CALCULATED PHOTOEMISSION SPECTRA FROM THE AL(001) SURFACE

We present a theoretical study of photoemission from the Al(001) surfa ce. The purpose of this work is to examine the validity of the nearly- free-electron-gas model for Al, and to study the importance of many-bo dy and surface effects in its photoemission spectra. This is an extens ion of our earlier study on the Na spectra, but the band structure of Al is much more complicated and requires a detailed band calculation. A slab model is employed to self-consistently determine its band-with the inclusion of the self-energy correction. The band states are then used to calculate the photoemission spectra, which are compared with m easurements. Reasonable agreement has been found for the Al bandwidth, and also for the spectral profiles at various photon energies. This r esult strongly supports the view that, once the many-body and surface effects are properly taken into account, the spectra can be well descr ibed with the nearly-free-electron bands-as in the case of Na. Special attention has been paid to surface-state emissions. A resonant enhanc ement in its spectral intensities has been found both in the calculati on and in the measurement. However, there still exist some discrepanci es which call for further studies.