Laser excitation and dispersed fluorescence spectra of the HCBr ÖX̃ vibronic transition

Abstract

We recorded the laser-induced fluorescence (LIF) excitation spectra of several HCBr ÖX̃ vibronic transitions between 580 nm and 630 nm in a direct current (DC) discharge supersonic free jet expansion. Dispersed fluorescence spectra, following excitation of these HCBr ÖX̃ vibronic transitions were successfully obtained for the first time. The analysis of the dispersed fluorescence spectra reveals the details of the vibrational structure of the X̃ 1A′ state as well as that of the ã 3A″ state. The vibrational frequencies were determined as 1119 cm−1 (bend), 676 cm−1 (C–Br stretch) for the X̃ 1A′ state and 994 cm−1 (bend), 733 cm−1 (C–Br stretch) for the ã 3A″ state. In addition, based upon the observation of the triplet state levels, the value of the triplet–singlet energy gap (the zero-point level energy gap) could be extracted from the dispersed fluorescence spectra and is to be approximately 2006±8 cm−1 (5.73±0.02 kcal/mol).