Laser-induced fluorescence studies: the B–X transition of Cl2. Part 5.—Radiative lifetime of the B state

Abstract
A redetermination of the radiative lifetime of the long-lived B3Π(Ou +)state of 35Cl35Cl is described. Pulses of narrow-band radiation from a scanning dye laser (> 1 mJ pulse–1) were used to excite the v′= 5, J′= 16 state of Cl2(B). Decay of fluorescence in real time was used to determine τR for the v′= 5 state: τR=(305 ± 15)µs (1σ). Reasons for error in previous work are discussed. The long radiative lifetime of Cl2(B) is consistent with estimates based on absorption coefficient measurements in the ultraviolet continuum of Cl2. The low efficiency at 298 K of electronic self-quenching of Cl2(B) is confirmed, with k Q,Cl2 =(6.4 ± 0.6)× 10–12 cm3 molecule–1 s–1. Quenching by Ar, N2 and O2 also is inefficient, with kQ,Ar⩽ 4.9 × 10–12, k Q,N2 ⩽ 1 × 10–11 and k Q,O2 ⩽ 1 × 10–11 cm3 molecule–1 s–1.

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