Visible Wavelength Electronic Spectroscopy of the DCBr ÖX̃ Vibronic Transition

Abstract

The laser excitation and dispersed fluorescence spectra of the DCBr ÖX̃ vibronic bands between 570 and 600 nm were successfully obtained in a direct current (DC) discharge supersonic free jet expansion. The analysis of the dispersed fluorescence spectra results in information on the vibrational structure of the DCBr X̃1A′ state for the first time. Perturbations due to the background levels of the ã3A″ state can be recognized. The data are consistent with the previously reported triplet-singlet energy gap (the zero-point level energy gap) of 5.73±0.02 kcal/mol for HCBr. We have determined the vibrational frequencies to be 832 cm−1 (bend) and 663 cm−1 (C–Br stretch) for the X̃1A′ state. In addition to the X̃ state vibrational structure, the Ã(0,6,2) and Ã(0,5,0) levels were also observed for the first time.