Quantum yields for the photolysis of glyoxal below 350 nm and parameterisations for its photolysis rate in the troposphere

Abstract

The formation of HCO and of H in the photolysis of glyoxal have been investigated over the wavelength ranges 310–335 nm for HCO and 193–340 nm for H. Dye laser photolysis was coupled with cavity ring-down spectroscopy for HCO, and with laser induced fluorescence spectroscopy for H. Absolute quantum yields were determined using actinometers based on (a) Cl₂ photolysis and the Cl + HCHO reaction for HCO and (b) N₂O photolysis (and O¹D + H₂) and CH₂CO photolysis (and CH₂ + O₂) for H. The quantum yields were found to be pressure independent in this wavelength region. Quantum yields for all product channels under atmospheric conditions were calculated and compared with literature values. Differences between this work and previously published work and their atmospheric implications are discussed.