Optical Studies of Dynamics in Noble Metal Nanostructures

The fundamental optical properties of metal nanoparticles, the dynamics that occur following absorption of photons, are studied. The spectra of metal nanoparticles are dominated by the localized surface plasmon resonance (LSPR) and the position of the LSPR depends on the size and shape of the particles, their composition, and the properties of the environment. Link and co-workers examined nanorods with aspect ratios between 2 and 3, and widths between 30 and 120 nm and observed a significant broadening and red-shifting of the dipolar longitudinal LSPR with increasing width. Transient absorption data for different sized Ag particles taken over a slightly longer time range show that decay in the signal arises from energy loss from the electron distribution because of electron-phonon coupling. The vibrational periods measured in the transient absorption experiments are found to depend on the intensity of the pump laser.