title: Infrared action spectroscopy and dissociation dynamics of the HOOO radical.
abstract: The HOOO radical has long been postulated to be an important intermediate in atmospherically relevant reactions and was recently deemed a significant sink for OH radicals in the tropopause region. In the present experiments, HOOO radicals are generated in a pulsed supersonic expansion by the association of O(2) and photolytically generated OH radicals, and the spectral signature and vibrational predissociation dynamics are investigated via IR action spectroscopy, an IR-UV double resonance technique. Rotationally resolved IR action spectra are obtained for trans-HOOO in the fundamental (nu(OH)) and overtone (2nu(OH)) OH stretching regions at 3569.30 and 6974.18 cm(-1), respectively. The IR spectra exhibit homogeneous line broadening, characteristic of a approximately 26-ps lifetime, which is attributed to intramolecular vibrational redistribution and/or predissociation to OH and O2 products. In addition, an unstructured feature is observed in both the OH fundamental and overtone regions of HOOO, which is likely due to cis-HOOO. The nascent OH X(2)Pi, v = 0 or v = 1, products following vibrational predissociation of HOOO, nu(OH) or 2nu(OH), respectively, have been investigated using saturated laser-induced fluorescence measurements. A distinct preference for population of Pi(A') Lambda-doublets in OH was observed and is indicative of a planar dissociation of trans-HOOO in which the symmetry of the bonding orbital is maintained.
authors.affiliation: Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA.
authors.forename: Erika L
authors.initials: EL
authors.lastname: Derro
authors.forename: Craig
authors.initials: C
authors.lastname: Murray
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Sechler
authors.forename: Marsha I
authors.initials: MI
authors.lastname: Lester
mesh_terms: D005609:Free Radicals; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013816:Thermodynamics
chemical_list: D005609:Free Radicals