Single-, two- and three VUV photon reactions of a series of alkylarenes in the gas phase

A series of alkylarenes (AR) was excited by an ArF excimer laser in the gas phase. The neutral radical was observed by transient absorption spectroscopy without traces of emission, triplet state, or cation radical. Single and multiphoton (up to three-photon) processes were observed even though molecules have similar structures. This presents a quite different feature from ordinary photochemistry in the condensed phase. Neutral radical production was explained well by the hot molecule mechanism and compared with statistical reaction theory. The differences between multiphoton reactions in the condensed phase and those in the gas phase were discussed.