Angular dependence of dipole scattering cross section: Surface-plasmon losses on Ag(100)

Abstract

We report high-resolution angular-resolved electron-energy-loss measurements of the cross section of surface-plasmon excitation. The intensity shows a pronounced minimum as a function of exchanged momentum near qw ""0 whose position depends on impact energy and angle of incidence of the electron beam and is determined by the value of the phase shift occurring in the scattering process. The effect has been taken into account in the determination of energy and dispersion of the surface plasmon of Ag(100). A linear dispersion is found in the range of qw between 0 and 0.15 A" 1 in contrast to the quadratic behavior found for Ag(l 11) and Ag(l 10). (Academic, New York, 1982). 2 ! H. Ibach and D. L Mills, Electron Energy Loss Spectroscopy and Surface Vibrations

Theory of surface plasmons and surface-plasmon polaritons

“…The surface-plasmon energy dispersions obtained from these spectra are exhibited in Fig. 19 together with the experimental measurements [109]. This figure shows that the trend obtained for the different crystal orientations is in qualitative agreement with the data.…”

“…18 yields ω ′ s = 3.62 eV, only slightly below the energy 3.7 eV of the measured Ag surface plasmon [109].…”

“…Significant deviations from the dispersion of surface plasmons at jellium surfaces occur on the noble metal Ag [107,108,109,110], and the transition metals Hg [111] and Pd [297] (see Table IV). These deviations are mainly due to the presence in these metals of filled 4d and 5d bands, which in the case of Ag yields an anomalous positive and strongly crystal-face dependent dispersion.…”

“…Significant deviations from the dispersion of surface plasmons at jellium surfaces occur on Ag [107,108,109,110] and Hg [111], due to the presence of filled 4d and 5d bands, respectively, which in the case of Ag yields an anomalous positive dispersion. In order to describe the observed features of Ag surface plasmons, various simplified models for the screening of d electrons have been developed [112,113,114,115,116].…”

Plasmons in nanoscale and atomic-scale systems

“…For simple s-electron metals such as Na and K, the induced charge is located outside the metal surface and the dispersion curve exhibits a negative slope in the long-wavelength limit. For d-electron metals, the induced charge is located inside the metal surface and exhibits a positive slope [36,37].…”