ANGLE-RESOLVED PHOTOEMISSION THEORY FOR VALENCE-ELECTRONS .1. A CALCULATION SCHEME BY THE MULTISLICE METHOD

A one-step photoemission calculation scheme for valence electrons is p resented which uses (to construct the initial- and final-state wavefun ctions) the multi-slice technique, which has been developed for Low-en ergy electron diffraction (LEED). Included in the scheme is the possib ility of having an over-layer or an arbitrarily shaped surface barrier , and realizing both the electron and hole life-times by means of an i maginary part to the energy. The photoemission intensity due to surfac e states can also be calculated separately by the same procedure. The advantage of the scheme is that because the crystal potential is divid ed into arbitrarily thin slices, problems associated with the frequent ly used muffin-tin potential do not arise.