INNER-SHELL EXCITATIONS OF THE CORRELATED INSULATOR MNO(100)

One- and two-electron excitations of core electrons into unoccupied st ates of the correlated 3d transition metal monoxide MnO(100) were inve stigated by core electron energy loss spectroscopy (CEELS) and appeara nce potential spectroscopy (APS: SXAPS and TCAPS) at the metal 2p and the ligand Is thresholds. Unlike in the spectra of NiO, the number of the structures in the APS spectra at the oxygen Is threshold exhibits no direct influence of the electron correlation, because all dominant peaks can be explained by one-electron transitions of an oxygen core e lectron into unoccupied manganese 3d, 4s and 4p states. Integrated CEE LS spectra and APS spectra at the oxygen is threshold show good agreem ent. But in the APS spectra at the manganese 2p threshold we find two- electron excitations which are absent in one-electron excitation spect ra. In this case a value for the electron correlation energy U-dd can be estimated. (C) 1998 Elsevier Science B.V. All rights reserved.