Improved Drude-Lorentz dielectric function for gold nanospheres

There is an ever-increasing body of research in applying the Localized Surface Plasmon Resonance (LSPR) of gold nanospheres for applications in the visual part of the electromagnetic spectrum. An important aspect of this work is the accurate representation of the dielectric function for nanospheres with diameters less than the mean free path of the conduction electrons in the bulk material. This paper describes the development of a modified Drude-Lorentz dielectric functions for bulk gold, and for nanosphere. The models are validated against previously published experimental work and are shown to be valid for spheres of diameters of greater than 10 nm.