TITLE

The singlet–triplet spectroscopy of 1,3-butadiene using cavity ring-down spectroscopy

AUTHOR(S)
Robinson, Allison G.; Winter, Paul R.; Zwier, Timothy S.
PUB. DATE
May 2002
SOURCE
Journal of Chemical Physics;5/8/2002, Vol. 116 Issue 18, p7918
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The T[sub 1] ← S[sub 0] absorption spectrum of gas-phase 1,3-butadiene ([sub C][H[sub 6]) has been investigated over the region from 20 500 to 23 000 cm[sup -1] using cavity ring-down spectroscopy. Resolved vibrational structure and partially resolved rotational structure have been observed for the first time in the gas phase. The T[sub 1] ← S[sub 0] origin transition is located at 20 777 cm[sup -1], with a peak absorption cross section of 2.5 x 10[sup -26] cm[sup 2]/molecule. Vibronic bands appear 249, 491, 1166, and 1617 cm[sup -1] above the origin. This structure is observed on top of a rising background whose absolute magnitude and wavelength dependence is quantitatively accounted for as Rayleigh scattering. Using the recent calculations of Brink et al. [J. Phys. Chem. A 102, 6513 (1998)] as a guide, the bands 491, 1166, and 1617 cm[sup -1] above the origin can be assigned as totally symmetric fundamentals, while the band 249 cm[sup -2] above the origin is the first overtone of the b[sub g] symmetry CH[sub 2] torsion (calculated at 129.6 cm[sup -1]) of a planar T[sub 1] excited state. The rotational band contour of the origin transition shows several sharp band-heads that appear in doublets with a splitting of 2 cm[sup -1]. Only part of this structure can be accounted for as a single vibronic band. The possible explanations for the remaining band heads and the observed Franck-Condon intensities are discussed in terms of the shape of the T[sub 1] potential energy surface.
ACCESSION #
6554345

 

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