Quadrupole Mode in the Extinction and Elastic-Scattering Spectra of Gold Microstructures

摘要

The quadrupole mode and the retardation-broadened, wavelength-shifted dipole mode have been observed in the extinction and elastic-scattering spectra of two-dimensional arrays of Au microstructures immersed in air, water, and toluene. The electron-beam lithographically produced Au microstructures, resembling hemispheres with radius approx. 100 nm, were arranged in a square lattice with a center-to-center separation of 500 nm and situated on a 5-nm-thick layer of Cr coated on an optically flat quartz substrate.