Laser-induced fluorescence of jet-cooled IBr: B³Π₀+ ← X¹Σ⁺ excitation spectra

The laser-induced fluorescence excitation spectrum of the B ← X transition in IBr seeded in a He supersonic free jet expansion has been recorded. The (1,0), (2,0), and (3,0) transitions are observed with sufficient signal-to-noise to extract the relative fluorescence quantum yields for the v′ = 1, 2, and 3 vibrational levels. All three levels are found to undergo predissociation to some degree, in contrast to the case of ICl, in which the v′ = 1 level in the B state appears stable with respect to dissociation. These differences are discussed in light of the available curve-crossing parameters. No evidence is found in the laser-induced fluorescence excitation spectra for transitions associated with the NeIBr van der Waals complex, possibly due to rapid relaxation mechanisms.