Cavity ringdown spectroscopy of the NIR electronic transition of allyl peroxy radical (H2CCH–CH2OO·)

The A ∼ - X ∼ electronic absorption spectrum of allyl peroxy radical has been recorded at room temperature by cavity ringdown spectroscopy. Photolysis of an allyl bromide/ O 2 mixture at 193 nm or 248 nm yields allyl peroxy and HO 2 radicals, with 248 nm photolysis more strongly favoring allyl peroxy formation. Utilizing electronic structure calculations (including computed OOCC torsional potentials), the experimental spectrum is assigned in terms of the three conformers predicted to have the greatest intensity. This work represents an extension of recent progress in measuring A ∼ - X ∼ absorption spectra of saturated organic peroxy radicals to unsaturated species.