Electron-electron and electron-phonon thermalization processes are inv
estigated in gold films using a high-sensitivity multiple-wavelength f
emtosecond pump-probe technique. A nonequilibrium electron distributio
n is excited by free-carrier absorption of an infrared femtosecond pul
se and its relaxation dynamics followed by measuring the transient ref
lectivity and transmissivity with a visible probe pulse. Measurements
performed in a thin gold film in the very low perturbation limit (DELT
AT(e) approximately 20 K) yield evidence for the existence of a non-Fe
rmi electron distribution with an electron thermalization time of appr
oximately 500 fs and an electron-lattice interaction time of 1 ps. The
apparent thermalization dynamics of the electron gas is much faster i
n optically thick samples and is shown to be dominated by transport ef
fects.