The response of gold nanoparticles to excitation with light evolves in a num-
ber of steps. These steps are shown schematically in Fig. 1.10. After excitation
with a laser pulse, the excitation energy is primarily transferred to the elec-
trons and not to the lattice, due to the much smaller heat capacity of the lat-
tice. A part of the electron distribution is excited and the electrons will be set
in a coherent oscillatory motion, which is damped on a 10-fs timescale. The
initial excitation creates a largely non-thermal distribution. Through electron-
electron scattering, the energy is redistributed over the entire electron dis-
tribution within a few hundred femtoseconds. This brings the electrons in
thermal equilibrium and creates a hot electron gas, which will subsequently
release its energy, thereby heating the lattice. The latter process, which is
in fact initiated before the electron gas is completely in equilibrium, takes