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Cavity Ringdown Spectroscopy of cis-cisHOONO and the HOONO/HONO_2 Branching Ratio in the Reaction OH + NO_2+ M

Bean, Brian D. and Mollner, Andrew K. and Nizkorodov, Sergey A. and Nair, Gautham and Okumura, Mitchio and Sander, Stanley P. and Peterson, Kirk A. and Francisco, Joseph S. (2003) Cavity Ringdown Spectroscopy of cis-cisHOONO and the HOONO/HONO_2 Branching Ratio in the Reaction OH + NO_2+ M. Journal of Physical Chemistry A, 107 (36). pp. 6974-6985. ISSN 1089-5639. doi:10.1021/jp034407c.

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The termolecular association reaction OH + NO_2 + M was studied in a low-pressure discharge flow reactor, and both HONO_2 and HOONO products were detected by infrared cavity ringdown spectroscopy (IR-CRDS). The absorption spectrum of the fundamental ν1 band of the cis-cis isomer of HOONO (pernitrous or peroxynitrous acid) was observed at 3306 cm^(-1), in good agreement with matrix isolation studies and ab initio predictions. The rotational contour of this band was partially resolved at 1 cm^-1 resolution and matched the profile predicted by ab initio calculations. The integrated absorbances of the ν^1 bands of the cis-cis HOONO and HONO_2 products were measured as a function of temperature and pressure. These were converted to product branching ratios by scaling the experimentally observed absorbances with ab initio integrated cross sections for HOONO and HONO_2 computed at the CCSD(T)/cc-pVTZ level. The product branching ratio for cis-cis HOONO to HONO_2 was 0.075 ± 0.020(2σ) at room temperature in a 20 Torr mixture of He/Ar/N_2 buffer gas. The largest contribution to the uncertainty is from the ab initio ratio of the absorption cross sections, computed in the double harmonic approximation, which is estimated to be accurate to within 20%. The branching ratio decreased slightly with temperature over the range 270 to 360 K at 20 Torr. Although trans-perp HOONO was not observed, its energy was computed at the CCSD(T)/cc-pVTZ level to be E_0 = +3.4 kcal/mol relative to the cis-cis isomer. Statistical rate calculations showed that the conformers of HOONO should reach equilibrium on the time scale of this experiment. These results suggested that essentially all isomers had converted to cis-cis HOONO; thus, the reported branching ratio is a lower bound for and may represent the entire HOONO yield.

Item Type:Article
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Okumura, Mitchio0000-0001-6874-1137
Sander, Stanley P.0000-0003-1424-3620
Additional Information:© 2003 American Chemical Society. Received 17 February 2003. Published online 19 August 2003. Published in print 1 September 2003. This work was supported by NASA Grants NAG5-11657 and NAGW-3911 and the Upper Atmospheric Research and Tropospheric Chemistry Programs. A.K.M. acknowledges support of an NSF Graduate Research Fellowship, G.N. support by a Caltech SURF Fellowship, and G.N. and S.A.N. by the Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry. Calculations were supported by the NASA JPL Supercomputing Project. We thank D. M. Golden and J. R. Barker for sharing their results prior to publication and A. Goldman for providing spectral data.
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Camille and Henry Dreyfus FoundationUNSPECIFIED
Issue or Number:36
Record Number:CaltechAUTHORS:20170524-071408780
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Official Citation:Cavity Ringdown Spectroscopy of cis-cis HOONO and the HOONO/HONO2 Branching Ratio in the Reaction OH + NO2 + M Brian D. Bean, Andrew K. Mollner, Sergey A. Nizkorodov, Gautham Nair, Mitchio Okumura, Stanley P. Sander, Kirk A. Peterson, and Joseph S. Francisco The Journal of Physical Chemistry A 2003 107 (36), 6974-6985 DOI: 10.1021/jp034407c
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77686
Deposited By: Ruth Sustaita
Deposited On:24 May 2017 17:04
Last Modified:15 Nov 2021 17:33

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