Collision-induced intersystem crossing rate constants from the (0,4,1) and (1,2,1) levels of the (A) over tilde(1)A(2) to (a) over tilde(3)B(1) State and rovibronic relaxation rate constants in the (A) over tilde(1)A(2) state of SO2 have been studied. The laser wavelength was set at 335.86 and 334.09 nm:for the (0,4,1) and (1,2,1) excitation, respectively. When a few rotational levels belonging to the (0,4,1) and (1,2,1) vibrational levels were populated by a narrow bandwidth laser, both the fluorescence from the (A) over tilde(1)A(2) State and the phosphorescence from the (a) over tilde(3)B(1) State were observed from the time resolved emission spectra. The decay behavior of the fluorescence signal showed fast and slow components. The radiative lifetimes and apparent quenching rate constants obtained from the fast component analysis are 38+/-5 and (9.8 +/- 0.2) X 10(-10) for (0,4,1) excitation and 33+/-5 mu s and (1.0 +/- 0. 1) X 10(-9) cm(3) mol(-1) s(-1) for (1,2,1) excitation, respectively. The effective lifetimes and quenching rate constants for the slow component are 280+/-100 and(1.5+/-0.1) X 10(-10) for (0,4,1) excitation and they are 220+/-100 mu s and (1.6+/-0.1) X 10(-10) cm(3) mol(-1) s(-1) for (1,2,1) excitation. Based on the measured rate constants, kinetic simulations of the emission profiles were done to obtain the magnitudes of intersystem crossing and rovibronic relaxation rate constants. The magnitudes of the rovibronic relaxation and the intersystem crossing rate constants are found to be in the range of 8.5-10.0 X 10(-10) and 1.3-1.5 X 10(-10) cm(3) mol(-1) s(-1), respectively.