Electron dynamics in chromium probed with 20-fs optical pulses

Electron excitation and relaxation in chromium are probed with 20-fs time resolution using an ultrafast optical technique. We obtain good fits to the data for the transient reflectivity and transmittivity changes in a thin film using a simple model of electron relaxation, suggesting the existence of an efficient electron-electron thermalization process on ultrashort-time scales. Quantitative analysis allows the extraction of thermo-optic coefficients and dielectric constant variations related to both the electron and the lattice temperatures.