Plasma resonance in granular deposits and rough surfaces of magnesium

Abstract

An optical study was made of granular deposits and rough surfaces of magnesium, prepared under ultrahigh vacuum, between 1 and 6 eV. The structure of these deposits was determined in situ, using replication techniques. It was shown that discontinuous deposits display plasma resonances of conduction electrons for $\hslash \omega \le 5.12$ eV. Continuous rough deposits do not exhibit these resonances but show a substantial dip in the reflectance at an energy close to that of the surface-plasmon energy. This dip was explained by means of Elson and Ritchie's quantum theory on the influence of roughness on scattering.