HR: 0800h
AN: A51B-0035    [Abstracts]
TI: UV Cross Sections and Vibrational Overtone Photodissociation Spectra and Analysis of Hydroxymethyl Hydroperoxide
AU: * Roehl, C M
EM: coleen@gps.caltech.edu
AF: California Institute of Technology, Division of Geological and Planetary, Mailcode 150-21, Pasadena, CA 91125 United States
AU: Fry, J L
A51B-0035 AF: California Institute of Technology, Arthur Amos Laboratory of Chemical Physics, Mailcode 127-72, Pasadena, CA 91125 United States
AU: Wennberg, P O
EM: wennberg@gps.caltech.edu
AF: California Institute of Technology, Division of Geological and Planetary, Mailcode 150-21, Pasadena, CA 91125 United States
AU: Matthews, J
EM: jnmatthews@ucsd.edu
AF: University of California, San Diego, Department of Chemistry and Biochemistry, 9500 Gilman Drive, San Diego, CA 92093 United States
AU: Sinha, A
EM: asinha@chem.ucsd.edu
AF: University of California, San Diego, Department of Chemistry and Biochemistry, 9500 Gilman Drive, San Diego, CA 92093 United States
AU: Lane, J R
EM: jlane@alkali.otago.ac.nz
AF: University of Otago, Department of Chemistry, PO Box 56, Dunedin, Airmail New Zealand
AU: Kjaergaard, H G
EM: henrik@alkali.otago.ac.nz
AF: University of Otago, Department of Chemistry, PO Box 56, Dunedin, Airmail New Zealand
AB: Hydroperoxides are important trace constituents of the urban and global atmosphere. They play important roles in oxidation chemistry as both reservoirs and sinks of OH radical and odd oxygen. Organic peroxides are also oxidants in their own right, oxidizing SO₂ in clouds, fogs, or rain, and are believed to have a toxic effects on plants. Although previously known to be formed via gas phase recombination reactions of peroxy radicals (HO₂, RO₂), organic hydroperoxides have recently been observed following the ozonolysis of isoprene and other alkenes in the presence of water. It is thought that these alkene ozonolysis reactions involve the formation of a carbonyl oxide (or Criegee intermediate) which subsequently reacts with water to form peroxide. The smallest stabilized Criegee intermediate, CH₂OO, formed in the ozonolysis of ethene and terminal alkenes, is believed to react with water to form hydroxymethyl hydroperoxide (HOCH₂OOH). In this study, we report measurement of the UV cross sections and vibrational overtone photodissociation spectra of HOCH₂OOH initiated by excitation of the 4νOH and 5νOH overtone bands, in order to evaluate the importance of this process as an atmospheric HOx source. These studies have made use of high-power, frequency tunable photolysis laser systems that are coupled to sensitive measurements of OH radical products using laser-induced fluorescence (LIF). Supplemental HOCH₂OOH spectra obtained by Fourier transform infrared spectroscopy (FTIR) in the OH-stretching fundamental (νOH) and 2νOH regions as well photodissociation spectra of its partially deuterated analog, HOCD₂OOH, have aided in the analysis of the hydroxymethyl hydroperoxide spectra. A one-dimensional vibrational model of each OH chromophore has been constructed using ab initio calculated OH-stretch potential and dipole moment surfaces. Major features in the observed photodissociation spectrum are explained by the convolution of the calculated absorption intensities (determined from the ab initio surface) with quantum yields estimated.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0317 Chemical kinetic and photochemical properties
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005