We investigate the nonlinear optical response of thin gold films with an unprecedented combination of high temporal resolution ($\sim$15 fs) and broad spectral coverage. We quantitatively model the data without free parameters using an extended version of the two-temperature model. Our combined experimental and theoretical approach allows tracking the evolution from a purely nonthermal electron distribution towards a fully thermalized one. These results pose the basis for better understanding of light-matter interaction in metals on the ultrafast time scale.

• Received 23 May 2012

DOI:https://doi.org/10.1103/PhysRevB.86.155139