The sudden absorption of light by a metal nanoparticle launches a series of relaxation processes (internal thermalization, acoustic vibrations, and cooling) which induce a transient modification of its optical response. In this work, the transient optical response associated with the internal thermalization of a single gold nanodisk (occurring on a few picoseconds time scale) was quantitatively investigated by time-resolved spectroscopy experiments, and the measured signals were compared with a model accounting for the effects of both electron and ionic lattice heating. We show that experimental time-resolved signals at delays posterior to nanodisk excitation and electron gas thermalization can be simply interpreted as a combination of electron and lattice temperature evolutions, with probe wavelength-dependent weights. This demonstrates the possibility to selectively probe the electronic or lattice dynamics, through the choice of specific probe wavelengths. Additionally, the time-dependent spectral shape of transient extinction cross-section changes is shown to be successively dominated by the effects of electron and lattice heating, which present distinct spectral signatures.
Electron and Lattice Heating Contributions to the Transient Optical Response of a Single Plasmonic Nano-Object / Rouxel, R.; Diego, M.; Maioli, P.; Lascoux, N.; Vialla, F.; Rossella, F.; Banfi, F.; Vallee, F.; Del Fatti, N.; Crut, A.. - In: JOURNAL OF PHYSICAL CHEMISTRY. C. - ISSN 1932-7447. - 125:42(2021), pp. 23275-23286. [10.1021/acs.jpcc.1c06629]