Communication: Real time observation of unimolecular decay of Criegee intermediates to OH radical products
- Univ. of Pennsylvania, Philadelphia, PA (United States)
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Univ. of Washington, Seattle, WA (United States). Dept. of Chemistry
In the atmosphere, a dominant loss process for carbonyl oxide intermediates produced from alkene ozonolysis is also an important source of hydroxyl radicals. In this work, the rate of appearance of OH radicals is revealed through direct time-domain measurements following vibrational activation of prototypical methyl-substituted Criegee intermediates under collision-free conditions. Complementary theoretical calculations predict the unimolecular decay rate for the Criegee intermediates in the vicinity of the barrier for 1,4 hydrogen transfer that leads to OH products. Both experiment and theory yield unimolecular decay rates of ca. 108 and 107 s–1 for syn-CH3CHOO and (CH3)2COO, respectively, at energies near the barrier. Tunneling through the barrier, computed from high level electronic structure theory and experimentally validated, makes a significant contribution to the decay rate. Extension to thermally averaged unimolecular decay of stabilized Criegee intermediates under atmospheric conditions yields rates that are six orders of magnitude slower than those evaluated directly in the barrier region.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division
- Grant/Contract Number:
- AC02-06CH11357; CHE-1362835; CHE-1465001; CHE-1213347
- OSTI ID:
- 1350086
- Alternate ID(s):
- OSTI ID: 1237774
- Journal Information:
- Journal of Chemical Physics, Vol. 144, Issue 6; ISSN 0021-9606
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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