Laser-induced fluorescence studies: the B–X transition of Cl2. Part 1.—Rotationally-resolved excitation spectra and predissociation in the excited B3Π(0 +u) state

Abstract

Excitation of resolved ro-vibrational states of Cl₂B³Π(0⁺_u) has been carried out using a pulsed dye laser, with pressures of Cl₂ between 0.1 and 30 mTorr. Laser-induced fluorescence was observed with unit quantum yield at low pressures, following excitation of levels v′⩽ 12 at wavelengths 501.4 nm.

No fluorescence was seen after excitation of higher levels v′ 13 using wavelengths 478 ⩽λ⩽ 501.4 nm. These higher levels, v′ 13 of B³Π(0⁺_u), are thus strongly predissociated. The very weak fluorescence from these states, which was observed previously using high pressures of Cl₂ with continuous wave excitation, is estimated to have a quantum yield of ≈ 3 × 10^–5.