DETERMINATION OF THE ELECTRONIC-STRUCTURE IN THE STRONGLY CORRELATED 1-D ELECTRON-SYSTEMS - X-RAY PHOTOELECTRON AND AUGER-SPECTROSCOPY OF HALOGEN-BRIDGED NICKEL-COMPLEXES

The electronic structure of the I-D Ni complexes, [Ni(chxn)(2)X]X-2 (X =Br, Cl) is studied together with the discrete Ni complexes, [NiX2([14 ]aneN(4))]ClO4 (X=Br, Ci), using X-ray photoelectron spectroscopy (XPS ) and Auger electron spectroscopy (AES). An analysis using a simple X- Ni-X trimer model on the Ni 2p XP spectra yields quantitative estimate s for the charge transfer (CT? energy Delta and the transfer energy T. An analysis on the Ni LW Auger spectra indicates that the average on- site Coulomb energy U in these Ni complexes is about 5 eV. The obtaine d results demonstrate that the I-D Ni complexes are CT insulators.