260 Ab Initio Energies and Product Branching Ratios for the O + HCO Reaction

Thursday, November 5, 2009: 4:20 PM
Kohlberg (Camino Real Hotel)
Gary D. DeBoer , Chemistry and Physics, LeTourneau University, Longview, TX, Longview, TX
George L. Barnes , Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
Kyoyeon Park , Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
William L. Hase , Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
Jennifer L. Gardner , US Air Force Research Lab, Hanscom AFB, MA
James A. Dodd , Space Vehicles Directorate, Air Force Research Laboratory, Hanscom AFB, MA
The energetics and reaction dynamics of the O(3P) + HCO(X 2A¢) reaction have been investigated using a combination of electronic structure and statistical branching ratio calculations.  Intermediate and transition state structures were calculated for isomers and conformers of the lowest-lying doublet energy surface using determinant based complete active space self-consistent field (CASSCF) and multi-reference perturbation theory (MRPT2) as well as single reference density functional theory (DFT) and second order Møller-Plesset perturbation theory (MP2).  More accurate energies were obtained for the single reference structures based on compound CBS-QB3 and G3 electronic structure calculations.  After characterizing the species energies, geometries, and vibrational frequencies, RRKM unimolecular reaction rate theory was used to predict branching ratios for formation of the H + CO2 and OH + CO reaction products over the 300‑3000 K temperature and 0.001‑760 Torr pressure ranges.  The roles played by various isomers in the reaction dynamics are discussed, including trans-HCOO, HCO2, and cis- and trans-HOCO.