X-RAY-ABSORPTION NEAR-EDGE STRUCTURE OF SINGLE-CRYSTAL SAPPHIRE USING SYNCHROTRON-RADIATION - THE INTERATOMIC-DISTANCE CORRELATION

The high-resolution Al L-edge X-ray absorption near edge structure (XANES) from a single-crystal sapphire sample has been recorded using the total-electron yield (TEY), X-ray fluorescence yield (XFY), and recombination luminescence excitation spectrum (RLES) utilizing synchrotron radiation. There is a very clear splitting of the Al L2 and L3 components (78.38 eV and 78.80 eV) in those spectra. To our knowledge, this is the first report on the Al L23 doublet splitting of single-crystal sapphire obtained from the total-electron yield measurement. All the spectra show similar structure, while the main feature of the RLES is an anticorrelated behavior relative to the TEY and XFY. The edge structures up to 11 eV from the L23 absorption edge are interpreted as due to transition of electron to empty levels of Al ion according to molecular-orbital calculations on the [AlO6]-9 molecules as determined by Balzarotti et al. The post-edge features between 11-60 eV above the Al L23 absorption edge were found to correlate very well with the interatomic distances from the absorbing atom to a neighboring atom as predicted by multiple scattering model of Bianconi and Natoli.