscopy in a fast-ion beam. The O₄^- data at 532 nm reveal a novel process involving sequential photodetachment of an electron with a near-zero binding energy from photodissociating O₄^-. Studies of O₆^- at 532 nm reveal that addition of a third O₂ to the O₄^- core leads to a dramatic change in the photodissociation dynamics, producing highly vibrationally excited O₂^- photofragments not observed in the case of O₄^-. At 355 nm, both O₄^- and O₆^- yield vibrationally excited O₂^- photofragments, as observed by autodetachment of the nascent O₂^- (v5)→O₂+e^-. At 266 nm, photofragment time-of-flight (TOF) measurements on O₆^- and O₄^- show that the dynamics of dissociative photodetachment in O₆^- are only slightly perturbed relative to O₄^-. The anisotropic product angular distribution previously observed in O₄^- is observed to persist in the three-body neutral decomposition O₆^-+hν→O₂+O₂+O₂+e^-. The origins of these diverse phenomena in O₄^- and O₆^- are discussed.