The study of laser induced dispersive fluorescence spectra of SO2 by time tomographic scanning

The paper presented one study on the complicated de-excitation process of the first-excited band of SO2 molecule, including fluorescence radiation and collision relaxation, using gated enhanced optical multi-channel spectrum analyzer (OMA)and the quadruple harmonic output (266 nm) of a nanosecond pulsed Nd: YAG laser as excitation source. The time tomographic scanning results showed that the fluorescence spectrum envelopes centered in 305.6 nm and 337.2 nm and the regular fluorescence lines centered in 424.7 nm in the laser induced dispersive fluorescence spectra (LIDFS) were attributed to transitions to the different vibrational levels of ground electronic state X1A1 from low vibrational levels of B1A1, A1A2 and the ground vibrational level a3B1 respectively. The sensitive detection wavelength (425 nm) of SO2 gas was confirmed by the experiment. The harmonic frequencies of the symmetry stretch vibration (ω1 = 1151.8 cm-1 ± 0.6 cm-1) and the bend vibration (ω2 = 517.8 cm-1 ± 0.6 cm-1) of X1A1 state were also calculated from the experimental data. The anharmonic constants of stretch vibration mode and the bend vibration mode are χ11 = 8 ± 0.6 cm-1 and χ22 = 9.2 ± 0.6 cm-1 respectively. (authors)