Generation of nonequilibrium electron and lattice temperatures in copper by picosecond laser pulses

Picosecond laser pulses can be used to generate and probe nonequilibrium electron and lattice temperature differences in metals. This is demonstrated by transient thermoreflectance measurements on copper in the vicinity of the d-band absorption edge. Our measurements are in agreement with an energy-balance model based on a separation of the one-dimensional heat-flow equation into electron and lattice subsystems.