Mechanism and deactivation kinetics of S2-xanthione in acetonitrile, a quenching solvent, and of S2-exciplex measured by pico- and femtosecond laser spectroscopy (original) (raw)

The Letter discusses the mechanism and dynamics of intra-and intermolecular electronic relaxation of the S 2 state of a xanthione molecule in acetonitrile, a quenching solvent, as well as the most important properties of the S 2 -exciplex formed upon the quenching process. Despite very ecient quenching of S 2 -XT and other thiones it has not been possible so far to observe the S 2 -exciplex. Therefore transient absorption system with 120 fs resolution was successfully applied for this purpose: the S 2 -exciplex was identi®ed for the ®rst time, its lifetime ($30 ps) and transient absorption spectrum were determined as well as the mechanism of its formation and decay. Moreover, the authors observed the presence of a very fast intramolecular electronic relaxation process S v>0 2 3 S 0 during S 2 -state deactivation which competes with intramolecular vibrational redistribution in the S 2 -state. Ó