OH production from the photolysis of isoprene-derived peroxy radicals: cross-sections, quantum yields and atmospheric implications.

In environments with high concentrations of biogenic volatile organic compounds and low concentrations of nitrogen oxides (NO = NO + NO), significant discrepancies have been found between measured and modeled concentrations of hydroxyl radical (OH). The photolysis of peroxy radicals from isoprene (HO-Iso-O) in the near ultraviolet represents a potential source of OH in these environments, yet has not been considered in atmospheric models. This paper presents measurements of the absorption cross-sections for OH formation (σ) from the photolysis of HO-Iso-O at wavelengths from 310-362.

Direct evidence for a substantive reaction between the Criegee intermediate, CH2OO, and the water vapour dimer.

The C1 Criegee intermediate, CH2OO, reaction with water vapour has been studied. The removal rate constant shows a quadratic dependence on [H2O], implying reaction with the water dimer, (H2O)2. The rate constant, kCH2OO+(H2O)2 = (4.