S1 ← S0 hole-burning spectroscopy of jet-cooled dithienylethylene and dithienylbutadiene vapors

S1 ← S0 hole-burning spectra have been measured for jet-cooled α, ω-dithienylethylene (DTE) and α, ω-dithienylbutadiene (DTB) vapors, along with the excitation and fluorescence spectra. The S1 origins of the two conformers of DTE vapor were observed at 28 648 and 28 966 cm−1, which are assigned to those of the anti–syn and anti–anti forms, respectively. With DTB vapor, the apparent S1 origin of the main conformer (anti–anti) was observed at 25 471 cm−1 and the S1 origin of the minor conformer was observed at 25 678 cm−1. The minor conformer can be assigned to the anti–syn conformer. These results are in agreement with those obtained recently [T. Itoh, Y. Numata, J. Phys. Chem. A 113 (2009) 10160].