Sub-Doppler excitation spectra of SO2 molecule of the two bands
30548.0 cm−1 and 31770.0 cm−1 have been measured with the help of the
Auto-Scan ring dye laser system, the spectral linewidth was 1.8 GHz when the
band 30548.0 cm−1 was measured without skimmer, while the linewidth was
0.15 GHz with the collimating skimmer. The Doppler linewidth was decreased
to about 0.2 GHz i.e., six times narower than before, by the collimation for the
31770.0 cm−1 band. The molecular rotational constants, the centrifugal
distortion constants and the moment of inertia of the excited state were
calculated. The inertial defects and the valence angle of SO2 molecule of these
bands are tabulated and compared at different conditions.