Photoexcited Triplet State Kinetics Studied by Electron Paramagnetic Resonance Spectroscopy.

Following the first evidence of the triplet character of the optically excited phosphorescent state of naphthalene by Hutchison and Mangum in 1958, electron paramagnetic resonance (EPR) spectroscopy has become widely used to study and understand the properties and kinetic characteristics of excited triplet states. This minireview gives an overview over EPR techniques based on continuous microwave methods using lock-in or direct detection as well as pulsed EPR methods with respect to their suitability for kinetic studies of excited triplet states. A short historical overview of the experimental and theoretical developments in this field of research as well as of the triplet systems studied, with a final focus on fullerenes, is given. This may help newcomers to the field as a guide to the relevant literature.