Role of OH radicals in the formation of oxygen molecules following vacuum ultraviolet photodissociation of amorphous solid water

Photodesorption of O2(X 3Σg-) and O2(a 1Δg) from amorphous solid water at 90 K has been studied following photoexcitation within the first absorption band at 157 nm. Time-of-flight and rotational spectra of O2 reveal the translational and internal energy distributions, from which production mechanisms are deduced. Exothermic and endothermic reactions of OH+O(3P) are proposed as plausible formation mechanisms for O2(X 3Σg- and a 1Δg). To examine the contribution of the O(3P)+O(3P) recombination reaction to the O2 formation following 157 nm photolysis of amorphous solid water, O2 products following 193 nm photodissociation of SO2 adsorbed on amorphous solid water were also investigated.