Anomalous photoemission from Ag(100) in the femtosecond regime

Abstract

We investigate the nonlinear photoemission from a silver monocrystal with femtosecond laser pulses in a wide range of photon energies $(0.8\mathrm{eV}<h\ensuremath{\nu}<6.3\mathrm{eV}).$ Electrons with high kinetic energy are observed in all cases of nonlinear photoemission and at intensities much smaller than $1{\mathrm{G}\mathrm{W}/\mathrm{c}\mathrm{m}}^{2}.$ In the infrared, the electron distribution resembles a decreasing exponential, the tail extending up to tens of eV. At $h\ensuremath{\nu}=3.1\mathrm{eV}$ such exponential distribution coexists with the Fermi-Dirac distribution due to two-photon emission. An explanation in terms of nanosize protuberancies, heated by localized surface plasmons cannot be ruled out, but alternative pictures, however speculative, are worth being considered.