Above-threshold multiphoton photoelectric effect of a gold surface Gydz6 Farkas, MEMBER SPIE

Abstract. A discrete structure consisting of peaks separated by hv pho-ton energy was found experimentally in the photoelectron energy spec- trum, when illuminating a gold target surface by relatively long light pulses (approximately nanoseconds) and using moderate (approximately1 20 MW/cm2) intensity of Nd:glass lasers (X = 1 .06 pm). This structurecan be considered as the above-threshold photoeffect (ATP) of metalsurfaces. Its occurrence at surprisingly low laser intensities [which arefour orders of magnitude less than the typical intensity range of the anal-ogous above-threshold ionization (ATI) of atoms] was observed whenthe space charge was considerably eliminated. Subject terms: laser pulses; metal surfaces; multiphoton photoeffect of metals;highly energetic photoelectrons; above-threshold photoeffect.Optical Engineering 32(10), 2476—2480 (October 1993). Tocheck this supposition we clearly demonstrated in ourrecent 2, 1 3 that photoelectron energies above E0up to approximately 600 eV from a polycrystalline gold sur-face, where the photoelectrons are induced by Nd:glass laserpulses (8 p5, 25 GW/cm2). There, however, because of theultrashort duration and the extreme electron density, inter-electronic Coulombic forces occurred, causing space-chargeeffects, which might play an important role. The fast electronswere created mainly by the Coulombic explosion, thereforeeven if ATP peaks existed, Coulombic forces and the laserfluctuation might have hidden them, as was shown in Refs.14