The density response of a metal surface to charge and potential perturbations is derived using a hydrodynamic description of the mobile electrons. Spatial dispersion and Ohmic damping are allowed for and results are found for both the retarded and nonretarded cases. The theory is carried through via three separate schemes: the density response is found from second-quantized density operators, from the effect of an applied potential, and from the effect of applied charge and current sources. The formulas are compared to earlier work. We confirm the nonretarded results of Eguiluz, but not those of others.
A calculational scheme for the electromagnetic fields of a charge moving at constant velocity parallel to a flat conducting slab is developed. The results can be evaluated for arbitrary speed of the charge. Comparisons are made with earlier work that was mostly limited to a low-speed approximation. Both analytic insights and numerical illustrations of the theory are given.
We investigate the collective mode excitation spectrum of an electron gas in a quantum strip that is subjected to a perpendicular magnetic field, with emphasis on the dipole-forbidden transitions. The quantum strip is assumed to be defined in a two-dimensional electron gas by the application of a parabolic confining potential. A classical continuum theory of the collective modes is developed and solved exactly. These results are used to determine the density-response functions. An experimental method to detect the dipole-forbidden modes, based on the use of an asymmetric planar metal grating above an array of quantum strips, is proposed, and calculations of the expected infrared transmission spectrum of the combined grating-strip system are presented. In a system with reasonable parameters, we find that some of the dipole-forbidden absorption peaks are large enough to be observable.
A theoretical estimate is made of the scattering efficiency of x rays by surface and bulk plasmons near a flat metal surface. The density-density correlation function needed by the theory is taken from hydrodynamic theory. At grazing angles of incidence and exit, specifically beyond the critical angle, the surface and bulk-plasmon losses can be of comparable strength. An estimate of their absolute magnitude suggests that they should be experimentally detectable if high-intensity x-ray sources are used. Several model calculations are presented to illustrate the possible spectra.
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