Triplet state solvation dynamics: Basics and applications

Applying solvation dynamics experiments to viscous liquids or glassy materi als near their glass transition involves long lived triplet probes, whose t ime dependent phosphorescence signals depend upon the local dipolar orienta tional dynamics, mechanical responses, and polarities. The current understa nding of experimental results regarding steady state and time dependent opt ical line shapes and positions is reviewed with emphasis on the relation to the macroscopic dielectric properties. Several applications are discussed in detail, where advantage is taken of the spatially local instead of ensem ble averaging character of this technique. These examples include studies o f dynamical heterogeneity, rotational solute/solvent coupling, secondary re laxations in the glassy state, as well as confinement and interfacial effec ts. (C) 2000 American Institute of Physics. [S0021-9606(00)52043-1].