Direct Nonvertical Interband and Intraband Transitions in Al

Abstract

Electron-energy-loss spectra of epitaxial Al foils of {110} orientation show previously unobserved structures between 1.5 and 10 eV for the momentum transfer $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}$ in directions $〈100〉$, $〈110〉$, and $〈111〉$. For $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}\ensuremath{\parallel}〈100〉$, this structure may be consistently interpreted within the essential features of the nearly-free-electron-band structure. Interband transitions show a marked influence on the plasmon dispersion for small $k$; only for $k>0.75$ ${\mathrm{\AA{}}}^{\ensuremath{-}1}$ may it be discussed within the jellium model.