CAVITY RINGDOWN SPECTROSCOPY AND KINETICS OF HO$_2$+HCHO: DETECTION OF THE $\nu_1$ AND \ {A}-\ {X} BANDS OF HOCH$_2$OOCAVITY RINGDOWN SPECTROSCOPY AND KINETICS OF HO$_2$+HCHO: DETECTION OF THE $\nu$$_1$ AND \ {A}-\ {X} BANDS OF HOCH$_2$OO
Loading...
Date
2011
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The reactions of HO$_2$ with carbonyl compounds are believed to be a sink for carbonyl compounds in the upper troposphere and lower stratosphere. These reactions proceed through a hydrogen bound intermediate before isomerizing. \textbf{2005}, \textit{109}, 4303.} The reaction of HO$_2$ + formaldehyde (HCHO) serves as a prototype for this class of reactions, forming the isomerization product hydroxymethylperoxy (HOCH$_2$OO, HMP). Previous studies measured the spectrum and kinetics of HMP using either FTIR detection of the end products \textbf{1979}, \textit{83}, 3185.} or direct detection of HMP by the unstructured \~{B}-\~{X} transition. \textbf{1989}, \textit{93}, 2368.}$^{,}$ \textbf{1989}, \textit{93}, 2375} Despite these studies, considerable uncertainty exists in the rate constant of HMP formation (à ±80\%, 2$\sigma$). \textit{Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation Number 16}, Jet Propulsion Laboratory, 2009} In this talk, we report the first detection of the $\nu$$_1$ (OH stretch) and \~{A}-\~{X} electronic spectra of the HMP radical. The OH stretch spectrum is broad and featureless, while the \~{A}(0)-\~{X}(0) origin and combination band with the OOCO torsion \~{A}(\textit{n}$_{OOCO}$=1)-\~{X}(0) are rotationally resolved. Quantum chemistry calculations have been performed on both the \~{A} and \~{X} states as a function of the OOCO and HOCO dihedral angles to estimate the \~{A}-\~{X} transition frequency and to assess the coupling between the two torsional modes. We also present kinetics data showing the rates of production and destruction of HMP. The reactions of HO$_2$ with carbonyl compounds are believed to be a dominant sink for carbonyl compounds in the upper troposphere and lower stratosphere. These reactions proceed through a hydrogen bound intermediate before isomerizing. \textbf{2005}, \textit{109}, 4303.} The reaction of HO$_2$ + formaldehyde (HCHO) serves as a prototype for this class of reactions, forming the isomerization product hydroxymethylperoxy (HOCH$_2$OO, HMP). Previous studies measured the spectrum and kinetics of HMP using either FTIR detection of the end products \textbf{1979}, \textit{83}, 3185.} or direct detection of HMP by the unstructured \~{B}-\~{X} transition. \textbf{1989}, \textit{93}, 2368.}$^{,}$ \textbf{1989}, \textit{93}, 2375} Despite these studies, considerable uncertainty exists in the rate constant of HMP formation (±80\%, 2$\sigma$). \textit{Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation Number 16}, Jet Propulsion Laboratory, 2009} In this talk, we report the first detection of the $\nu$$_1$ (OH stretch) and \~{A}-\~{X} electronic spectra of the HMP radical. The OH stretch spectrum is broad and featureless, while the \~{A}(0)-\~{X}(0) origin and combination band with the OOCO torsion \~{A}(\textit{n}$_{OOCO}$=1)-\~{X}(0) are rotationally resolved. Quantum chemistry calculations have been performed on both the \~{A} and \~{X} states as a function of the OOCO and HOCO dihedral angles to estimate the \~{A}-\~{X} transition frequency and to assess the coupling between the two torsional modes. We also present kinetics data showing the rates of production and destruction of HMP.
Description
Author Institution: California Institute of Technology, Division; of Chemistry, MC 127-72, Pasadena, CA 91125; Jet Propulsion Laboratory; California Institute of Technology, MS 183-901, Pasadena, CA 91109; California Institute of Technology, Division of Chemistry, MC 127-72, Pasadena, CA 91125; NASA Jet Propulsion Laboratory, MS 183-901, Pasadena, CA 91109