Optical properties of spherical gold mesoparticles.

Optical properties of spherical gold particles with diameters of 150-650 nm (mesoparticles) are studied by reflectance spectroscopy. Particles are fabricated by laser-induced transfer of metallic droplets onto metal and dielectric substrates. Contributions of higher multipoles (beyond the quadrupole) in the scattering spectra of individual spherical particles are experimentally observed. These observations are performed for particles in a homogeneous environment and for particles located in air on a metal surface. Good agreement between calculations on the basis of Mie theory and experimental results obtained in homogeneous environment is demonstrated. Multipole resonance features in the experimental reflection spectra of particles located on a gold substrate, in the wavelength range of 500-1000 nm, are discussed and theoretically analyzed on the basis of finite-difference time-domain simulations. High-resolution Raman images of mesoparticle pairs at different polarizations of light are also presented. [ABSTRACT FROM AUTHOR]