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

Abstract

The gas phase absolute UV absorption cross sections at 213.9 nm for CH 3 OOH, H 2 O 2 , and D 2 O 2 have been determined to be (22.51±0.78) × 10 −20 , (33.04±2.17) × 10 −20 , and (35.37±4.25) × 10 −20 cm 2 molecule −1 , respectively, at 297±1 K. The corresponding values at 253.7 nm for H 2 O 2 and D 2 O 2 were (7.37±0.31) × 10 −20 and (7.86±1.04) × 10 −20 cm 2 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 Fe 2+ or I − solutions. The relative cross sections for CH 3 OOH and H 2 O 2 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.