Electron Dynamics in Copper Metallic Nanoparticles Probed with Femtosecond Optical Pulses

The thermalization of electrons in copper nanoparticles embedded in glass is investigated using femtosecond pump-probe spectroscopy. The time dependent induced transmission is enhanced near the surface plasmon resonance of the nanoparticles, as opposed to the static one obtained with thermomodulation measurements. In addition, a slowing of the process of electron cooling to the lattice temperature is observed at the plasmon resonance. These observations show the importance of quasiparticle collisions in confined metallic structures.