Spectral properties and relaxation dynamics of surface plasmon electronic oscillations in gold and silver nanodots and nanorods

The field of nanoparticle research has drawn much attention in the past dec ade as a result of the search for new materials. Size confinement results i n new electronic and optical properties, possibly suitable for many electro nic and optoelectronic applications. A characteristic feature of noble meta l nanoparticles is the strong color of their colloidal solutions, which is caused by the surface plasmon absorption. This article describes our studie s of the properties of the surface plasmon absorption in metal nanoparticle s that range in size between 10 and 100 nm. The effects of size, shape, and composition on the plasmon absorption maximum and its bandwidth are discus sed. Furthermore, the optical response of the surface plasmon absorption du e to excitation with femtosecond laser pulses allowed us to follow the elec tron dynamics (electron-electron and electron-phonon scattering) in these m etal nanoparticles. It: is found that the electron-phonon relaxation proces ses in nanoparticles, which are smaller than the electron mean free path, a re independent of their size or shape. Intense laser heating of the electro ns in these particles is also found to cause a shape transformation (photoi somerization of the rods into spheres or fragmentation), which depends on t he laser pulse energy and pulse width.