A Experimental Determination of the Momentum - Dependence of the Aluminum K-Absorption Threshold
The momentum-transfer dependence of the aluminum K-absorption threshold has been investigated using electron -energy-loss spectroscopy. Just above the aluminum K-edge there is additional oscillator strength not explained by any calculation. The data of this thesis, acquired at non-zero scattering angle, provide information relevant to explaining this white line. Several physical processes contribute to the K -edge. It has been suggested in the literature that neglect of one of these processes, the core-hole interaction, is responsible for the observed discrepancy. This process is difficult to incorporate in calculations that include interactions with neighboring atoms. Simple models, with and without the core-hole interaction, however, display different overall dependences on momentum-transfer. The data show a dependence more like the core-hole model than the model with no core-hole. The agreement is not good. A calculation which includes both the core-hole interaction and backscattering from neighbor atoms is needed. Comparison of such a calculation with the data of this thesis will serve as a strong test of the core-hole-interaction hypothesis. Spectra were acquired at large transverse-momentum transfer, up to 8.625 (ANGSTROM)('-1). New methods of removing the effects of multiple scattering were developed to deal with this data.
- Pub Date:
- WHITE LINE;
- MULTIPLE SCATTERING;
- Physics: Condensed Matter