Photophysics of Metal Nanoparticles: Heat Dissipation and Coherent Excitation of Phonon Modes

Ultrafast laser excitation of metal nanoparticles can create temperature increases of many hundreds of Kelvin. The aim of this paper is to provide an overview of our recent experimental studies of heat dissipation and the coherent generation of acoustic phonon modes in the particles. Our results show that the rate of heat dissipation depends on the surface area of the particles, and that both impulsive lattice heating and hot-electron pressure contribute to phonon excitation. The measured periods also depend on the pump laser intensity: higher intensities yield slower periods. This softening of the coherently excited phonon modes is due to the temperature dependence of the elastic constants of the particles.

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