Laser-induced fluorescence of IBr: the B3Π(0+) excited state

Abstract
Quantum-resolved fluorescence from excited IBr B3Π(0+)–X1+ has been observed for the first time. A narrow-band pulsed dye laser, pumped by a doubled Nd-YAG laser, was used to excite IBr at wavelengths between 630 and 650 nm. Excited-state vibrational levels with ν′≤ 3 were observed to emit fluorescence; all higher levels evidently were completely predissociated. The lifetimes τo of resolved ro-vibrational states of IBr (B) with ν′= 2, 3 and 34 ≥J′≥ 0 were determined. Values for τo decreased as a function of increasing J′ and were lower in the ν′= 3 state than in the ν′= 2 state. All values of τo were much shorter than the estimated radiative life-time, indicating that predissociation of moderate strength affects the ν′= 2 and ν′= 3 ro-vibrational manifolds. Both rotation-free and rotationally-dependent predissociations were present in IBr (B) and possible mechanisms for the predissociations are discussed.

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