High-resolution electron energy loss studies of some transition metal oxides

High resolution electron energy loss spectra have been measured for a variety of first-row transition metal oxides for loss energies of up to 5 eV. The features observed are qualitatively consistent with the electronic properties of these materials (i.e., a highly damped plasmon for metals, and local d-d excitations for insulators), with the notable exception of CuO. Quantitatively, however, the intensities of the d-d transitions are an order of magnitude greater than expected from optical dipole strengths, and the authors evaluate possible explanations for this.