Laser-induced fluorescence studies: the B–X transition of Cl2. Part 4.—Predissociation in the B state
Abstract
Laser-induced fluorescence has been used to determine the lifetimes of resolved ro-vibrational levels (v′, J′) in the predissociated parts of the excited B3Π(0+u) manifold of 35Cl35Cl. Determinations were made over the ranges 13 ⩽v′⩽ 25 (except v′= 17, 20), and 0 ⩽J′⩽ 10.
The lifetimes (τ0) showed strong variations with both rotational and vibrational quantum numbers, according to expression (II), 1/τ0= 1/τ00+kv′J′(J′+ 1). (II) The mean value for the rotation-free lifetime τ00 showed no significant dependence upon v′ in the range 13 ⩽v′⩽ 25.
The rotationally-dependent part of the predissociation in Cl2(B) is assigned to a strong heterogeneous interaction (ΔΩ= 1) of the bound B3Π(0+u) state and the unbound 1Π(1u) state. Values for kv′(s–1) varied from 7.1 × 105 for v′= 13, down to 1.2 × 105 for v′= 25. These values are much greater than those of kv′ found previously for the similar heterogeneous predissociations in Br2 and I2, indicating a much stronger B3Π(0+u)–1Π(1u) interaction in Cl2.
The significance of these results in the spectroscopy and photochemistry of Cl2 is discussed.