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Femtosecond Dynamics of Pyridine in the Condensed Phase: Valence Isomerization by Conical Intersections

Chachisvilis, Mirianas and Zewail, Ahmed H. (1999) Femtosecond Dynamics of Pyridine in the Condensed Phase: Valence Isomerization by Conical Intersections. Journal of Physical Chemistry A, 103 (37). pp. 7408-7418. ISSN 1089-5639. doi:10.1021/jp991821x.

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In this work, we combined femtosecond transient absorption (population and anisotropy) spectroscopy with ab initio electronic structure methods to study excited-state deactivation pathways of the pyridine molecule in liquid solutions. Studies of the effects of excitation energy, deuteration and substitution, solvent polarity and viscosity, and protonation of pyridine were performed. The experiments reveal the dynamics of S_1(nπ^*) and S_2(ππ^*) excited states of pyridine. The photoexcitation of the S_2(ππ^*) state leads to formation of the prefulvenic form of pyridine, a valence isomer, in ∼2.2 ps, while nonradiative deactivation of the S_1(nπ^*) state occurs in 9−23 ps and is to a large extent due to intersystem crossing. Using ab initio methods at the CASSCF and time-dependent DFT levels, we calculated the potential energy surfaces of the ground and S_2(ππ^*) states. A conical intersection was found responsible for the ultrafast deactivation of the pyridine molecule.

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Additional Information:© 1999 American Chemical Society. Received: June 3, 1999. Publication Date (Web): August 31, 1999. This work was supported by the National Science Foundation. M.C. is grateful to Swedish Foundation for Research and higher Education (STINT) for financial support. The authors also thank Dr. E. W.-G. Diau for helpful discussions about ab initio methods.
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Swedish Foundation for Research and Higher EducationUNSPECIFIED
Issue or Number:37
Record Number:CaltechAUTHORS:20160823-093536570
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Official Citation:Femtosecond Dynamics of Pyridine in the Condensed Phase:  Valence Isomerization by Conical Intersections Mirianas Chachisvilis and Ahmed H. Zewail The Journal of Physical Chemistry A 1999 103 (37), 7408-7418 DOI: 10.1021/jp991821x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69843
Deposited By: Ruth Sustaita
Deposited On:23 Aug 2016 18:59
Last Modified:11 Nov 2021 04:20

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