Mechanisms for O-2 dissociation during pulsed-laser ablation and deposition

We investigate different dissociation mechanisms for O-2 gas during pulsed- laser ablation and deposition. Mesaurements are carried out by using an in situ diagnostics based on absorption spectroscopy of oxygen gas, with space - and time-resolved capabilities, during laser ablation of a metal alloy ta rget in the presence of an oxygen environment. Data, analyzed as a function of ablation parameters, indicate that two different mechanisms, involving electron collisions and formation of a high-density, high-temperature shock layer, play an important role in producing atomic oxygen which can subsequ ently react with the ablated species. (C) 2001 American Institute of Physic s.