Ozonoylsis of alkenes in the troposphere results in Criegee intermediates, which have eluded detection in the gas phase until very recently.[Wetz et al. Science 335, 204 (2012)]  This laboratory has synthesized the simplest Criegee intermediate within a quartz capillary tube affixed to a pulsed valve to cool and isolate CH2OO in a supersonic expansion.  UV excitation resonant with the B 1A' - X 1A' transition depletes the ground state population of CH2OO, which is detected by single-photon ionization at 118 nm on m/z=46.  The large UV-induced depletion (approaching 100%) near the peak of the profile at 320-340 nm is indicative of rapid photodissociation, consistent with a repulsive B 1A' potential along the O-O coordinate computed theoretically (CASSCF).  The experimental spectrum is in good accord with the absorption spectrum calculated using the one-dimensional reflection principle.  The B-X spectrum is combined with the solar actinic flux to estimate the atmospheric lifetime of CH2OO from photodissociation.

Ultraviolet spectrum and photochemistry of the simplest Criegee intermediate CH<sub>2</sub>OO

245th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.

Ultraviolet spectrum and photochemistry of the simplest Criegee intermediate CH2OO

Ultraviolet spectrum and photochemistry of the simplest Criegee intermediate CH₂OO