Cavity-enhanced measurements of hydrogen peroxide absorption cross sections from 353 to 410 nm

We report near-ultraviolet and visible absorption cross sections of hydrogen peroxide (H ₂O ₂) using incoherent broad-band cavity-enhanced absorption spectroscopy (IBBCEAS), a recently developed, high-sensitivity technique. The measurements reported here span the range of 353-410 nm and extend published electronic absorption cross sections by 60 nm to absorption cross sections below 1 × 10 ^-23 cm ² molecule ^-1. We have calculated photolysis rate constants for H ₂O ₂ in the lower troposphere at a range of solar zenith angles by combining the new measurements with previously reported data at wavelengths shorter than 350 nm. We predict that photolysis at wavelengths longer than those included in the current JPL recommendation may account for up to 28% of the total hydroxyl radical (OH) production from H ₂O ₂ photolysis under some conditions. Loss of H ₂O ₂ via photolysis may be of the same order of magnitude as reaction with OH and dry deposition in the lower atmosphere; these processes have very different impacts on HO _x loss and regeneration.