  Gold nanorod has generated great research interest due to its tunable
longitudinal plasmon resonance. However, little progress has been made in the
understanding of the effect. A major reason is that, except for metallic
spheres and ellipsoids, the interaction between light and nanoparticles is
generally insoluble. In this paper, a new scheme has been proposed to study the
plasmon resonance of gold nanorod, in which the nanorod is modeled as an LC
circuit with an inductance and a capacitance. The obtained resonance wavelength
is dependent on not only aspect ratio but also rod radius, suggesting the
importance of self-inductance and the breakdown of linear scaling. Moreover,
the cross sections for light scattering and absorption have been deduced
analytically, giving rise to a Lorentzian line-shape for the extinction
spectrum. The result provides us with new insight into the phenomenon.
