Picosecond laser pulses are used to sequentially heat and probe the thermally induced reflectivity transients in copper, and the nonequilibrium heating of electrons to a temperature above that of the lattice is observed. The ability to temporally resolve electronic and lattice heating contributions is of considerable significance to thermomodulation spectroscopy of solids.

• Received 26 September 1983

DOI:https://doi.org/10.1103/PhysRevLett.51.2140