New dispersed fluorescence spectra of HCBr and DCBr

Dispersed fluorescence spectra following the excitation of several HCBr and DCBr A ˜ – X ˜ vibronic bands were successfully obtained in a supersonic free jet expansion with an intensified charge-coupled device (ICCD) detector. These dispersed fluorescence spectra show signal-to-noise ratios of up to 100 and reveal the complete and detailed vibrational structure of the ground singlet state including the previously unreported C–H/D stretch vibrational mode. The emission bands to the background triplet state levels in DCBr were also observed for the first time and this confirms the singlet–triplet energy gap to be 2061 cm−1 (5.89 kcal/mol) in DCBr.