VALENCE STATE OF LOW-DIMENSIONAL THULIUM STRUCTURES GROWN ON MOLYBDENUM (110)

Valence band photoemission spectra of well-defined structures of the r are earth Tm deposited onto a Mo(110) surface have been measured using synchrotron radiation. The results correlate with the overlayer struc ture; mixed valence is observed at low coverages, in areas of island f ormation and beyond one monolayer. The presence of divalent features i s associated with low coordinated sites, which provide insufficient tr ansfer of energy to promote a LAMBDA1+ electron into the valence 5d6s states. This is consistent with theoretical predictions.