SPECTROSCOPY OF JET-COOLED BENZIMIDAZOLE AND BENZOTRIAZOLE

Laser-induced fluorescence excitation and dispersed fluorescence spectra of jet-cooled benzimidazole and benzotriazole molecules are reported. The first excited singlet state is assigned to 1L(b) for benzimidazole (origin at 36032 cm-1) and to 1L(a) for benzotriazole (origin at 34927 cm-1). A rapid nonradiative decay is found to occur for benzotriazole above 1200 cm-1 from S1 origin. The spectra of benzimidazole show a good Franck-Condon overlap between S0 and S1 (1L(b)) states. For benzotriazole progressions of several in-plane modes (540, 1153, 1242, 1405 and 1447 cm-1) cover about 8000 cm-1 of the dispersed fluorescence spectrum following excitation into the origin of the Si(1L(a)) state.