Emission spectrum and relaxation kinetics of SO2 induced by 266Â nm laser

Laser induced fluorescence (LIF) emission spectrum of SO2 in the range of 270.0-470.0 nm has been obtained with the quadruple harmonic output (266 nm) of a pulsed Nd:YAG laser as excitation source. The spectrum is composed of a continuous envelope in the short wavelength side, while it shows the character of banded structure superimposed on a continuous one in the long wavelength region. Fluorescence emission from the hybrid states of A1A2 + B1B1 and X1A1 + B1B1 forms the continuous envelope and phosphorescence emission from the triplet state a3B1 forms the banded progression. It is also found that direct emission from laser excited states is very weak. The primary portion of the emission is from the energy levels populated by collision relaxation or collision induced intersystem crossing process. The harmonic frequencies and inharmonic coefficients of the symmetric stretching vibration and the bending vibration of X1A1 state are derived from the ascription of the phosphorescence progression.