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 meas ured by a femtosecond time-resolved transient reflecting grating method. Th e processes were analyzed using the two-temperature model and the theory of the transient grating method. It was found that the electron-phonon coupli ng and thermal diffusion processes could be investigated independently. Tem perature dependence of the electron-phonon coupling factor and the thermal conductivity was investigated quantitatively. The results suggested that th e nonthermal states of hot electrons still contribute to the dissipation pr ocesses on time scales of several picoseconds.