Temperature‐dependent absorption cross sections for hydrogen peroxide vapor

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Abstract
Relative absorption cross sections for hydrogen peroxide vapor were measured over the temperature ranges 285–381 K for 230 nm ≤ λ ≤ 295 nm and 300–381 K for 193 nm ≤ λ ≤ 350 nm. The well‐established 298 K cross sections at 202.6 and 228.8 nm were used as an absolute calibration. A significant temperature dependence was observed at the important tropospheric photolysis wavelengths, λ > 300 nm. Measured cross sections were extrapolated to lower temperatures, using a simple model which attributes the observed temperature dependence to enhanced absorption by molecules possessing one quantum of O–O stretch vibrational excitation. Upper tropospheric photodissociation rates calculated using the extrapolated cross sections are about 25% lower than those calculated using currently recommended 298 K cross sections.