Direct Nonvertical Interband and Intraband Transitions in Al

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 $\overrightarrow{\mathrm{k}}$ in directions $〈100〉$, $〈110〉$, and $〈111〉$. For $\overrightarrow{\mathrm{k}}\parallel 〈100〉$, 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 $k>\mathrm{}0.75\mathrm{}$ ${\mathrm{\AA }}^{-1\mathrm{}}$ may it be discussed within the jellium model.