title: Nonresonant inelastic x-ray scattering involving excitonic excitations: the examples of NiO and CoO.
abstract: In a recent publication Larson et al. reported remarkably clear d-d excitations for NiO and CoO with x-ray scattering. Here we present an accurate quantitative description based on a local many body approach, beyond local density approximation + Hubbard U approximations. The magnitude of q[over -->] determines which of the allowed multipoles contributes most to the spectra. The direction of q[over -->] with respect to the crystal can be used as an equivalent to polarization similar to electron energy loss spectroscopy, allowing for a determination of the local symmetry of the initial and final states. This method is more generally applicable and could be a powerful tool for the study of local distortions and symmetries in transition metal and rare earth compounds.
authors.affiliation: II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany.
authors.forename: M W
authors.initials: MW
authors.lastname: Haverkort
authors.forename: A
authors.initials: A
authors.lastname: Tanaka
authors.forename: L H
authors.initials: LH
authors.lastname: Tjeng
authors.forename: G A
authors.initials: GA
authors.lastname: Sawatzky