Structure in the L I I , I I I Absorption of Aluminum and its Oxides

The ${L}_{\mathrm{I}\mathrm{I},\mathrm{I}\mathrm{I}\mathrm{I}}$ region of absorption has been observed for thin films of evaporated aluminum, for amorphous (anodized) ${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$, and for crystalline ($\ensuremath{\gamma}$-alumina) ${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$. The spectra were obtained in high resolution (0.06 \AA{}), using the NBS 180-MeV electron synchrotron as a background source. The ${L}_{\mathrm{I}\mathrm{I},\mathrm{I}\mathrm{I}\mathrm{I}}$ absorption edges of Al are located with improved accuracy at 169.49\ifmmode\pm\else\textpm\fi{}0.05 \AA{} and 170.49\ifmmode\pm\else\textpm\fi{}0.05 \AA{}. This new value for the ${L}_{\mathrm{III}}$ edge can be combined with recent accurate determinations of the $K{\ensuremath{\alpha}}_{1}$ emission line to locate also the $K$ absorption edge of aluminum with a significant improvement in accuracy. Structure on the high-energy side of the ${L}_{\mathrm{I}\mathrm{I},\mathrm{I}\mathrm{I}\mathrm{I}}$ edges is compatible with other recent observations. The $L$ absorption edge of Al in ${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$ is not split in high resolution, and is located at 162.11\ifmmode\pm\else\textpm\fi{}0.15 \AA{} for the amorphous form and 160.15\ifmmode\pm\else\textpm\fi{}0.15 \AA{} for the $\ensuremath{\gamma}$-alumina. Both forms show considerable structure on the high-energy side of the edge. That observed for the amorphous form is in agreement with other recent observations, while the absorption structure in $\ensuremath{\gamma}$-alumina (with maxima at 78.0, 78.6, 79.5, 84, and 99 eV) is reported here for the first time.