Optical Constants of Silicon in the Extreme Ultraviolet Region

The optical constants $n$ and $k$ of a single crystal of silicon were determined by measurements of the reflectance at two angles of incidence in the region 10 to 19.2 eV. Energies of plasma oscillation derived from the optical data agree with the values from the electronic energy loss experiments, being about 17 and 11 eV for the normal (or bulk) plasmon and the tangential (or surface) plasmon, respectively.