L-Edge Absorption and Dichroism in Low Symmetry $3d^0$ Compounds

Abstract

Inorganic compounds containing light transition metal ions in a formal ($3d^0$) electronic configuration often have a complex atomic structure and several polymorphs may co-exist, especially in nanomaterials. X-ray absorption spectra at the metal L-edge probes the symmetry, electronic state and bonding of the transition metal ion. In low symmetry crystals, linear dichroism is common and reflects a complicated ligand field. We show that the metal $L_{2,3}$-edge spectra, which are dominated by strong particle-hole multiplet coupling, are well described with multichannel multiple scattering theory. The ligand field and band effects are included ab initio by the anisotropic scattering of the excited electron, whereby complex dichroism can be accounted for. Titanite nanostructures and calcium carbonate are taken as examples.