The spectroscopic and photophysical effects of the position of methyl substitution. II. 2-methylpyrimidine

Article abstract of DOI:10.1063/1.462121

Laser-induced fluorescence excitation and dispersed fluorescence spectra of the first n-?^* transition of jet-cooled 2-methylpyrimidine have been recorded and analyzed.This work extends our earlier study of the spectroscopic and photophysical effects of methyl substitution in 4- and 5-methylpyrimidine.An unusual Fermi resonance invovlving the 6a₀ⁿ progression forms the focus of the present study.The 6a₀¹ vibronic transition is observed to be split into a triad of transitions.Dispersed fluorescence spectra are used to identify the dark background state responsible for the Fermi resonance coupling as the 16b¹(3a''₂) vibration/internal rotation combination level.This level is selectively coupled by symmetry constraints to 6a¹(0a'₁), leaving the 6a¹(1e'') level unperturbed.The positions and intensities of the triad of peaks in the excitation spectrum allow a quantitative determination of the 6a¹(0a'₁) <-> 16b¹(3a''₂) coupling matrix element of V = 4.1 cm^-1.This vibration/internal rotation Fermi resonance is thus typical of the new types of routes to vibrational state mixing which are opened by methyl substitution.Higher members of the 6a₀ⁿ progression are also involved in Fermi resonance mixing.However, in addition, these levels experience weaker, less state-specific coupling to a bath of same-symmetry states at that energy.The excitation spectrum provides an estimate of the average coupling matrix element of this second tier coupling of ca. 1 cm^-1.

Full text of DOI:10.1063/1.462121

The spectroscopic and photophysical effects of the position of methyl
substitution. II. 2methylpyrimidine
Ralph E. Bandy, Aaron W. Garrett, H. D. Lee, and Timothy S. Zwier
Citation: The Journal of Chemical Physics 96, 1667 (1992); doi: 10.1063/1.462121
View online: http://dx.doi.org/10.1063/1.462121
View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/96/3?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:
28.123.44.23 On: Sun, 21 Dec 2014 07:57:41
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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:
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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:
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