THERMAL EFFECTS ON PHOTOEMISSION SPECTRA OF LANTHANIDE METALS

We report on a systematic study of thermal effects on 4f photoemission (PE) spectra from close-packed surfaces of the monocrystalline lantha nide metals Tb, Yb, and Lu, in particular on broadening of surface and bulk lines. Such effects can be best studied for Yb(111) and Lu(0001) , which display the hitherto best resolved surface-shifted PE componen ts. In all studied cases, the PE lines from the topmost surface layer exhibit much stronger thermal broadening than those from the bulk, wit h reduced surface Debye temperatures. The broadening is found to be la rger for the trivalent metals Tb and Lu as compared to divalent Yb met al.