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 τ_o of resolved ro-vibrational states of IBr (B) with ν′= 2, 3 and 34 ≥J′≥ 0 were determined. Values for τ_o decreased as a function of increasing J′ and were lower in the ν′= 3 state than in the ν′= 2 state. All values of τ_o 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.