Absorption cross sections of CH3OOH, H2O2, and D2O2 vapors between 210 and 365 nm at 297 K

The gas phase absolute UV absorption cross sections at 213.9 nm for CH₃OOH, H₂O₂, and D₂O₂ have been determined to be (22.51±0.78) × 10^-20, (33.04±2.17) × 10^-20, and (35.37±4.25) × 10^-20 cm² molecule^-1, respectively, at 297±1 K. The corresponding values at 253.7 nm for H₂O₂ and D₂O₂ were (7.37±0.31) × 10^-20 and (7.86±1.04) × 10^-20 cm² molecule^-1. The UV absorbance of a slowly flowing mixture of peroxide and helium carrier gas in a Pyrex absorption cell was measured, followed by collection and titration of the eluting peroxide with Fe²⁺ or I^- solutions. The relative cross sections for CH₃OOH and H₂O₂ at 298.1, 326.1, 340.4, and 361.1 nm were also determined, using the absolute values at 213.9 nm. The absorption spectra of these peroxides were recorded in the wavelength region between 210 and 365 nm, using a diode array spectrometer, and normalized to the above cross sections to obtain absolute values for the UV absorption cross sections over this entire wavelength region. The obtained results are compared to those from previous investigations. The atmospheric relevance of our measured cross sections is discussed.