Tunneling photoeffect mechanism in metallic nanoparticles activated by cesium and oxygen

The long-wavelength surface-plasmon-induced portion of the photoelectron emission (PE) spectrum of granulated silver and gold films activated by cesium and oxygen is found to shift toward the short-wavelength region with respect to the optical absorption band. The intensity of this long-wavelength portion decreases exponentially with increasing wavelength, and a photoelectric threshold is not detected. The photoeffect in such structures is shown to be determined by the probability of tunneling nonequilibrium photoelectrons through the potential barrier formed by an activating layer. The PE spectra calculated in the triangle barrier approximation agree well with appropriate experimental spectra.