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The resonance frequency of an electric dipole placed near a conducting surface is shifted by the dipole-surface interaction. This Letter reports the observation and measurement of these shifts at optical frequencies for an experimental system that consists of a metal island film spaced a distance d from a continuous Ag film. The dependence of the shift in the frequency of the island resonance on d shows good agreement with that predicted by a classical theory of the dipole-surface interaction. PACS numbers: 71.36.+c, 73.60.Dt The interaction between electromagnetic radiation and an electric dipole is a fundamental process in physics. When the dipole is placed within a few wavelengths of a conducting surface, the major features of the interaction are changed from those observed for an isolated dipole. Experiments at optical frequencies have demonstrated (1) the strong dependence of the molecular fluorescent decay rate on the separation between a molecule and a metal surface, ' (2) the transfer of energy between molecular dipoles and surface plasmons on the metal surface, 2~a nd (3) the ability of the dipole-surface interaction to enhance the strength of such processes as molecular Raman scattering5 and molecular fluorescence. 6 In addition to these three effects, theoretical treatments of the problem also predict the existence of a shift in the dipole's resonance frequency.~' 2 This frequency shift is a universal feature of the dipole-surface interaction and, in simple terms, results from the coupling between the dipole and its own image in the metal surface.In spite of the fact that these frequency shifts should appear for both microscopic and macroscopic dipoles, there have been no reports of their observation, perhaps because their magnitudes are predicted to be quite small for the typical metalmolecule system as a result of the narrow linewidths associated with molecular resonances. 8 This Letter reports the results of opticalfrequency experiments on a dipole-metal system that exhibits resonance-frequency shifts that we attribute to the dipole-surface interaction. The observation of these shifts is significant because it confirms a previously untested feature of the theory, and because it reveals an important aspect of a class of sample geometries of widespread interest in the study of surface phenomena. Our sample geometry is shown in Fig. 1 and consists of a three-layer structure deposited on a glass substrate. First, a continuous silver film of thickness 50 nm was evap--substratẽ OOO~A g LiF Ag islond film FIG. 1. Cross section of three-layer sample geometry used in the present experiment. The continuous silverfilm has a thickness of 50 nm. The thickness of the LiF spacer layer, d, was varied between 5 and 80 nm. The silver island film had a mass thickness of 3 nm, orated onto a glass substrate. After partial masking with a movable shutter, a lithium fluoride (LiF) spacer layer of thickness d was deposited over a portion of the silver surface. Further masking preceded the slow (0.5 A/sec) deposition of e...

This paper describes the global ocean component of the NCAR Climate System Model. New parameterizations of the effects of mesoscale eddies and of the upper-ocean boundary layer are included. Numerical improvements include a third-order upwind advection scheme and elimination of the artificial North Pole island in the original MOM 1.1 code. Updated forcing fields are used to drive the ocean-alone solution, which is integrated long enough so that it is in equilibrium. The ocean transports and potential temperature and salinity distributions are compared with observations. The solution sensitivity to the freshwater forcing distribution is highlighted, and the sensitivity to resolution is also briefly discussed.

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