SURFACE CORE-LEVEL SHIFT OF 4F STATES FOR TB(0001)

For Tb(0001), a surface core-level shift of the 4f7 photoemission mult iplet of delta(s)=0.26+/-0.03 eV is determined. This value is by more than a factor of 2 smaller than the result of a recent self-consistent SLAB calculation, but agrees with the prediction of a thermochemical model. It is demonstrated that the larger values of delta(s) reported previously for polycrystalline samples originate from contributions of low-coordinated surface sites. Implications of the present findings f or an improved understanding of the surface electronic structure of ra re-earth metals are briefly discussed.