THE ELECTRONIC ABSORPTION SPECTRUM OF THE 0-0 BAND OF THIONAPHTHENE.
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Date
1969
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Ohio State University
Abstract
The 0-0 band of the $\pi^{\ast} \leftarrow \pi$ transition of thionaphthene at $2936\AA$ was recorded using an 8-meter Czerny mount spectrometer with a resolving power of approximately 500,000 and a linear dispersion on the order of $1 cm/{\AA}$. The main features of the spectrum include Q and P sub-bands and two intense maxima. Using computer simulation techniques it has been possible to determine the excited state rotational constants to a high degree of accuracy and to demonstrate conclusively the hybrid character of the band. The latter yields the direction of the transition moment. Using ground state rotational constants of $A"" = 0.104335 cm^{-1}, B"" = 0.042772 cm^{-1}$ and $C"" = 0.030336 cm^{-1}$ as determined from assumed bond angles and lengths, the excited state values obtained from the best fit of computed with experimental contour are $A^{\prime} = 0.100182 cm^{-1}, B^{\prime} = 0.042157 cm^{-1}$ and $C^{\prime} = 0.029671 cm^{-1}$. The prominent peak approximately $3 cm^{-1}$ to the blue of the main peak cannot be fit by pure A-type computation and is found to result from a B-type contribution, while most of the rotational fine structure is due to an A-type band. Mixing of various amounts of A-type and B-type character yields the direction of the transition moment.
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Author Institution: The William Albert Noyes Laboratory Department of Chemistry, University of Illinois