Abstract

Due to their small size, metal nanoparticles are expected to show confined vibrational modes with discrete frequencies. In fact, time-resolved optical pump-probe experiments on metal nanoparticles have revealed periodic signal modulations with frequencies consistent with the lowest (n = 1) vibrational breathing (l = 0) mode [1]. Higher (n > 1) vibrational modes have not been observed, presumably due to their smaller vibration amplitudes. The vibrations in these experiments have been argued to be excited by the thermal expansion of the particle following the lattice heating by the pump laser pulse [1].

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