Femtosecond Resolving Photodissociation Dynamics of SO2 Molecule.

We experimentally investigate the ultrafast photodissociation dynamics of SO2 molecules induced by intense ultrashort laser pulses in a pump-probe scheme. Different three-body fragmentation pathways are discriminated using the time-dependent kinetic energy release spectrum with femtosecond time resolution. A nontrivial three-body fragmentation pathway, denoted as the bonding pathway, is unraveled, in which an intermediate fast rotating O2 molecule is formed before complete fragmentation. The ultrafast chemical bond rearrangement after electron releasing are tracked at real time. The bonding pathway generally exists in the three-body fragmentation processes induced by strong laser fields of different wavelengths, which is observed in infrared, ultraviolet and mixed two-color cases. Our findings are significant for understanding the photon-induced ultrafast processes of SO2 molecules in atmospheric chemistry.