Femtosecond Pump–Probe Spectroscopy of Photoinduced Tautomerism

Photoreactions leading to tautomers can be extremely fast. In this case femtosecond pump-probe spectroscopy is an ideal tool to study such reactions. It provides an ultrahigh time resolution and allows following the associated processes in real time. Thereby an improved notion of the reaction path and the mechanism is obtained. This chapter gives an introduction of the experimental techniques and the analysis of the observed signals. Special attention is paid to excited-state intramolecular proton transfer (ESIPT) as a prototype example for fast photoinduced tautomeric reactions. Detailed insight into the reaction coordinate is gained from the analysis of the wavepacket motion. Branching reaction channels and the internal conversion taking place after the proton transfer are also considered.