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McCarthy MC, Martinez O, McGuire BA, et al. Isotopic studies of trans- and cis-HOCO using rotational spectroscopy: Formation, chemical bonding, and molecular structures. J Chem Phys. 2016;144(12):124304doi: 10.1063/1.4944070.
McCarthy, M. C., Martinez, O., McGuire, B. A., Crabtree, K. N., Martin-Drumel, M. A., & Stanton, J. F. (2016). Isotopic studies of trans- and cis-HOCO using rotational spectroscopy: Formation, chemical bonding, and molecular structures. The Journal of chemical physics, 144(12), 124304. https://doi.org/10.1063/1.4944070
McCarthy, Michael C, et al. "Isotopic studies of trans- and cis-HOCO using rotational spectroscopy: Formation, chemical bonding, and molecular structures." The Journal of chemical physics vol. 144,12 (2016): 124304. doi: https://doi.org/10.1063/1.4944070
McCarthy MC, Martinez O, McGuire BA, Crabtree KN, Martin-Drumel MA, Stanton JF. Isotopic studies of trans- and cis-HOCO using rotational spectroscopy: Formation, chemical bonding, and molecular structures. J Chem Phys. 2016 Mar 28;144(12):124304. doi: 10.1063/1.4944070. PMID: 27036445.
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J Chem Phys. 2016 Mar 28;144(12):124304. doi: 10.1063/1.4944070.

Isotopic studies of trans- and cis-HOCO using rotational spectroscopy: Formation, chemical bonding, and molecular structures.

The Journal of chemical physics

Michael C McCarthy, Oscar Martinez, Brett A McGuire, Kyle N Crabtree, Marie-Aline Martin-Drumel, John F Stanton

Affiliations

  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA and School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, USA.
  2. National Radio Astronomy Observatory, Charlottesville, Virginia 22901, USA.
  3. Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, Texas 78712-0165, USA.

PMID: 27036445 DOI: 10.1063/1.4944070

Abstract

HOCO is an important intermediate in combustion and atmospheric processes because the OH + CO → H + CO2 reaction represents the final step for the production of CO2 in hydrocarbon oxidation, and theoretical studies predict that this reaction proceeds via various intermediates, the most important being this radical. Isotopic investigations of trans- and cis-HOCO have been undertaken using Fourier transform microwave spectroscopy and millimeter-wave double resonance techniques in combination with a supersonic molecular beam discharge source to better understand the formation, chemical bonding, and molecular structures of this radical pair. We find that trans-HOCO can be produced almost equally well from either OH + CO or H + CO2 in our discharge source, but cis-HOCO appears to be roughly two times more abundant when starting from H + CO2. Using isotopically labelled precursors, the OH + C(18)O reaction predominately yields HOC(18)O for both isomers, but H(18)OCO is observed as well, typically at the level of 10%-20% that of HOC(18)O; the opposite propensity is found for the (18)OH + CO reaction. DO + C(18)O yields similar ratios between DOC(18)O and D(18)OCO as those found for OH + C(18)O, suggesting that some fraction of HOCO (or DOCO) may be formed from the back-reaction H + CO2, which, at the high pressure of our gas expansion, can readily occur. The large (13)C Fermi-contact term (aF) for trans- and cis-HO(13)CO implicates significant unpaired electronic density in a σ-type orbital at the carbon atom, in good agreement with theoretical predictions. By correcting the experimental rotational constants for zero-point vibration motion calculated theoretically using second-order vibrational perturbation theory, precise geometrical structures have been derived for both isomers.

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