Ultrafast dephasing time of localized surface plasmon polariton resonance and the involved damping mechanisms in colloidal gold nanoparticles

In this contribution, for the first time precise in situ measurements of the ultrafast dephasing time T2 of localized surface plasmon polariton resonances in colloidal gold nanoparticles with the objective to identify the involved damping mechanisms are presented. T2 is an essential parameter that does not only allow one to determine the field enhancement factor that is of great importance for many applications of nanoparticles, but also reflects the role of different dephasing mechanisms. The most essential result is the observation of a chemical interface damping which causes a dramatic shortening of the dephasing time. While T2∞ = 9.4 fs can be obtained from the bulk dielectric function, the value shrinks to 3.7 fs if the nanoparticles are in aqueous solution.