15min:

MASAAKI BABA, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan; ATSUSHI DOI, YOSHIO TATAMITANI, MICHIRU YAMAWAKI, SHUNJI KASAHARA AND HAJIME KATÔ, Molecular Photoscience Research Center, Kobe University, Kobe 657-8501, Japan.

Dibenzofuran (DF) is one of the prototypical molecules of toxic dioxins as well as dibenzo-p-dioxin.\footnoteM. Baba, A. Doi, Y. Tatamitani, S. Kasahara, and H. Katô, J. Phys. Chem. A , 108, 1388 (2004) Sub-Doppler high-resolution fluorescence excitation spectra of the S₁ S₀ transition of DF have been observed in a collimated molecular beam. Each rotational line was fully resolved and the rotational constants in both the S₀ and S₁ states were determined by the rotational analysis of the 0-0 band (33773.478 cm^-1). The DF molecule has shown to be planar both in the S₀ and S₁ states. All of the observed lines were the K = \pm 1 transition (B type). Therefore, the S₁ state is assigned to be the ¹A₁ state in C_2v symmetry.