EXCITED-STATE DYNAMICS IN CLUSTERS OF OXYGEN

Considerable insights into the dynamics of both ionic (photodissociati on) and neutral (dissociative photodetachment) decomposition pathways of O-4(-) and O-6(-) have been gained using photoelectron and photofra gment translational spectroscopy in a fast-ion beam. The O-4(-) data a t 532 nm reveal a novel process involving sequential photodetachment o f an electron with a near-zero binding energy from photodissociating O -4(-). Studies of O-6(-) at 532 nm reveal that addition of a third O-2 to the O-4(-) core leads to a dramatic change in the photodissociatio n dynamics, producing highly vibrationally excited O-2(-) photofragmen ts not observed in the case of O-4(-). At 355 nm, both O-4(-) and O-6( -) yield vibrationally excited O-2(-) photofragments, as observed by a utodetachment of the nascent O-2(-) (upsilon greater than or equal to 5) --> O-2 + e(-). At 266 nm, photofragment time-of-flight (TOF) measu rements on O-6(-) and O-4(-) show that the dynamics of dissociative ph otodetachment in O-6(-) are only slightly perturbed relative to O-4(-) . The anisotropic product angular distribution previously observed in O-4(-) is observed to persist in the three-body neutral decomposition O-6(-) + h nu--> O-2 + O-2 + O-2 + e(-). The origins of these diverse phenomena in O-4(-) and O-6(-) are discussed.