Direct measurements of femtosecond energy dissipation processes of hot electrons in a gold film

Energy dissipation processes of hot electrons in a gold thin film were measured by a femtosecond time-resolved transient reflecting grating method. The processes were analyzed using the two-temperature model and the theory of the transient grating method. It was found that the electron-phonon coupling and thermal diffusion processes could be investigated independently. Temperature dependence of the electron-phonon coupling factor and the thermal conductivity was investigated quantitatively. The results suggested that the nonthermal states of hot electrons still contribute to the dissipation processes on time scales of several picoseconds.