On qualitative analysis of the upper band effects in very-low-energy electron diffraction and photoemission

Experimental very-low-energy electron diffraction (VLEED) and photoemision (PE) bandmapping, particularly for non-free-electron materials, requires to analyze the partial effects of the upper bands composing the total electron state. These effects are related to the partial absorbed currents (PACs) in the VLEED process. I describe a simple method to estimate PACs, using only real-k(perpendicular to) Bloch waves within the no-absorption approximation. The method may thus be implemented on top of any standard bandstructure code at negligible computational cost. The accuracy suffices for qualitative analysis in experimental VLEED and PE. (C) 1998 Elsevier Science Ltd.