Kinetics of excited states of Br2using laser excitation. Part 1 .—System description and rotationally-dependent lifetimes in Br2(B)

Abstract
A pressure-tuned narrow-band day laser is described. This instrument was used to provide linear scans, free of mode hops, of selected parts of the Br2(B–X) band spectrum in laser-induced fluorescence. Resolution was Doppler limited. Measurements of collision-free lifetimes τ0 of Br2(B) excited molecules were made over a range of rotational states J′, for several vibrational states 23 v′ 11. A strong dependence of Γ0= 1/τ0 upon J′, was found, which was attributed to a heterogeneous predissociation of the emitting B3Π(0+ u) state. The results gave a good fit to the relationship, Γ0=ΓR+kv′J′(J′+ 1). The mean value of the radiative, rotation-free lifetime (τR= 1/ΓR) was 8.1 µs for 24 v′ 11. The results show that virtually all band absorption of Br2 between 540 and 590 nm leads to formation of 2P+2P bromine atoms via predissociation.

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