MASAKAZU NAKAJIMA, HITOMI TOYOSHIMA, YU YONEDA, YOSHIHIRO SUMIYOSHI AND YASUKI ENDO, Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan .
New vibronic band system has been observed in the 21800-23000 cm-1 region by laser-induced fluorescence spectroscopy in a discharged supersonic jet of the C2H2 and CS2 mixture gas. Several chemical tests indicate that the spectral carrier contains H, C and S atom(s). High-resolution spectra of these vibronic bands show - type rotational structures. The origin band position and the effective rotational constants of the upper and lower levels have been determined to be T 0=21877.7706(7), B '_ eff =0.04932(1) and B ''_ eff =0.05013(2)cm-1, respectively. Based on the results of ab initio calculations, it is considered that bent HSCCS is the most probable candidate for the spectral carrier.