Rotation-dependent intramolecular processes of SO2(Ã1A2) in a supersonic jet

Abstract

Rotationally cooled SO₂ is prepared through supersonic expansion of its seeded mixture in Ar and is excited to the first electronically allowed state by a frequency-doubled dye laser pulse in the wavelength range of 300–320 nm, in particular, in “E” and “G” bands region, using Clements' notation. In the time-resolved fluorescence measurements with a 0.02 cm^–1 excitation bandwidth, all of the rovibronic levels examined exhibit apparent biexponential decay having a short lifetime of 3–5 µs and a long one of 15–30 µs. With application of a weak magnetic field (<50 G) some rovibronic lines show a beating fluorescence decay dependent on the field strength. The beating phenomenon has been analysed based on the classical theory of Zeeman quantum beats. The derived g-values distribute rather irregularly over a wide range, which indicates a complicated coupling among the relevant electronic states. At present the coupling mechanism which causes a sizeable magnetic moment seems to be quite independent of the coupling mechanism which results in the observed apparent biexponential decay.