15min:

MATTHEW K. SPRAGUE, MITCHIO OKUMURA, California Institute of Technology, Division of Chemistry, MC 127-72, Pasadena, CA 91125; AND STANLEY P. SANDER, Jet Propulsion Laboratory, California Institute of Technology, MS 183-901, Pasadena, CA 91109.

The reactions of HO₂ 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.\footnoteI.~Hermans, J.~F.~Muller, T.~L.~Nguyen, P.~A.~Jacobs, and J.~Peeters. J.~Phys.~Chem.~A \textbf2005, 109 , 4303. The reaction of HO₂ + formaldehyde (HCHO) serves as a prototype for this class of reactions, forming the isomerization product hydroxymethylperoxy (HOCH₂OO, HMP). Previous studies measured the spectrum and kinetics of HMP using either FTIR detection of the end products\footnote F.~Su, J.~G.~Calvert, and J.~H.~Shaw J.~Phys.~Chem. \textbf1979, 83 , 3185. or direct detection of HMP by the unstructured B-X transition.\footnoteB.~Veyret, R.~Lesclaux, M.~T.~Rayez, J.~C.~Rayez, R.~A.~Cox, and G.~K.~Moortgat J.~Phys.~Chem. \textbf1989, 93 , 2368.^,\footnoteJ.~P.~Burrows, G.~K.~Moortgat, G.~S.~Tyndall, R.~A.~Cox, M.~E.~Jenkin, G.~D.~Hayman, and B.~Veyret J.~Phys.~Chem. \textbf1989, 93 , 2375 Despite these studies, considerable uncertainty exists in the rate constant of HMP formation (±80%, 2 ).

In this talk, we report the first detection of the ₁ (OH stretch) and Ã-X electronic spectra of the HMP radical. The OH stretch spectrum is broad and featureless, while the Ã(0)-X(0) origin and combination band with the OOCO torsion Ã( n _OOCO=1)-X(0) are rotationally resolved. Quantum chemistry calculations have been performed on both the à and X states as a function of the OOCO and HOCO dihedral angles to estimate the Ã-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.