Experimental observation of two-photon photoelectric effect from silver aerosol nanoparticles
New Journal of Physics
We report on the observation of two-photon electron emission from silver nanoparticles suspended in nitrogen flow resulting from irradiating them with continuous wave and pulsed laser light with photon energies below the threshold of the single-photon photoelectric effect. The photoelectron yield is quadratic in the light intensity, and the two-photon electron emission threshold is evident. The efficiency of the two-photon photoelectric effect is determined for nanoparticles of various sizes.
... of various sizes. These experiments offer the net information on nonlinear quantum properties of an isolated single nanoparticle which is crucial for developing theoretical models. The phenomenon of the single-photon photoelectric effect ignited the development of the quantum theory of atoms, molecules, and condensed matter  . Detailed experimental studies of this fundamental phenomenon were performed already in the first half of 20th century. The studies of photoelectric effect on aerosol particles appeared much later, a quarter of century ago -  . The importance of this effect on aerosols is clear, because charged particles play an important role in the atmosphere (for example, lightning, ball lightning, corona discharges and losses of electricity on high-power transmission lines). The threshold nature of the single-photon photoelectric effect limits its use at long wavelengths; however, electron photodetachment is