Optical and Photoelectric Properties of Mg in the Vacuum Ultraviolet

Optical and photoelectric measurements on Mg are presented for photon energies from 2 to 12 eV. A minimum in the reflectance at ∼ 7 eV is interpreted in terms of absorption due to the excitation of nonradiative surface plasmons at the rough Mg surface. By fitting the data to a theoretical expression for nonradiative-surface-plasmon excitation, rms surface-roughness heights $\delta$ and autocorrelation lengths $\sigma$ have been obtained. Photoelectric-yield measurements show a strong maximum for photons of ∼ 7 eV, very close to the energy at which the reflectance is a minimum. It is suggested that this peak in the photoelectric yield is due to the decay of nonradiative surface plasmons into one-electron excitations which are observed in the photoemission. In addition to the data below 12 eV, photoelectron energy distributions are presented for photon energies of 13.5 and 14.9 eV. Examination of all the photoelectron energy distributions fails to reveal structure resulting from photoelectrons losing energy by creating surface plasmons while escaping from the surface. If this process occurs in Mg it is overshadowed in our data by electrons that have suffered one or more inelastic electron-electron scattering events.