title: VUV photoionization cross sections of HO2, H2O2, and H2CO.
abstract: The absolute vacuum ultraviolet (VUV) photoionization spectra of the hydroperoxyl radical (HO2), hydrogen peroxide (H2O2), and formaldehyde (H2CO) have been measured from their first ionization thresholds to 12.008 eV. HO2, H2O2, and H2CO were generated from the oxidation of methanol initiated by pulsed-laser-photolysis of Cl2 in a low-pressure slow flow reactor. Reactants, intermediates, and products were detected by time-resolved multiplexed synchrotron photoionization mass spectrometry. Absolute concentrations were obtained from the time-dependent photoion signals by modeling the kinetics of the methanol oxidation chemistry. Photoionization cross sections were determined at several photon energies relative to the cross section of methanol, which was in turn determined relative to that of propene. These measurements were used to place relative photoionization spectra of HO2, H2O2, and H2CO on an absolute scale, resulting in absolute photoionization spectra.
authors.affiliation: Division of Chemistry and Chemical Engineering and §NASA Jet Propulsion Laboratory, California Institute of Technology , Pasadena, California 91125, United States.
authors.forename: Leah G
authors.initials: LG
authors.lastname: Dodson
authors.forename: Linhan
authors.initials: L
authors.lastname: Shen
authors.forename: John D
authors.initials: JD
authors.lastname: Savee
authors.forename: Nathan C
authors.initials: NC
authors.lastname: Eddingsaas
authors.forename: Oliver
authors.initials: O
authors.lastname: Welz
authors.forename: Craig A
authors.initials: CA
authors.lastname: Taatjes
authors.forename: David L
authors.initials: DL
authors.lastname: Osborn
authors.forename: Stanley P
authors.initials: SP
authors.lastname: Sander
authors.forename: Mitchio
authors.initials: M
authors.lastname: Okumura