Ultrafast Spectroscopy

The processes of interest occur very fast (10-15-10-10sec). These events are triggered by the absorption of energy from a laser pulse. After excitation, the systems can undergo several changes, involving redistribution of the energy, lose of coherence, formation of intermediates, etc. The evolution of those changes provides useful information to understand the light-matter interactions. Since the temporal evolutions are extremely fast, it is necessary to probe the system in time-scales faster that the times it takes them to evolve. In general, ultrafast spectroscopy techniques involve an initial step (excitation by a short laser pulse) followed by the probing of the evolution of an optical transition (through absorption, scattering or photoluminescence) . To probe the evolution of a fast process we utilize techniques equivalent to the stroboscopic method develop by Harold “Doc” Edgerton. In our experiments, as the system is evolving in time we collect snapshots of a chosen property, modulated by the initial absorption of energy. For example, at t=0, a conjugated polymer is excited with visible or UV light, After that triggering event, the energy is transferred to low lying energy levels of the polymer or to a quencher/acceptor. By monitoring the time evolution of the polymer fluorescence together with the time-evolution of the acceptor’s fluorescence, we can build a set of snapshot describing the energy transfer process. Reseearch These programs are inherently interdisciplinary with involvement from physical chemists, materials scientists, and synthetic chemists. If you are interested on learning more about our work, please contact me directly at kleiman@chem.ufl.edu.