title: Molecular Orbital Simulations of Metal 1s2p Resonant Inelastic X-ray Scattering.
abstract: For first-row transition metals, high-resolution 3d electronic structure information can be obtained using resonant inelastic X-ray scattering (RIXS). In the hard X-ray region, a K pre-edge (1s→3d) excitation can be followed by monitoring the dipole-allowed Kα (2p→1s) or Kβ (3p→1s) emission, processes labeled 1s2p or 1s3p RIXS. Here the restricted active space (RAS) approach, which is a molecular orbital method, is used for the first time to study hard X-ray RIXS processes. This is achieved by including the two sets of core orbitals in different partitions of the active space. Transition intensities are calculated using both first- and second-order expansions of the wave vector, including, but not limited to, electric dipoles and quadrupoles. The accuracy of the approach is tested for 1s2p RIXS of iron hexacyanides [Fe(CN)6](n-) in ferrous and ferric oxidation states. RAS simulations accurately describe the multiplet structures and the role of 2p and 3d spin-orbit coupling on energies and selection rules. Compared to experiment, relative energies of the two [Fe(CN)6](3-) resonances deviate by 0.2 eV in both incident energy and energy transfer directions, and multiplet splittings in [Fe(CN)6](4-) are reproduced within 0.1 eV. These values are similar to what can be expected for valence excitations. The development opens the modeling of hard X-ray scattering processes for both solution catalysts and enzymatic systems.
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University , Box 538, SE-751 21 Uppsala, Sweden.
authors.forename: Meiyuan
authors.initials: M
authors.lastname: Guo
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University , Box 538, SE-751 21 Uppsala, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Källman
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University , Box 538, SE-751 21 Uppsala, Sweden.
authors.forename: Lasse Kragh
authors.initials: LK
authors.lastname: Sørensen
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University , Box 538, SE-751 21 Uppsala, Sweden.
authors.forename: Mickaël G
authors.initials: MG
authors.lastname: Delcey
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University , Box 538, SE-751 21 Uppsala, Sweden.
authors.forename: Rahul V
authors.initials: RV
authors.lastname: Pinjari
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University , Box 538, SE-751 21 Uppsala, Sweden.
authors.forename: Marcus
authors.initials: M
authors.lastname: Lundberg
mesh_terms: D007501:Iron / Q000737:chemistry*; D011789:Quantum Theory; D012542:Scattering, Radiation; D014965:X-Rays
chemical_list: D007501:Iron