Ultraviolet absorption spectra of the benzyl radical formed during pulse radiolysis

Abstract

Solutions of benzyl chloride and benzyl alcohol in cyclohexane were subjected to pulse radiolysis. The absorption of the band at 307/318 nm (2²A₂ excited state) of the benzyl radical increased with solute concentration as expected over the range from to 10^-5 to 10^-1 M. On the other hand, the absorption of the 258-nm band (4²B₂ state) decreased with concentration and is zero at 10^-2 M. It is considered that the population of radicals in the vibrational or electronic sub-levels of the ground state from which the 4²B₂ transitions take place is affected by an interaction or association process dependent on solute concentration. Extinction coefficients (l. mol^-1 cm^-1) for the benzyl radical in 10^-5 M solution are 9000 at 318 nm, 4500 at 307 nm and 41000 at 258 nm.