Observation of the Ã−X̃ Electronic Transition of the β-Hydroxyethylperoxy Radical

The Ã−X̃ electronic absorption spectrum of β-hydroxyethyl peroxy radical (β-HEP) has been recorded in the NIR by cavity ringdown spectroscopy. The precursor, β-hydroxyethyl radical, is generated by photolysis of 2-iodoethanol and by OH-initiated oxidation of ethene, in both cases followed by addition of O2 to form the peroxy. Although electronic structure calculations predict that 13 conformers of β-HEP exist as minima on the potential energy surface, the experimental spectrum is rationalized in terms of the band origins and vibrational progressions of only the two most stable conformers, G1G2G3 and G1 ′G2G3.