Femtosecond nonlinear optical spectroscopy of the acoustic vibration of metal nanoparticles under high pressure

A time-resolved femtosecond optical pump-probe setup has been combined with a high hydrostatic pressure apparatus to investigate the pressure dependence of the electron and lattice ultrafast response of silver nanoparticles embedded in a glass. The short time scale measurements shows that the time constant of the electron-phonon energy exchange is unchanged over the studied pressure range (up to 60 kbar). The frequency of the coherent acoustic vibration of the nanoparticles observed on a longer time scale is found to linearly increase with pressure in agreement with the metal elastic property changes. The acoustic mode damping is also found to be modified by pressure, suggesting alteration of the metal-glass interface properties.