Eur. Phys. J. Special Topics 169, 199–205 (2009) c  EDP Sciences, Springer-Verlag 2009 DOI: 10.1140/epjst/e2009-00993-8 T HE EUROPEAN P HYSICAL JOURNAL SPECIAL TOPICS Regular Article Crystal field and low energy excitations measured by high resolution RIXS at the L 3 edge of Cu, Ni and Mn G. Ghiringhelli 1, a , A. Piazzalunga 1 , X. Wang 2 , A. Bendounan 3 , H. Berger 2 , F. Bottegoni 1 , N. Christensen 3 , C. Dallera 1 , M. Grioni 2 , J.-C. Grivel 4 , M. Moretti Sala 1 , L. Patthey 5 , J. Schlappa 5 , T. Schmitt 5 , V. Strocov 5 , and L. Braicovich 1 1 CNR-INFM Coherentia and Soft, Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, 20133 Milano, Italy 2 Institut de Physique des Nanostructures, ´ Ecole Polytechnique F´ ed´ erale (EPFL), 1015 Lausanne, Switzerland 3 Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, 5232 Villigen PSI, Switzerland 4 Materials Research Department, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, 4000 Roskilde, Denmark 5 Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland Abstract. Resonant inelastic x-ray scattering in the soft x-ray regime has been profiting much from technical advances that have lowered considerably the instru- mental linewidth. At the ADRESS beam line of the Swiss Light Source the SAXES spectrometer can be used to measure RIXS spectra at the L edges of the 3d transition metals with unprecedented energy resolution, of the order of 100 meV for Mn, Ni and Cu. We present here some preliminary spectra on CuO, malachite, NiO, NiCl 2, MnO and LaMnO3. The dd excitations are very well resolved allowing accurate experimental evaluation of 3d state energy splitting. The low energy scale becomes accessible opening the way to the study of collective excitations in strongly correlated electron systems, like magnons and orbitons. 1 Introduction Since the last decade resonant inelastic x-ray scattering (RIXS) has been considered as one of the most innovative and promising among the new spectroscopic techniques made possible by third generation synchrotron radiation sources. RIXS is intrinsically chemical selective owing to the resonant excitation that involves a core hole creation, but it does not suffer from large intrinsic broadening coming from the core hole lifetime because its final state, in most of the cases, presents only valence excitations. As it does not involve electron beams it is highly bulk sensitive and magnetic or electric fields are of no obstacle to the measurements. RIXS can be measured at diverse photon energy ranges [1, 2], from VUV for M 2,3 edges of 3d transition metals (3dTM) [3,4] and N 4,5 edges of rare earths (RE) [5], to soft x rays (L 2,3 edges of 3dTM [6], K edge of oxygen [7] and M 4,5 of RE [8]), to hard x rays (K edge of 3dTM [9,10] and L 2,3 of RE). Restricting ourselves to the case of 3dTMs, M and L edge are in principle very similar as np ↔ 3d transitions are involved in both cases, giving a direct access to the 3d valence electron configurations and thus to crystal field excitations. They differ in the strength of the absorption resonance and of the core-hole spin-orbit interaction: both are stronger for 2p states, leading to a e-mail: giacomo.ghiringhelli@fisi.polimi.it