Multiplet effects in X-ray spectroscopy

Abstract

This review gives an overview of the presence of multiplet effects in X-ray spectroscopy, with an emphasis on X-ray absorption studies on 3d transition metal ions in inorganic oxides and coordination compounds. The first part of the review discusses the basics of multiplet theory and respectively, atomic multiplets, crystal field effects and charge transfer effects are explained. The consequences of 3d-spin-orbit coupling and of 3d systems in symmetries lower than cubic are discussed. The second part of the paper gives a short overview of all X-ray spectroscopies, where the focus is on the multiplet aspects of those spectroscopies and on the various configurations that play a role in combined spectroscopies such as resonant photoemission, resonant X-ray emission and coincidence spectroscopy. The review is concluded with a section that gives an overview of the use of multiplet theory for 3d coordination compounds. Some new developments are sketched, such as the determination of differential orbital covalence and the inclusion of-(back)bonding.

Direct Contact versus Solvent-Shared Ion Pairs in NiCl2 Electrolytes Monitored by Multiplet Effects at Ni(II) L Edge X-ray Absorption

“…The satellite peak is known to be due to the Ligand Metal Charge Transfer (LMCT) from Cl− to Ni 2+ , 15 which is possible due to the close proximity of Ni and Cl in the solid. An overview spectrum for NiCl 2 aqueous solution is shown for comparison.…”

“…15 All spectra shown in this work have been broadened by a Lorenzian of 0.2 eV and 0.3 eV for L 3 and L 2 edges, respectively, and a Gaussian of 0.25 eV in order to account for lifetime broadening and the experimental resolution, respectively.…”

“…The spectra have 4 been analyzed by the means of a charge transfer multiplet simulation. [15][16][17] The multiplet approach has been extensively used in the analysis of L-edge spectra of transition metals, where it is established as a method for probing the metal ligand charge transfer. [18][19][20][21] …”

X-ray photoelectron spectroscopy study of electron and spatial structure of mono- and binuclear Ni(II) carboxylate complexes with nitrogen-containing ligands

“…[15]. Most important among them is the multiplet splitting, which gives the grounds for using the isolated-ion approximation to calculate the structure of the XPS spectra of the compounds.…”

“…Basics of the assigning of 3s-, 3p-and 2p-XPS spectra of transition metals on the basis of the atomic multiplets theory are systematically laid out, for example, in [15]; they are outlined below.…”