ИСТИНА

It is shown that light scattering by a non-magnetic nanocluster with low dissipa- tion rate close to plasmon (polariton) resonance frequencies differs from the one described by the Rayleigh approximation dramatically. Thus, a more accurate approach should be employed. In the present contribution the problem is studied within the framework of the exact Mie solution. It is shown that if imaginary part of the dielectric permittivity of the cluster is small enough, the dissipative damping is replaced by the radiative one. In such a case the problem exhibits sharp giant resonances with very unusual properties. In particular, despite smallness of the cluster relative to the incident light wavelength the extinction cross section for these resonances increases with an increase in the order of the resonance, i.e., the cross section at the dipole resonance is smaller than that at the quadrupole resonance, etc. (inverted hierarchy of the resonances); the characteristic values of the electric and magnetic fields inside the cluster and in its immediate vicinity are singular in the cluster size, while the energy circulation in the near-field is rather complicated. The corresponding field of the Poynting vector includes singular points, whose number, types and positions are very sensitive to fine changes in the incident light frequency. As an example a bifurcation diagram, describing the behavior of the singular points in the vicinity of the dipole resonance for a cluster with a certain fixed size is obtained. Practical examples of this scattering for different pairs "nanocluster–host medium" with actual (experi- mentally measured) dispersion relations for dielectric permittivity are presented. The results may provide new opportunities for giant, controlled, highly frequency-sensitive enhancement and variation of electromagnetic field at nano-scales.