ultrafast depolarization of transient absorption as a probe of plasmonicity of optical transitions in ag nanoclusters

Time-resolved polarization-dependent transient absorption has been used to study the plasmonicity of the optical transitions of ag nanoparticles and nanoclusters. the lack of a measureable polarization anisotropy in the nanoparticles is indicative of the ultrafast electron-electron scattering while the anisotropy with a depolarization timescale of 500 fs observed in the nanoclusters indicates the excitation of a non-plasmonic state. the short lifetime of the anisotropy is a measure of electronic coupling between nearly degenerate states and is thus proposed as a sensitive measurement of the plasmonic content of the optical transitions of nanoclusters.