On the origin of dips in total fluorescence yield X-ray absorption spectra: Partial and inverse partial fluorescence yield at the L-edge of cobalt aqueous solution

Soldatov, Mikhail A.; Lange, Kathrin M.; Götz, Malte; Engel, Nicholas; Golnak, Ronny; Kothe, Alexander; Aziz, Emad F.

doi:10.1016/j.cplett.2012.07.067

Cited by 23 publications

(36 citation statements)

References 21 publications

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“…It was claimed that the transfer would be the more efficient and correspondingly the dip would be the deeper, the stronger the orbital overlap between the metal d-orbitals and the solvent orbitals would be. While resonant photoelectron and fluorescence yield spectroscopy of aqueous Co 2+ ions have been used to allegedly confirm the origin of "dark channel fluorescence" (27,28) two investigations based on calculated spectra of free metal ions (29) and measured spectra of a solid compound (30) recently proposed alternative explanations for the observed dips.…”

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confidence: 99%

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Dissecting Local Atomic and Intermolecular Interactions of Transition-Metal Ions in Solution with Selective X-ray Spectroscopy

Wernet

Kunnus

Schreck

et al. 2012

J. Phys. Chem. Lett.

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Determining covalent and charge-transfer contributions to bonding in solution has remained an experimental challenge. Here the quenching of fluorescence-decay channels as expressed in dips in the L-edge x-ray spectra of solvated 3d transition-metal ions and complexes was reported as a probe. With a full set of experimental and theoretical ab initio L-edge x-ray spectra of aqueous Cr 3+ including resonant inelastic x-ray scattering we address covalency and charge-transfer for this prototypical transition-metal ion in solution. We dissect local atomic effects from intermolecular interactions and quantify x-ray optical effects. We find no evidence for the asserted ultrafast charge-transfer to the solvent and show that the dips are readily explained by xray optical effects and local atomic state dependence of the fluorescence yield. Instead we find, besides ionic interactions, a covalent contribution to the bonding in the aqueous complex of ligand to metal charge transfer character. 3 TOC Graphic:KEYWORDS Charge transfer to solvent, dark channel fluorescence yield, inverse partial fluorescence yield, total fluorescence yield, resonant inelastic x-ray scattering, transition metal ion, aqueous solution. 4The transfer of charge from a solvated ion or molecular complex to the surrounding solvent is an elementary step in numerous reactions in nature and in technological processes. Understanding charge transfer to solvent effects in molecular systems is thus of primary importance and x-ray spectroscopy with its specificity to elemental and chemical sites promises to add a new suite of powerful tools for their investigation (1). Specifically, time-resolved x-ray spectroscopy (2-11) appears to be the most direct way of probing charge transfer initiated by a pump pulse and probed as a function of time by scanning the delay of a short x-ray probe pulse. However, such effects can proceed on the few-femtosecond time scale and it is currently very challenging to achieve a corresponding time-resolution in pump-probe x-ray spectroscopy experiments.Therefore, it has been attempted to make use of the core-hole lifetime of a few femtoseconds to study ultrafast charge transfer processes for various systems such as for adsorbates on surfaces (12-18), ice (19) and aqueous solutions (20). Using resonant soft x-ray spectroscopy a coreelectron is excited into an unoccupied state of the system and the probability for it to transfer to the surroundings during the few-femtosecond core-hole lifetime will influence the core-hole decay channels. The Auger decay signal is thus the stronger, the higher the probability for its transfer to the surrounding medium during the core-hole lifetime is (15,17,18).As core-excited states can decay via Auger-electron ejection or fluorescence, the question arises whether such ultrafast electron-transfer processes are observable in the fluorescence decay channel as well. This relates to the more general questions as to whether and how bonding and charge-transfer processes can be revealed by with x-ray sp...

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“…from the large number of states of the Cr 3+ 2p 5 3d 4 configuration. This is of utmost importance as it shows that one cannot infer from a variation of the fluorescence yield a delocalization of the excited electron or even on orbital mixing or hybridization as recently insinuated (27,28,40,41). …”

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confidence: 99%

Dissecting Local Atomic and Intermolecular Interactions of Transition-Metal Ions in Solution with Selective X-ray Spectroscopy

Wernet

Kunnus

Schreck

et al. 2012

J. Phys. Chem. Lett.

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“…For comparison the spectrum of aqueous CoCl 2 is shown. 24 Upon increasing deposition time an increase in the signal of the Coedge is observed. The spectral features after 345 s deposition time show the rather featureless characteristics of a Co metal film and differ accordingly to the more complex spectral fingerprint of the of the aqueous sample.…”

Section: Proof Of Principle Measurementsmentioning

confidence: 92%

Electrochemical flowcell for in-situ investigations by soft x-ray absorption and emission spectroscopy

Schwanke

Golnak

Xiao

et al. 2014

Review of Scientific Instruments

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A new liquid flow-cell designed for electronic structure investigations at the liquid-solid interface by soft X-ray absorption and emission spectroscopy is presented. A thin membrane serves simultaneously as a substrate for the working electrode and solid state samples as well as for separating the liquid from the surrounding vacuum conditions. In combination with counter and reference electrodes this approach allows in-situ studies of electrochemical deposition processes and catalytic reactions at the liquid-solid interface in combination with potentiostatic measurements. As model system in-situ monitoring of the deposition process of Co metal from a 10 mM CoCl2 aqueous solution by X-ray absorption and emission spectroscopy is presented.

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“…27,28 The incident photon energy was tuned to the Fe L 2,3 edge, while only the Fe 3d->2p transition was selected for the detection of the emitted photon in both XAS (PFY) and RIXS measurements. The first diffraction order of the grating was chosen due to the low fluorescence yield signal.…”

Section: Methodsmentioning

confidence: 99%

Assistance of the Iron Porphyrin Ligands to the Binding Interaction between the Fe Center and Small Molecules in Solution

et al. 2014

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Solute-solvent electronic structure interactions of iron-porphyrin at very low concentration in dichloromethane (CH 2 Cl 2 ) liquid solution are reported. Two iron porphyrin complexes are investigated here, iron octaethylporphyrin chloride (FeOEP-Cl) and iron tetraphenylporphyrin chloride (FeTPP-Cl), using X-ray absorption and emission spectroscopy at the Fe L 2,3 edge, and spectra are interpreted with the help of density functional theory/restricted open shell configuration interaction singles (DFT/ROCIS) calculations. It is argued that the Fe center of FeOEP-Cl is more capable of binding small solvent molecules, exemplified here for Cl 2 CH 2 , than FeTPP-Cl in solution. The proposed binding mechanism is through the assistance of the dipole interaction between the porphyrin-ligand system and the solvent molecule, in a situation where the ligand structure and arrangement maximize the binding interactions. Our studies demonstrate that even small ligands, depending on their structure and arrangement, can have considerable effects on porphyrin's metal center chemistry in liquid solution.

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On the origin of dips in total fluorescence yield X-ray absorption spectra: Partial and inverse partial fluorescence yield at the L-edge of cobalt aqueous solution

Cited by 23 publications

References 21 publications

Dissecting Local Atomic and Intermolecular Interactions of Transition-Metal Ions in Solution with Selective X-ray Spectroscopy

Dissecting Local Atomic and Intermolecular Interactions of Transition-Metal Ions in Solution with Selective X-ray Spectroscopy

Electrochemical flowcell for in-situ investigations by soft x-ray absorption and emission spectroscopy

Assistance of the Iron Porphyrin Ligands to the Binding Interaction between the Fe Center and Small Molecules in Solution

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