Nonlinear photoemission from W and Cu investigated by total-yield correlation measurements

Nonlinear photoelectric emission from Cu and W is investigated by subpicosecond laser pulses. Using a pump and probe technique, total-yield correlation measurements are obtained without space-charge saturation. The effects of the heating of the conduction electrons induced by the laser pulses are shown, considering the peak to background contrast ratio of the experimental correlation trace. The present analysis clarifies the consequences of a transient nonequilibrium temperature difference between electrons and the lattice on the correlation trace, confirming for W the presence of a thermally assisted photoemission mechanism.