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Multipole response of metal spheres to q-dependent excitation operators Serra, Llorenç Garcias, Francisca Barranco Gómez, Manuel Barberán Falcón, Núria Navarro Faus, Jesús Física de l'estat sòlid Electrònica quàntica Solid state physics Quantum electronics We have obtained the once and thrice energy-weighted moments of the random-phase-approximation (RPA) response to q-dependent excitation operators of type j L (qr) Y L 0 for metal spheres described within a spherical jellium model. These two moments, in conjunction with the Thomas-Fermi estimation of the RPA inverse energy-weighted moment, are used to study the response of these systems as a function of q. For small values of q, we recover the surface-mode systematics, whereas for large q’s the response is mainly determined by electron-hole excitations. For intermediate q values, bulk oscillations are found and their connection with the hydrodynamical-model predictions is established. In the limit of a big sphere, we have obtained an improved bulk-plasmon pole approximation for the dispersion relation which includes in a very easy way exchange and correlation effects. We have found that these corrections are not negligible. The moments of the response corresponding to a plane wave e i q ⋅ r are also discussed. Numerical applications to the case of Na spheres whose ground-state structure is described by models of different complexity (constant electronic density, Thomas-Fermi or Kohn-Sham) are presented. 2009-10-22T10:15:19Z 2009-10-22T10:15:19Z 1990 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 0163-1829 https://hdl.handle.net/2445/9763 43611 eng Reproducció digital del document publicat en format paper, proporcionada per PROLA i http.//dx.doi.org/10.1103/PhysRevB.41.3434 Physical Review B, 1990, vol. 41, núm. 6, p. 3434-3446. https://doi.org/10.1103/PhysRevB.41.3434 (c) The American Physical Society, 1990 info:eu-repo/semantics/openAccess 13 p. application/pdf The American Physical Society Articles publicats en revistes (Física Quàntica i Astrofísica)