Laser-induced fluorescence, dispersed fluorescence and lifetime measurements of jet-cooled chloro-substituted benzyl radicals

We measured the laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of jet-cooled -, o- and m-chlorobenzyl radicals after they were generated by the 193 nm photolysis of the corresponding parent molecules. The vibronically resolved spectra were obtained to analyze their D₁–D₀ transitions. The fluorescence lifetimes of -, o-, m- and p-chlorobenzyls in the zeroth vibrational levels of the D₁ states were measured to estimate the oscillator strengths of a series of benzyl derivatives. It was found that the -substitution is inefficient to break the ‘accidental forbiddenness' of the D₁–D₀ transition of benzyl, while the ring-substitution enhances the oscillator strength by 50%.