Ultrafast dynamics of the SO2(H2O)n cluster system.

An investigation of the excited-state dynamics of SO2(H2O)n (n = 1−5) clusters following excitation by ultrafast laser pulses to 4.7 eV (coupled 1A2 and 1B1 states) and 9.3 eV (F band) is presented. The findings for the coupled 1A2 and 1B1 states are in good agreement with published computational work7 and indicate the division of the initial excited-state population into the double well produced by the coupled states. A photoinduced ion-pair formation process is proposed as a likely source of the observed dynamic behavior following the 9.3 eV excitation. Energetics calculations are also presented that support the ion-pair mechanism. A lack of cluster size dependence in the measured time constants indicate surface solvation of SO2 rather than a cluster structure with the SO2 molecule fully encompassed by water molecules.