Probing the NO2 -> NO + O transition state via time resolved unimolecular decomposition

Article abstract of DOI:10.1063/1.465152

Time resolved, subpicosecond resolution measurements of photoinitiated NO2 unimolecular decomposition rates are reported for expansion cooled and room temperature samples.The molecules are excited by 375-402 nm tunable subpicosecond pulses having bandwidths <*> 20 cm^-1 to levels which are known to be thorough admixtures of the ²B₂ electronically excited state and the ²A₁ ground electronic state.Subsequent decomposition if probed by a 226 nm subpicosecond pulse that excites laser-induced fluorescence (LIF) in the NO product.When increasing the amount of excitation over the dissociation threshold, an uneven, step-like increase of the decomposition rate vs energy is observed for expansion cooled samples.The steps are spaced by ca. 100 cm^-1 and can be assigned ad hoc to bending at the transition state.Relying on experimental estimates for the near threshold density of states, we point out that simple transition state theory predictions give rates that are consistent with these measured values.The rates are sufficiently rapid to question the assumption of rapid intramolecular vibrational redistribution, which is implicit in transition state theories.In contrast to expansion cooled samples, room temperature samples exhibit a smooth variation of the reaction rate vs photon energy.By comparing rates for rotationally cold and room temperature NO2, the ON-O bond is estimated to be ca. 40percent longer in the transition state than in the parent molecule.

Full text of DOI:10.1063/1.465152

Probing the NO2→NO+O transition state via time resolved unimolecular
decomposition
S. I. Ionov, G. A. Brucker, C. Jaques, Y. Chen, and C. Wittig
Citation: The Journal of Chemical Physics 99, 3420 (1993); doi: 10.1063/1.465152
View online: http://dx.doi.org/10.1063/1.465152
View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/99/5?ver=pdfcov
Published by the AIP Publishing
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This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
129.105.215.146 On: Sat, 20 Dec 2014 00:19:37