Picosecond Dynamics Features of Electronic Excitations in Gold Nanorods

We study the electronic excitation dynamics in ensembles of plasmonic gold nanorods (Au NRs), in view of the femtosecond transient absorption spectroscopy, and compare the results with the excitation dynamics of spherical Au nanoparticles (NPs). We use the obtained kinetics of the transient absorption of Au NRs and Au NPs to fit the theoretical profile of the temperature relaxation of the excitation dynamics of electron and lattice nanoparticles, as well as their environment under the excitation by laser pulses with duration of 150 fs. For gold nanorods, the electron-phonon interaction constant reads gamma(NRs) = 12 center dot 10(16) W center dot m(-3)center dot K-1, and the heat loss is h(NRs) = 16 center dot 10(8) W center dot m(-2)center dot K-1. In the case of gold nanospheres, the constants are gamma(NPs) = 7 center dot 10(16) W center dot m(-3)center dot K-1 and h(NRs) = 8 center dot 108 W center dot m(-2)center dot K-1, respectively.