Ionoluminescence of Al, Cu, and Mo: Optical properties of aluminum

Impact of 10- to 30-keV ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ ions on polycrystalline Al, Cu, and Mo targets induces broad-band light emissions in the photon energy range of 2-6 eV; these emissions emanate from the target. For aluminum the emission is particularly intense, increases linearly with incident beam current, and is invariant in relative shape with projectile energy and angle of incidence. The dominant peak is at a photon energy of 2.4 eV; and a weak shoulder is observed at 3.3 eV. An electron-hole recombination model is shown to account for the general form of the emission band. We also calculate the electron density of states and the complex part of the dielectric constant ${\epsilon }_2$; the energy-band structure based on Ashcroft's Al pseudopotential is presented in tabular form.