Low-frequency absorption of electro-magnetic radiation in thin metallic films

We study the absorption of low-frequency radiation in thin metallic films with ballistic electron dynamics. Incorporating screening effects, we calculate an approximation to the effective potential inside the film using a quasi-classical approach. This approach combined with Fermiʹs golden rule is used to derive an analytical formula for the absorption coefficient valid for frequencies much smaller than the plasma frequency, and high electron densities.