Studies of ultrafast reaction dynamics in the excited states of molecules in solution

In the course of a photochemical reaction, reactants are converted into products with the possibility of various transition states and transient intermediates on the reaction pathway. The properties of these transient intermediate species are central to the reaction and determine its rate and selectivity. Lifetimes of these intermediates vary from a few tens of a femtosecond to a few picoseconds. In condensed phase chemical reactions, the dynamics of solute-solvent interaction also play a significant role in determining the fate of the transients and intermediates, and hence the rates of the chemical reactions undergone by them. Ultrafast transient absorption spectroscopic techniques developed in our laboratory have enabled us to investigate the numerous number of intra- and intermolecular processes undergone by the excited states and the other intermediate species produced following optical excitation of a solute molecule in condensed phase with femto and picosecond time resolution. This presentation discusses briefly the results of our studies on the excited state dynamics and photophysical and photochemical processes in LDS-821 dye and fullerene molecules in solution and also the bond-breaking dynamics of HgI 2 in ethanol solution.