QUANTUM-SIZE EFFECT ON THE OPTICAL-PROPERTIES OF SMALL METALLIC PARTICLES

A simple quantum-sphere model for small metallic particles of arbitrary size embedded in nonabsorbing dielectric media is used to compute the real and imaginary parts of the dielectric function. The quantum confined electrons can be considered as nearly free electrons but having discrete energy levels. The dielectric function contributed from transitions between energy levels is calculated via the momentum transition matrix under the zero-temperature approximation. Consequently, we have derived the size dependence of the absorption spectra which clearly indicate the blueshift and the broadening of the spectra as the particle sizes are reduced. The theoretical simulation is in satisfactory agreement with the experimental data for particle sizes below 10 nm.