Laser-induced fluorescence studies: B–X transition of Cl2. Part 2.—Transition from bound to unbound excited states

Abstract

Laser-induced fluorescence has been used to determine the collision-free lifetimes of resolved ro-vibrational levels (v′, J′) of the excited B³Π(0⁺_u) states of ³⁵Cl³⁵Cl and ³⁵Cl³⁷Cl. Predissociation affects all vibrational states above v′= 12, giving undetectably weak fluorescence and lifetimes estimated to be 3 ns.

Lifetimes of selected rotational levels of the stable (v′, J′) states were determined for 12 v′ 7. The mean collision-free lifetime for these states was τ₀=(83 ± 5)µs.

Observations on the highest-energy (12, J′) states before predissociation have provided close upper limits for the dissociation energy D⁰₀(³⁵Cl³⁵Cl) and D⁰₀(³⁵Cl³⁷Cl). There is a negligible energy barrier to predissociation of B-states. Predissociation of the B-state of Cl₂ occurs by crossing with the ¹Π(1_u) repulsive state at a relatively short internuclear distance.