Core level shifts and valence change at the surface of intermetallic rare-earth systems

Surface effects on valence and 4f as well as 5p binding energies of the dialuminides of the heavy rare earths (RE) including Lu were investigated by high-resolution photoemission using synchrotron radiation. For comparison, Eu, Yb, and Lu metal and YbZn2 were also studied. A divalent surface layer was found for (rivalent SrnAl2. A pronounced difference between trivalent and divalent (including mixed-valent) RE systems in the sensitivity of core-level binding energies to alloying was found and is discussed in terms of the valence-band structure of these solids. © 1983.