DISCRETE DIPOLE APPROXIMATION FOR CALCULATING EXTINCTION AND RAMAN INTENSITIES FOR SMALL PARTICLES WITH ARBITRARY SHAPES

We present a discrete dipole approximation (DDA) method to determine e xtinction and Raman intensities for small metal particles of arbitrary shape. The Raman intensity calculation involves evaluation of surface electromagnetic fields, and thus is relevant to surface enhanced Rama n scattering (SERS) intensities. We demonstrate convergence of the met hod by considering light absorption and scattering from an isolated sp heroid, from an isolated tetrahedron, from two coupled spheroids, and from a spheroid on a flat surface. We also examine comparisons with tr aditional T-matrix methods. Extensions and simplifications of the meth od in studies of clusters and arrays of particles are presented. (C) 1 995 American Institute of Physics.