Open AccessThe importance of weak absorption features in promoting tropospheric radical production
Author(s) -
Jamie Matthews,
Amitabha Sinha,
Joseph S. Francisco
Publication year - 2005
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0502687102
Subject(s) - troposphere , absorption (acoustics) , photochemistry , atmosphere (unit) , flux (metallurgy) , atmospheric chemistry , atmospheric sciences , environmental science , chemistry , radical , chemical physics , ozone , meteorology , physics , optics , organic chemistry
Atmospheric field measurement and modeling studies have long noted discrepancies between observation and predictions of OH and HO(2) concentrations in the atmosphere. Novel photochemical mechanisms have been proposed to explain these differences. Although inclusion of these additional sources improves agreement, they are unable to fully account for the observations. We report and demonstrate the importance of weak electronic absorption features, normally ignored or not measured, in contributing to significant OH radical production. Experiments on methyl hydroperoxide, a prototypical organic peroxide in large abundance in the troposphere, highlights how photochemistry in the neglected electronic absorption tail makes an important addition to the tropospheric OH budget. The present results underscore the need to measure absorption cross sections for atmospheric molecules over a wider dynamic range, especially over the wavelength regions where the solar flux is high, to fully quantitate their contributions to atmospheric photochemistry.