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Title: Tunneling effects in the unimolecular decay of (CH 3) 2COO Criegee intermediates to OH radical products

Unimolecular decay of the dimethyl substituted Criegee intermediate (CH 3) 2COO is observed at energies significantly below the transition state barrier associated with hydrogen atom transfer with time-resolved detection of the resultant OH radical products. (CH 3) 2COO is prepared at specific energies in the 3900-4600 cm -1 region through IR excitation of combination bands involving CH stretch and another lower frequency mode, and the OH products are detected by UV laser-induced fluorescence. OH appearance times on the order of microseconds are observed in this deep tunneling regime, which are about 100 times slower than that in the vicinity of the barrier. The experimental rates are in good accord with Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of the microcanonical dissociation rates for (CH 3) 2COO that include tunneling. Master equation modeling based on these microcanonical rates is used to predict the thermal decay rate of (CH 3) 2COO to OH products under atmospheric conditions of 276 s -1 at 298 K (high pressure limit). Furthermore, thermal unimolecular decay of (CH 3) 2COO to OH products is shown to have significant contributions from tunneling at energies much below the barrier to H-atom transfer.
Authors:
ORCiD logo [1] ;  [1] ; ORCiD logo [2] ; ORCiD logo [3] ; ORCiD logo [1]
  1. Univ. of Pennsylvania, Philadelphia, PA (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Univ. of Washington, Seattle, WA (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 146; Journal Issue: 13; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22), Chemical Sciences, Geosciences, and Biosciences Division; USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1371548
Alternate Identifier(s):
OSTI ID: 1361798

Fang, Yi, Barber, Victoria P., Klippenstein, Stephen J., McCoy, Anne B., and Lester, Marsha I.. Tunneling effects in the unimolecular decay of (CH3)2COO Criegee intermediates to OH radical products. United States: N. p., Web. doi:10.1063/1.4979297.
Fang, Yi, Barber, Victoria P., Klippenstein, Stephen J., McCoy, Anne B., & Lester, Marsha I.. Tunneling effects in the unimolecular decay of (CH3)2COO Criegee intermediates to OH radical products. United States. doi:10.1063/1.4979297.
Fang, Yi, Barber, Victoria P., Klippenstein, Stephen J., McCoy, Anne B., and Lester, Marsha I.. 2017. "Tunneling effects in the unimolecular decay of (CH3)2COO Criegee intermediates to OH radical products". United States. doi:10.1063/1.4979297. https://www.osti.gov/servlets/purl/1371548.
@article{osti_1371548,
title = {Tunneling effects in the unimolecular decay of (CH3)2COO Criegee intermediates to OH radical products},
author = {Fang, Yi and Barber, Victoria P. and Klippenstein, Stephen J. and McCoy, Anne B. and Lester, Marsha I.},
abstractNote = {Unimolecular decay of the dimethyl substituted Criegee intermediate (CH3)2COO is observed at energies significantly below the transition state barrier associated with hydrogen atom transfer with time-resolved detection of the resultant OH radical products. (CH3)2COO is prepared at specific energies in the 3900-4600 cm-1 region through IR excitation of combination bands involving CH stretch and another lower frequency mode, and the OH products are detected by UV laser-induced fluorescence. OH appearance times on the order of microseconds are observed in this deep tunneling regime, which are about 100 times slower than that in the vicinity of the barrier. The experimental rates are in good accord with Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of the microcanonical dissociation rates for (CH3)2COO that include tunneling. Master equation modeling based on these microcanonical rates is used to predict the thermal decay rate of (CH3)2COO to OH products under atmospheric conditions of 276 s-1 at 298 K (high pressure limit). Furthermore, thermal unimolecular decay of (CH3)2COO to OH products is shown to have significant contributions from tunneling at energies much below the barrier to H-atom transfer.},
doi = {10.1063/1.4979297},
journal = {Journal of Chemical Physics},
number = 13,
volume = 146,
place = {United States},
year = {2017},
month = {4}
}