ULTRAFAST STUDY OF ELECTRON-PHONON COUPLING IN COLLOIDAL GOLD PARTICLES

The hot electron dynamics in 11 +/- 2 nm diameter Au particles has bee n examined by transient absorption and bleach recovery measurements. T hese experiments show that the timescale for energy relaxation by elec tron-phonon coupling decreases as the pump laser power decreases, and that the relaxation time is independent of the pump or probe wavelengt h at low pump power. The electron-phonon relaxation time measured in o ur experiments (similar to 650 fs) is very similar to the time constan t obtained from experiments with bulk gold samples. These observations are explained using the two-temperature model for electron-phonon cou pling. (C) 1998 Elsevier Science B.V.