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Progress In Electromagnetics Research | ISSN: 1070-4698, E-ISSN: 1559-8985 |

Home > Vol. 98 > pp. 97-118
## PLASMONS AND DIFFRACTION OF AN ELECTROMAGNETIC PLANE WAVE BY A METALLIC SPHEREBy M. Apostol and G. Vaman
Abstract:
The di®raction of a plane electromagnetic wave by an ideal metallic sphere (Mie's theory) is investigated by a new method. The method represents the charge disturbances (polarization) by a displacement field in the positions of the mobile charges (electrons) and uses the equation of motion for the polarization together with the electromagnetic potentials. We employ a special set of orthogonal functions, which are combinations of spherical Bessel functions and vector spherical harmonics. This way, we obtain coupled integral equations for the displacement field, which we solve. In the non-retarded limit (Coulomb interaction) we get the branch of "spherical" (surface) plasmons at frequencies ω = ω _{p}sqrt(l/(2(l/ + 1)), where ω_{p} is the (bulk) plasma frequency and l = 1, 2,.... When retardation is included, for an incident plane wave, we compute the field inside and outside the sphere (the scattered field), the corresponding energy stored by these fields, Poynting vector and scattering cross-section. The results agree with the so-called theory of "effective medium permittivity", although we do not start the calculations with the dielectric function. In turn, we recover in our results the well-known dielectric function of metals. We have checked the continuity of the tangential components of the electric field and continuity of the normal component of the electric displacement at the sphere surface, as well as the conservation of the energy flow and re-derived the "optical theorem". In the limit of small radii (in comparison with the electromagnetic wavelength) the sphere exhibits a series of resonant absorptions at frequencies close to the plasmon frequencies given above. For large radii these resonances disappear.
2. Van De Hulst, H. C., 3. Doyle, W. T. and A. Agarwal, "Optical extinction of metal spheres," 4. Crowell, J. and R. H. Ritchie, "Radiation decay of Coulomb-stimulated plasmons in spheres," 5. Ashkin, A. and J. M. Dziedzic, "Observation of resonances in the radiation pressure on dielectric spheres," 6. Chylek, P., J. T. Kiehl, and M. K. W. Ko, "Narrow resonance structures in the Mie scattering characteristics," 7. Conwell, P. R., P. W. Barber, and C. K. Rushforth, "Resonant spectra of dielectric spheres," 8. Marston, P. L. and J. H. Crichton, "Radiation torque on a sphere caused by a circularly-polarized electromagnetic wave," 9. Chang, S., J. T. Kim, J. H. Jo, and S. S. Lee, "Optical force on a sphere caused by the evanescent field of a Gaussian beam; Effects of multiple scattering," 10. Ruppin, R., "Optical properties of small metallic spheres," 11. Messinger, B. J., K. U. Von Raben, R. K. Chang, and P. W. Barber, "Local fields at the surface of noble-metal microspheres," 12. Arnold, S., A. B. Pluchino, and K. M. Leung, "Influence of surface-mode-enhanced local fields on photophoresis," 13. Brechignac, C., P. Cahuzac, J. Leygnier, and A Sarfati, "Optical response of large lithium clusters: Evolution toward the bulk," 14. Markowicz, P., K. Kolwas, and M. Kolwas, "Experimental determination of free-electron plasma damping rate in large sodium clusters," 15. Brechignac, C., P. Cahuzac, N. Kebaili, J. Leygnier, and H. Yoshida, "Interband effect in the optical response of strontium clusters," 16. Apostol, M. and G. Vaman, "Electromagnetic field interacting with a semi-infinite plasma," 17. Born, M. and E. Wolf, 18. Lorentz, H. A., 19. Apostol, M. and G. Vaman, "Plasmons and polaritons in a semi-infinite plasma and a plasma slab," 20. Apostol, M. and G. Vaman, "Electromagnetic eigenmodes in matter. van der Waals-London and Casimir forces," 21. Edmonds, A. R., 22. Blatt, J. M. and V. E. Weisskopf, 23. Erdelyi, A., 24. Abramowitz, M. and I. A. Stegun, 25. Gradshteyn, I. S. and I. M. Ryzhik, |

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