Experimental evidence of above-threshold photoemission in solids

Phys Rev Lett. 2005 Jan 28;94(3):037601. doi: 10.1103/PhysRevLett.94.037601. Epub 2005 Jan 24.

Abstract

Nonlinear photoemission from a silver single crystal is investigated by femtosecond laser pulses in a perturbative regime. A clear observation of above-threshold photoemission in solids is reported for the first time. The ratio between the three-photon above-threshold and the two-photon Fermi edges is found to be 10(-4). This value constitutes the only available benchmark for theories aimed at understanding the mechanism responsible for above-threshold photoemission in solids.