STUDY OF THE VALENCY OF RARE-EARTH ATOMS IN THE MISFIT-LAYER COMPOUNDS (RS)1-NBS2 (R = LA, CE, SM) USING RESONANT PHOTOEMISSION AND X-RAY-ABSORPTION SPECTRA(DELTA)

The photoelectron spectrum of (CeS)1.16NbS2 shows a strong resonance e nhancement at a photon energy of 120 eV for states with a binding ener gy of 2.4 eV. The resonance is due to Ce 4d(10)4f1-->4d(9)4f2 transiti ons, and is evidence that the Ce atoms in this compound have the valen cy Ce3+ (4f1). The 3d x-ray-absorption spectrum of (LaS)1.14NbS2, (CeS )1.16NbS2, and (SmS)1.19NbS2 exhibit a multiplet structure which is ch aracteristic for La3+ (4f0), Ce3+ (4f1), and Sm3+ (4f5). We conclude t hat in the misfit-layer compounds (RS)1+deltaNbS2 (R = La,Ce,Sm) the r are-earth atoms are trivalent.