Intra-atomic Multiplet Coupling Research Articles

Charge Transfer Effects on Fe 2p X-ray Photoemission of RbMn[Fe(CN)6], K3Fe(CN)6, and K4Fe(CN)6

In the studies on the valence transition in RbMn[Fe(CN) 6 ], the Fe valence was determined by observing the binding energy of the primary Fe 2 p photoemission line, while the detailed analysis of the whole Fe 2 p X-ray photoemission spectrum (XPS) has not so far been performed both experimentally and theoretically. In the present study, the Fe 2 p XPS is calculated for [Fe(CN) 6 ] 3- and [Fe(CN) 6 ] 4- cluster models by a configuration-interaction full-multiplet theory. The result shows that the line shape of the Fe 2 p XPS is affected by ligand-to-metal charge transfer (LMCT) and intra-atomic multiplet coupling. It is in clear contrast to the Fe 2 p X-ray photoabsorption spectrum (XAS), where metal-to-ligand charge transfer (MLCT) plays an important role. It is clearly shown that the difference in the ground-state wavefunction between the [Fe(CN) 6 ] 3- and [Fe(CN) 6 ] 4- clusters is reflected in the CT satellite structures and the multiplet structures in the Fe 2 p XPS. From the analysis of the observed...

Theory of resonant X-ray emission spectroscopy in Sc halides

Theoretical calculations of the Sc 2p→3d→2p resonant X-ray emission spectroscopy (RXES) in ScF 3, ScCl 3 and ScBr 3 are performed with a ScX 6 (X = F, Cl and Br) cluster model. Effects of incident photon polarization, intra-atomic multiplet coupling and interatomic hybridization are taken into account. We pay attention to the intensity ratio of the RXES spectra arising from nonbonding states, which has mainly two peaks due to the crystal field splitting. From the change of the spectral intensity in RXES we can find that the highest energy structure of the main peaks in X-ray absorption spectroscopy (XAS) varies from almost pure e g state to the e g and t 2g mixed state according to the strength of multiplet effect and hybridization effect.

ORBITAL ORDERING IN LaMnO3: CLUSTER MODEL CALCULATION OF RESONANT X-RAY SCATTERING AND X-RAY ABSORPTION AT THE MnL2,3 EDGE

We report theoretical results for resonant X-ray scattering (RXS) and linear dichroism (LD) in X-ray absorption spectra at the Mn L 2,3 edge in LaMnO 3, with special attention to the observation of orbital ordering. Calculations were performed on a ( MnO 6)10- cluster with D 4h symmetry, including the effect of intra-atomic multiplet coupling in the Mn ion. Anisotropy effects are also included, through the anisotropic Mn 3d– O 2p hybridization and crystal field parameters for Mn 3d states. The agreement between theory and experiment is good. Moreover, we show that the intensity of the peaks at the L 3 edge are strongly dependent on the Jahn–Teller distortion, while the peaks at the L 2 edge are mostly related to the orbital ordering.

Resonant inelastic x-ray scattering spectra for electrons in solids

conservation are discussed. At the opposite extreme are rare-earth systems (metals and oxides), in which the 4f electrons are almost localized with strong electron correlation. The observations are interpreted based on the effects of intra-atomic multiplet coupling and weak interatomic electron transfer, which are well described with an Anderson impurity model or a cluster model. In this context a narrowing of spectral width in the excitation spectrum, polarization dependence, and the magnetic circular dichroism in ferromagnetic materials are discussed. The authors then consider transition-metal compounds, materials with electron correlation strengths intermediate between semiconductors and rare-earth systems. In these interesting cases there is an interplay of intra-atomic and interatomic electronic interactions that leads to limitations of both the band model and the Anderson impurity model. Finally, other topics in resonant x-ray emission studies of solids are described briefly.

Kβ resonant x-ray emission spectra inMnF2

We report experimental and theoretical results on Mn $K\ensuremath{\beta}$ resonant x-ray emission spectra $(K\ensuremath{\beta}$ RXES) at the pre-edge region of K-edge x-ray absorption spectroscopy in a powdered ${\mathrm{MnF}}_{2}$ sample. The experimental results are studied theoretically in terms of coherent second-order optical process, using a ${\mathrm{MnF}}_{6}^{\ensuremath{-}4}$ cluster model with the effects of intra-atomic multiplet coupling and interatomic hybridization in the space of three configurations and taking into account both the Mn $1s\ensuremath{-}3d$ quadrupole excitation and the Mn $1s\ensuremath{-}4p$ dipole excitation. The agreement between theory and experiment is good. Moreover, we show that if the sample is a single crystal the resonant x-ray emission spectroscopy caused by the quadrupole excitation has a strong sensitivity to the angle of the incident photon.

1s2presonant inelastic x-ray scattering inα−Fe2O3

We report experimental and theoretical results on the Fe K edge x-ray absorption spectrum and $1s2p$ resonant inelastic x-ray scattering (RIXS) spectra in $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}.$ The results are interpreted using an ${\mathrm{FeO}}_{6}^{9\ensuremath{-}}$ cluster model with intra-atomic multiplet coupling and interatomic covalency hybridization. The $1s2p$ RIXS is treated as a coherent second-order optical process. It is shown that the double-peak structure in the pre-edge region of Fe K absorption spectrum is due to the cubic crystal-field splitting, and that the intensity of the ${e}_{g} {(t}_{2g})$ component in the $1s2p$ resonant inelastic spectrum is enhanced by tuning the incident photon energy to the ${e}_{g} {(t}_{2g})$ component in the absorption spectrum.

Interplay between intra-atomic multiplet coupling and interatomic hybridization in core-level spectroscopy

Abstract Interplay between atomic multiplet and solid-state hybridization often plays an important role in the core-level spectroscopy of f and d electron systems. Here a short review is given of theoretical analyses of core-level spectra in rare-earth oxide systems, where the effects of the intra-atomic multiplet coupling and interatomic hybridization are taken into account with the impurity Anderson model. Some examples of theoretical calculations are shown for 3d X-ray photoemission spectra (XPS) and 4d X-ray absorption spectra (XAS) of CeO 2 and for 4d XPS of Pr 2 O 3 . For 4d XPS of heavy rare-earth systems, the effect of term-dependent lifetime of the 4d core hole is shown to be essential in explaining the spectral shape. A recent analysis of resonant X-ray emission spectra for CeO 2 is also given.

Theory of X-Ray Absorption and Resonant X-Ray Emission Spectra

Resonant X-ray emission spectrum (RXES) has recently been a subject of remarkable progress. Theoretically, RXES is formulated as a coherent second order optical process, where the X-ray emission follows the X-ray absorption (XAS) of a core electron. In this paper I discuss from theoretical viewpoint XAS and RXES in f and d electron systems, which are calculated with an impurity Anderson model. Effects of intra-atomic multiplet coupling and interatomic hybridization are taken into account. RXES is calculated for some rare earth compounds and transition metal compounds as a function of the emitted photon energy ω, and it is shown that the RXES gives us information on the electronic excitations (multiplet states and charge transfer states) in the ground state configuration. When we regard RXES as a function of the incident photon energy it with fixed ω, the RXES gives us information on the core electron excited states (with more information than XAS). These results are also compared with available experimental data.

Theoretical studies on core-level spectra of solids

A review is presented of theoretical studies on core-level spectroscopy in solids. In core level spectra, the dynamical response of outer electrons to the core hole is reflected through the screening of core hole potential. Impurity Anderson model (IAM) or cluster model is successfuly applied to the analysis of X-ray photoemission spectra (XPS), X-ray absorption spectra (XAS) and X-ray emission spectra (XES) in f and d electron systems, where the f and d electron states are hybridized with the other valence or conduction electron states. The effect of a core-hole potential plays an important role in these spectra, as well as the hybridization and intra-atomic multiplet coupling effects. Some typical examples for core-level spectra in rare-earth compounds and transition-metal compounds are shown with some discussions.

Theory of core-level spectroscopy in actinide systems

We analyze the actinide 4f core X-ray photoemission spectra for actinide dioxide series, ThO 2, UO 2−BkO 2, using the impurity Anderson model. Systematic variations of physical parameters, such as the charge transfer energy and the covalency hybridization strength, are investigated with the change of the actinide elements. We also calculate uranium 5d core X-ray absorption spectra (5d-XAS) of UO 2 and other U compounds taking into account the effect of multiplet coupling. We discuss an important role of the interplay between the intra-atomic multiplet coupling and the inter-atomic hybridization on the 5d-XAS.

Theory of core level X-ray photoemission and photoabsorption in Ti compounds

We analyze the Ti2p X-ray photoemission spectroscopy (XPS) and photoabsorption spectroscopy (XAS) spectra in formally tetravalent Ti compounds such as TiO 2, SrTiO 3 and BaTiO 3, by means of a TiO 6 cluster model, paying particular attention to the interplay between the Ti3dO2p hybridization and the intra-atomic multiplet coupling. We also show that the satellite peaks observed in the Ti2p XPS and XAS spectra can be understood as charge transfer satellites, although they have until now been ascribed to the exciton satellite which originates from the excitation from the O2p to O3s states.

Many Body Effects in the X-ray Absorption Edge of Rare-Earth Systems

A review is presented of many body effects originating from intraatomic multiplet coupling and interatomic hybridization in the X-ray absorption spectra (XAS) of rare-earth systems. With CeO2 as an example, the Ce N4,5, M4,5 and L3 XAS are theoretically analyzed with the impurity Anderson model, and the importance of the interplay between the multiplet coupling and the hybridization is shown for N4,5 and M4,5 XAS. Then we calculate a pre-edge structure of L3 XAS in Dy compounds, and discuss an elimination of the lifetime broadening in the L3 XAS, which has recently been attained experimentally by observing the excitation spectrum of L3-M5 X-ray emission.

Interatomic and Intra-Atomic Configuration Interactions in Core-Level X-Ray Photoemission Spectra of Late Transition-Metal Compounds

We theoretically investigate X-ray photoemission spectra (XPS) from transition metal 2 p and 3 s core levels in late transition metal compounds in terms of an MX 6 cluster model (M=Mn∼Ni; X=halogen or oxygen), paying particular attention to the interplay between the intra-atomic multiplet coupling and covalency mixing effects. In the analysis of 3 s -XPS, we also take into account the intra-atomic configuration interaction between 3 s 1 3 p 6 3 d n and 3 s 2 3 p 4 3 d n +1 electron configurations. The systematic change of 2 p -XPS and 3 s -XPS on going from Ni to Mn compounds or from fluorides to bromides is mainly ascribed to that of the charge transfer energy from X to M ion. In the analysis, we show that the final state effects are very important in the 3 s -XPS as well as in the 2 p -XPS.

Charge transfer satellites and multiplet splitting in X-ray photoemission spectra of late transition metal halides

Core-level X-ray photoemission spectra (XPS) are calculated for Ni and Co dihalides with an MX 6 cluster model (M = Ni, Co; X = F, Cl, Br), where intra-atomic multiplet coupling as well as covalency mixing is taken into account. The effects of the intra-atomic configuration interaction between (3s) 1(3p) 6(3d) n and (3s) 2(3p) 4(3d) n+1 , which is known to be important in the 3s XPS, are treated phenomenologically. The overall spectral shape of the Ni (Co) 2p XPS can be explained by a charge transfer mechanism, and the difference in the line shape between the Ni (Co) 2p 3 2 and 2p 1 2 XPS spectra is shown to originate from the multiplet splitting of their charge transfer satellites. However, the Ni (Co) 3s XPS are so complex that it is difficult to discriminate between exchange split pairs and their charge transfer satellites. As for Co dihalides, the spectral splitting of the 3s XPS mostly represents the 3s-3d exchange splitting of the (3s) 1(3d) 8 configuration. However, in Ni dihalides the first satellite peak is mainly due to charge transfer.

Praseodymium 3d- and 4d-core photoemission spectra of Pr2O3.

Experimental data and theoretical calculations are shown for Pr 3d and 4d x-ray photoemission spectra (XPS) of ${\mathrm{Pr}}_{2}$${\mathrm{O}}_{3}$. The observed spectral structures are well explained by the theoretical results that are obtained with the impurity Anderson model by combining intra-atomic multiplet coupling with solid-state hybridization between the Pr 4f and O 2p states. For 3d XPS the main spectral structures are caused by the hybridization effect, while for 4d XPS the interplay between the multiplet coupling and the hybridization is essential.

Multiplet Splitting in Ni 2pX-Ray Photoemission Spectra of Ni Dihalides

A cluster model approach is applied to the analysis of the Ni 2 p core-level X-ray photoemission spectra (XPS) in Ni dihalides, where the intraatomic multiplet coupling is fully taken into account. The difference in the line shape between the 2 p 3/2 and 2 p 1/2 spectra is shown to originate from the multiplet splitting of their charge transfer satellites.

Core-Level Spectroscopy in High-Tc Superconductors

A short review is presented on the spectroscopic study of X-ray photoemission (XPS), X-ray absorption (XAS) and X-ray emission (XES) associated with the Cu 2p and O 1s core-levels in high- Tc systems and related materials. Experimental data are analyzed using the single-site impurity Anderson model (and its extension) with Cu 3d orbitals and O 2p valence bands specified by irreducible representations of the D4h symmetry around the Cu atom. By analyzing Cu 2p-XPS, we can get information on the hybridization strength between Cu 3d and O 2p states and the charge transfer energy. In determining the spectral shape of the XPS satellite, it is shown that the interplay between the intraatomic multiplet coupling and the solid-state hybridization plays an essential role. The Cu 2p-XAS, especially its polarization dependence, gives the most direct information on the site and the symmetry of doped holes. Finally, we show the Cu 2p-XES can also be interpreted with the impurity Anderson model in a manner consistent with XPS and XAS.