MAPPING THE EXCITED-STATE BANDS ABOVE THE VACUUM LEVEL WITH VLEED - PRINCIPLES, RESULTS FOR CU, AND THE CONNECTION TO PHOTOEMISSION

Experimental photoelectron spectra are usually interpreted using rathe r crude approximations for the upper states into which the electrons a re excited. Better knowledge about these excited states could substant ially improve the accuracy of valence band mapping by photoelectron sp ectroscopy. We here demonstrate that VLEED measurements are ideally su ited for accurate determination of the desired upper states. This is i llustrated by model calculations including absorption and self-energy corrections. The close correspondence between so-called irregularity p oints of the excited-state bands and the total electron reflectivity i s established, which opens up the possibility for direct mapping of ir regularity points by comparison with experimental VLEED spectra, and f or fitting of the whole excited-state bands between these points. The proposed scheme is finally used to determine the excited-state bands o f Cu along Gamma L from measurements on Cu(111).