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 →k in directions $〈100〉$, $〈110〉$, and $〈111〉$. For →k∥〈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 $k>0.75$ ^-1 may it be discussed within the jellium model.