Browsing by Author "ROJAS, R"
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- ItemCORRELATION AND MULTIPOLAR EFFECTS IN THE DIELECTRIC RESPONSE OF PARTICULATE MATTER - AN ITERATIVE MEAN-FIELD THEORY(1991) CLARO, F; ROJAS, RA systematic approach for treating correlations and multipolar effects in particulate matter is proposed. The method consists of an iterative extension of the Maxwell-Garnett (MG) mean-field approach. The first iterate beyond MG that involves up to three-particle correlations is solved fully to all multipolar orders using Kirkwood's superposition approximation and yields a simple improved formula for the composite dielectric constant at low filling. We find that at 5% filling resonances that originate in multipolar couplings carry about 6% of the total strength. Our results reproduce accurately low-density measurements on pure argon.
- ItemELECTROMAGNETIC RESPONSE OF AN ARRAY OF PARTICLES - NORMAL-MODE THEORY(1986) ROJAS, R; CLARO, F
- ItemNOVEL LASER-INDUCED INTERACTION PROFILES IN CLUSTERS OF MESOSCOPIC PARTICLES(1994) CLARO, F; ROJAS, R
- ItemTHEORY OF SURFACE ENHANCED RAMAN-SCATTERING IN COLLOIDS(1993) ROJAS, R; CLARO, FWe present a theory of surface enhanced Raman scattering (SERS) that gives a response enhancement of up to ten orders of magnitude for pyridine on silver. The signal obtained depends on the laser frequency and is consistent with available experimental data. Our theory emphasizes the effect of the molecule itself on the polarization of the environment as well as the effect of high multipoles, required by the nonuniformity of the local fields. The host could be metallic or insulating. We explain the laser frequency dependence of the relative size of Raman signals for different vibrational lines and predict the presence of a doublet at each electromagnetic resonance. The effect on the Raman signal of depositing a metallic or an oxide coating over a metallic host is discussed.