EARLY EVENTS IN RADIATION-CHEMISTRY AND IN PHOTOIONIZATION

Real-time studies of aliphatic and aromatic hydrocarbons by pulse radi olysis and laser photoionization reveal the chemistry of the ionic spe cies in the condensed phase. The occurrence of radical cation reaction s with solvent molecules provides the core mechanism capable of explai ning a wide range of observations in photoionization and radiation che mistry. The study of products and transients in photoionization of aro matic solutes in hydrocarbon and alcohol solvents illustrates several details of this ''high-energy'' chemistry. A reaction pathway involvin g ion-molecule reaction of excited ions is indicated for a series of p olycyclic aromatic hydrocarbons photoionized using intense excimer las er (248 and 308 nm) pulses in hydrocarbon and alcohol solutions. We ha ve found that condensed-phase ion-molecule reactions in radiolysis are ubiquitous and we speculate on their overall role in hydrocarbon radi olysis.