CORE-LEVEL SHIFTS IN AMORPHOUS TRANSITION-METAL TIN ALLOYS

X-ray and UV photoemission data are presented for core level binding e nergy shifts in amorphous TM-Sn (TM = Fe, Co, Ni, Pd) films prepared i n situ at low temperature by means of a vapour quenching technique. Th e experimental results are compared to predictions based on the thermo dynamical model of Martensson and Johansson using the Born-Haber cycle and the equivalent core approximation. The overall good agreement fou nd between theory and experiment emphasizes the strong influence of th e conduction electrons in the photoionization process. It is observed that relaxation effects and screening of the final core hole state can result in binding energy shifts of the same order of magnitude as tho se of the ground state due to alloying. As a consequence, photoemissio n core level binding energies in amorphous alloys generally cannot be interpreted within the ground state picture, but have to be corrected for final state contributions.