Early time detection of OH radical products from energized Criegee intermediates CH2OO and CH3CHOO

The OH radical products from unimolecular decay of energized CH2OO and CH3CHOO Criegee intermediates are detected by laser-induced fluorescence shortly after they are formed utilizing 248 nm photolysis of diiodo precursors and subsequent reaction with O2. The OH radicals from both CH2OO and CH3CHOO are produced with average rotational energies of ∼1–2 kcal mol−1. A different mechanism for unimolecular decay of CH3CHOO is evident from noticeably broader OH A-X (1,0) line profiles, which is attributed to Doppler broadening. Modeling of the Doppler profiles suggests that most of the available energy is channeled into translational excitation of the products.