COLOR-CENTER LASER SPECTRUM OF THIOPHENE OBSERVED WITH THE PULSED SUPERSONIC JET EXPANSION TECHNIQUE

$^{a}$ T.D. Klots, R.D. Chirico, and W.B. Steele, Spectrochim. Acta. 50A, 765 (1994) $^{b}$ A.A. El-Azhary, and R.H. Hilal, Spectrochim. Acta, 53A, 1365 (1997) $^{c}$ B. Pankoke, K.M.T. Yamada, and G. Winnewisser, Z. Naturforsch. 49a, 1193 (1994)Author Institution: Department of Chemistry, Faculty of ScienceThe high resolution infrared spectrum of thiophene in the CH-stretch region $(3070-3140 cm^{-1})$ has been observed with a color-center laser spectrometer combined with a pulsed supersonic jet expandion technique. Of 4 fundamental bands $(a_{1}; \nu_{1}, \nu_{2}, b_{1}; \nu_{12}, \nu_{13})$ expected in this region, the $\nu_{2}$ band was analyzed to the confirmation of previous vibrational $assignment.^{a b}$ The rotational constants and band origin were derived from the observed spectra while the ground state constants were fixed at the microwave $values.^{c}$ The $\nu_{2}$ band was found to be overlapped by an $a_{1}$ vibrational band, which is denoted as $\nu_{x}$. The $\nu_{x}$ band presumably borrows the intensity from the $\nu_{2}$ band by Fermi resonance. The vibrational assignment of $\nu_{x}$ is not get clear, but the magnitude of the interaction between the $\nu_{2}$ and $\nu_{x}$ states is calculated to be $0.8 cm^{-1}$ from the analysis of the intensity ratio of these bands