Analytical approximations of the noble metals dielectric permittivity

In this work, the measured optical constants of a gold, silver, copper and aluminum have been theoretically analyzed. Analytical expressions describing dielectric permittivity of these noble metals in the spectral range from 0.1 to 4 microns were presented on the base of works of McPeac and Babar where the most reliable experimental data are given. The total spectral range is divided into several ranges and the corresponding function was selected for each wavelength range. These functions are preferably in the polynomial form. The selection of the function on each range was carried out by the Heaviside function.