Visible wavelength electronic spectroscopy of the DCBr (A)over-tilde-(X)over-tilde vibronic transition

The laser excitation and dispersed fluorescence spectra of the DCBr (A) ove r tilde-(X) over tilde vibronic bands between 570 and 600 nm were successfu lly obtained in a direct current (DC) discharge supersonic free jet expansi on. The analysis of the dispersed fluorescence spectra results in informati on on the vibrational structure of the DCBr (X) over tilde (1)A' state for the first time. Perturbations due to the background levels of the (a) over tilde (3) A" state can be recognized. The data are consistent with the prev iously 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 fr equencies to be 832 cm(-1) (bend) and 663 cm(-1) (C-Br stretch) for the (X) over tilde (1)A' state. In addition to the (X) over tilde state vibrationa l structure, the (A) over tilde (0,6,2) and (A) over tilde (0,5,0) levels w ere also observed for the first time. (C) 2001 Academic Press.