Multiphoton k-resolved photoemission from gold surface states with 800-nm femtosecond laser pulses

We measure direct multiphoton photoemission of the Au(111) surface state with 800-nm laser pulses. We observe the parabolic dispersion in the angular distribution of photoelectrons having absorbed between four and seven photons. The k dispersion we measure can be explained in terms of Shockley-state replicas, with a nascent hot electrons distribution at k above the Fermi level. Moderate laser power densities, of the order of 100 GW/cm2 , resulted in large electron yields, indicating the importance of multiphoton excitations to define the electronic and magnetic properties of matter in the first hundred femtoseconds after laser excitation.