Structure in theLII,IIIAbsorption 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 ($\gamma$-alumina) ${\mathrm{Al}}_2$ ${\mathrm{O}}_3$. The spectra were obtained in high resolution (0.06 Å), 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±0.05 Å and 170.49±0.05 Å. This new value for the $L_{\mathrm{III}}$ edge can be combined with recent accurate determinations of the $K{\alpha }_1$ 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±0.15 Å for the amorphous form and 160.15±0.15 Å for the $\gamma$-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 $\gamma$-alumina (with maxima at 78.0, 78.6, 79.5, 84, and 99 eV) is reported here for the first time.