ABSTRACT
By combination of two special methods, i.e., persistent spectral hole burning and laser assisted nanoparticle preparation, the dephasing time T2 of surface plasmon excitation in silver nanoparticles was systematically investigated. A strong dependence of T2 on the plasmon energy is found which reflects the relevance of interband damping and makes necessary a precise control of the particle shape when measuring T2. The influence of the reduced dimension on the dephasing dynamics was observed as a decrease of T2 with shrinking particle size. In addition, for silver nanoparticles on quartz substrates, a considerable amount of chemical interface damping was observed.
ABSTRACT
We describe a new technique to determine the homogeneous linewidths of surface plasmon resonances of metal nanoparticles and thus measure the decay time of this collective electron excitation. The method is based on spectral hole burning and has been applied to supported oblate Ag particles with radii of 7.5 nm. From the experimental results and a theoretical model of hole burning the linewidth of 260 meV corresponding to a decay time of 4.8 fs was extracted. This value is shorter than expected for damping by bulk electron scattering. We conclude that additional damping mechanisms have been observed and reflect confinement of the electrons in nanoparticles with sizes below 10 nm.
