Ponderomotive effects in the femtosecond plasmon-assisted photoelectric effect in bulk metals: Evidence for coupling between surface and interface plasmons

The existence of ponderomotive acceleration effects in the metal bulk has been experimentally demonstrated in the context of the femtosecond plasmon-assisted multiphoton photoelectric effect in metal systems. The resulting electron energy spectra show that these effects essentially depend on the coupling between the surface and interface plasmons. While the essential part played by the ponderomotive force of the surface plasmon is to accelerate the photoelectrons in the vacuum, the dramatic enhancement of the photoelectron production and the angular dependence in the photoemission process mainly result from ponderomotive effects in the metal bulk.