  Arrays of metallic nanoparticles support individual and collective plasmonic
excitations that contribute to unusual phenomena like surface enhanced Raman
scattering, anomalous transparency, negative index, and subwavelength
resolution in various metamaterials. We have examined the electromagnetic
response of dual Kron's lattice and films containing up to three monolayers of
metallic nanospheres. It appears that open cubic Kron's lattice exhibits `soft'
electromagnetic response but no negative index behavior. The close-packed
arrays behave similarly: there are plasmon resonances and very high
transmission at certain wavelengths that are much larger than the separation
between the particles, and a `soft' magnetic response, with small but positive
effective index of refraction. It would be interesting to check those
predictions experimentally.
