Dipole and quadrupole contributions to polarized Cu<b><i>K</i></b>x-ray absorption near-edge structure spectra of CuO

Bocharov, S.; Kirchner, Th.; Dräger, G.; Šipr, O.; Šimůneḱ, A.

doi:10.1103/physrevb.63.045104

Cited by 39 publications

(53 citation statements)

References 35 publications

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“…We follow the notation of refs. 38,39 and label the configuration of the crystal with respect to the incident beam by the three angles (θ, φ, ψ). These angles correspond to the three rotation angles of the goniometer.…”

Section: Copper Oxidementioning

confidence: 99%

K-edge x-ray absorption spectra in transition-metal oxides beyond the single-particle approximation: Shake-up many-body effects

et al. 2012

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The near edge structure (XANES) in K-edge X-ray absorption spectroscopy (XAS) is a widely used tool for studying electronic and local structure in materials. The precise interpretation of these spectra with the help of calculations is hence of prime importance, especially for the study of correlated materials which have a complicated electronic structure per se. The single particle approach, for example, has generally limited itself to the dominant dipolar cross-section. It has long been known however that effects beyond this approach should be taken into account, both due to the inadequacy of such calculations when compared to experiment and the presence of shake-up many-body satellites in core-level photoemission spectra of correlated materials. This effect should manifest itself in XANES spectra and the question is firstly how to account for it theoretically and secondly how to verify it experimentally. By using state-of-the-art first principles electronic structure calculations and 1s photoemission measurements we demonstrate that shake-up manybody effects are present in K-edge XAS dipolar spectra of NiO, CoO and CuO at all energy scales. We show that shake-up effects can be included in K-edge XAS spectra in a simple way by convoluting the single-particle first-principles calculations including core-hole effects with the 1s photoemission spectra. We thus describe all features appearing in the XAS dipolar cross-section of NiO and CoO and obtain a dramatic improvement with respect to the single-particle calculation in CuO. These materials being prototype correlated magnetic oxides, our work points to the presence of shake-up effects in K-edge XANES of most correlated transition metal compounds and shows how to account for them, paving the way to a precise understanding of their electronic structure.

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Section: Copper Oxidementioning

confidence: 99%

K-edge x-ray absorption spectra in transition-metal oxides beyond the single-particle approximation: Shake-up many-body effects

et al. 2012

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“…10 This statement is true much more for the TFY XANES deduced from our spectra in Ref. 9 and for those in Refs.…”

mentioning

confidence: 58%

“…10 we can assign the OSD peak c predominantly to 1s → 3d electric-quadrupole transitions. All other OSD structures at higher excitation energies should be 1s → 4p electric-dipole excitations.…”

mentioning

confidence: 99%

Numerical method for inverting1s2presonant inelastic x-ray scattering spectra: Interpretation of hidden electronic excitations in CuO

Dräger

Machek

2009

Phys. Rev. B

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Direct inversion of resonant inelastic x-ray scattering spectra ͑RIXSS͒ has been carried out using a numerical method for solving first-kind Fredholm integral equations. Hereby, the oscillator strength distribution ͑OSD͒, which is proportional to the empty density of states at the absorption edge, has been obtained from the experimental Cu 1s2p RIXSS of CuO. In particular, the inversion of RIXSS measured at incident energies below the K level threshold provides OSD having a better resolution than it can be achieved with one of the customary x-ray absorption near-edge structure spectroscopies. This can be explained by the virtual character of the intermediate states at low energy excitation. By means of the presented method a so-called "hidden electronic excitation" of CuO has been identified as a very weak core excitation. Furthermore, numerical interpretation of polarized spectra has revealed the p y -like character of the excited states in a suitable local reference frame. The obtained results are promising for further applications of the method, preferred in the field of strongly correlated materials. Core excitations into unoccupied levels are sometimes so weak that they apparently do not leave behind visible features in the x-ray absorption near-edge structure ͑XANES͒. However, they can become detectable in the resonant inelastic x-ray scattering spectra ͑RIXSS͒ and in this context the term "hidden electronic excitations" is used.1 The great sensitivity by resonance amplification and the higher energetic resolution as compared with conventional XANES spectroscopies make RIXS spectroscopy a powerful method for investigating unoccupied states in condensed matter, frequently in strongly correlated materials. Among them, divalent CuO with its CuO 4 plaquettes similar to those in the high T c compounds is a good model system toward the understanding of the electronic structure of these materials.Recently, some of the studies on CuO have shown the advantages of RIXS compared to other XANES spectroscopies, but they have also left open questions. In Ref. 2 the existence of a pronounced structure in the Cu 1s2p emission of CuO was discovered for incident energies between 8980 and 8984 eV but without finding a visible counterpart in the corresponding total fluorescence yield ͑TFY͒ XANES. Unfortunately, as the experimental data were obtained from a powder sample, the authors were not able to determine the character and symmetry of the "hidden" excited state. Polarized RIXSS on CuO were measured later by Döring et al. derived oscillator strength distributions ͑OSDs͒ analytically from the experimental 1s2p RIXSS and obtained XANESlike spectra in which the lifetime-broadening ⌫ 1s due to the 1s core hole was suppressed. They compared the spectra with conventional and high-resolution fluorescent excitation ͑HRFE͒ XANES and found that the method revealed weak details in the spectra in the same quality as HRFE. An alternative method to identify even weak spectra structures is based on the interpretation of experimental spec...

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“…[61][62][63][64][65][66][67] In this relaxed state, the core hole is stabilized through additional screening due to partial charge transfer from the ligand orbital L to the half-filled metal orbital 3dx 2 -y 2 , a process generally known as shakedown. This transition denoted 1s  4p+shakedown is a sensitive fingerprint for any modification in the covalency of the metal-ligand bond.…”

Section: Spectroscopic Characterizations Of Cumentioning

confidence: 99%

Elucidating the Ultrafast Dynamics of Photoinduced Charge Separation in Metalloporphyrin-Fullerene Dyads Across the Electromagnetic Spectrum

et al. 2016

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Metalloporphyrins are prominent building blocks in the synthetic toolbox of advanced photodriven molecular devices. When the central ion is paramagnetic, the relaxation pathways within the manifold of excited states are highly intricate so that unravelling the intramolecular energy and electron transfer processes is usually a very complex task. This fact is critically hampering the development of applications based on the enhanced coupling offered by the electronic exchange interaction. In this work, the dynamics of charge separation in a copper porphyrin-fullerene are studied with several complementary spectroscopic tools across the electromagnetic spectrum (from near infra-red to X-ray wavelengths), each of them providing specific diagnostics. Correlating the various rates clearly demonstrates that the lifetime of the photoinduced charge-separated state exceeds by about 10 fold that of the isolated photoexcited Cu II porphyrin. As revealed by the spectral modifications in the XANES region, this stabilization is accompanied by a transient change in covalency around the Cu II center, which is induced by an enhanced interaction with the C 60 moiety. This experimental finding is further confirmed by state-of-the art calculations using DFT and TD-DFT including dispersion effects that explain the electrostatic and structural origins of this interaction, as the Cu II P cation becomes ruffled and approaches closer to the fullerene in the charge-separated state. From a methodological point of view, these results exemplify the potential of multielectron excitation features in transient X-ray spectra as future diagnostics of sub-femtosecond electronic dynamics. From a practical point of view, this work is paving the way for elucidating out-ofequilibrium electron transfer events coupled to magnetic interaction processes on their intrinsic time-scales.

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Dipole and quadrupole contributions to polarized CuKx-ray absorption near-edge structure spectra of CuO

Cited by 39 publications

References 35 publications

K-edge x-ray absorption spectra in transition-metal oxides beyond the single-particle approximation: Shake-up many-body effects

K-edge x-ray absorption spectra in transition-metal oxides beyond the single-particle approximation: Shake-up many-body effects

Numerical method for inverting1s2presonant inelastic x-ray scattering spectra: Interpretation of hidden electronic excitations in CuO

Elucidating the Ultrafast Dynamics of Photoinduced Charge Separation in Metalloporphyrin-Fullerene Dyads Across the Electromagnetic Spectrum

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