SEMINAR      Tuesday, 28th October 2003 - h. 14:30  Aula A1     P. Ferriani INFM, National Research Center on Nanostructures and Biosystems at Surfaces (S3), Unita’ di Ricerca di Modena and Dipartimento di Fisica, Univ. di Modena e Reggio Emilia        ANGLE RESOLVED RESONANT INELASTIC X-RAY SCATTERING: INTENSITY AND DICHROISM FROM 3d TRANSITION METALS IN SPECIAL GEOMETRIES           Abstract Resonant inelastic x-ray scattering is an element selective experimental technique that emerged as an extremely powerful tool for investigating electronic and magnetic ground state properties of strongly correlated electron systems. We are particularly interested in the process involving the L3 threshold in the absorption and the 3s _ 2p transition in the emission. A theoretical study of the cross section and of its dependence on the geometrical set-up of the experiment and on the incident photon polarization, that is of the outmost importance for interpreting the experimental results, is presented here. With the choice of the perpendicular geometry for the incoming photon and by scanning the angular dependence of the outcoming photon, it is possible to obtain important information concerning the ground state, such as the multipole moments of the charge and magnetic densities, even of high order. We provide a detailed description about the angular dependence of the dichroism and unpolarized signals. The unusual case where the emission direction is out of the plane containing the direction of the incident photon and the sample magnetization is also analysed. In this case an asymmetry for emission with respect to this plane, which is linked to the magnetic structure of the system, is observed. This new result supplies a test for the applicability of the so-called fast collision approximation, necessary in order to extract the multipole moments of the system by measuring the angular dependence of the magnetic circular dichroism in the resonant scattering process. Numerical calculations on 3d transition metal systems, based on multiplet atomic model with the inclusion of the appropriate crystal and magnetic field, are given.