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Seymour J, Gousseva E, Large A, Held G, Hein D, Wartner G, Quevedo W, Seidel R, Kolbeck C, Clarke CJ, Fogarty R, Bourne R, Bennett R, Palgrave R, Hunt PA, Lovelock KRJ. Resonant Electron Spectroscopy: Identification of Atomic Contributions to Valence States. Faraday Discuss 2022; 236:389-411. [DOI: 10.1039/d1fd00117e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Valence electronic structure is crucial for understanding and predicting reactivity. Valence non-resonant X-ray photoelectron spectroscopy (NRXPS) provides a direct method for probing the overall valence electronic structure. However, it is...
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2
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Malerz S, Trinter F, Hergenhahn U, Ghrist A, Ali H, Nicolas C, Saak CM, Richter C, Hartweg S, Nahon L, Lee C, Goy C, Neumark DM, Meijer G, Wilkinson I, Winter B, Thürmer S. Low-energy constraints on photoelectron spectra measured from liquid water and aqueous solutions. Phys Chem Chem Phys 2021; 23:8246-8260. [PMID: 33710216 DOI: 10.1039/d1cp00430a] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report on the effects of electron collision and indirect ionization processes, occurring at photoexcitation and electron kinetic energies well below 30 eV, on the photoemission spectra of liquid water. We show that the nascent photoelectron spectrum and, hence, the inferred electron binding energy can only be accurately determined if electron energies are large enough that cross sections for quasi-elastic scattering processes, such as vibrational excitation, are negligible. Otherwise, quasi-elastic scattering leads to strong, down-to-few-meV kinetic energy scattering losses from the direct photoelectron features, which manifest in severely distorted intrinsic photoelectron peak shapes. The associated cross-over point from predominant (known) electronically inelastic to quasi-elastic scattering seems to arise at surprisingly large electron kinetic energies, of approximately 10-14 eV. Concomitantly, we present evidence for the onset of indirect, autoionization phenomena (occurring via superexcited states) within a few eV of the primary and secondary ionization thresholds. These processes are inferred to compete with the direct ionization channels and primarily produce low-energy photoelectrons at photon and electron impact excitation energies below ∼15 eV. Our results highlight that vibrational inelastic electron scattering processes and neutral photoexcitation and autoionization channels become increasingly important when photon and electron kinetic energies are decreased towards the ionization threshold. Correspondingly, we show that for neat water and aqueous solutions, great care must be taken when quantitatively analyzing photoelectron spectra measured too close to the ionization threshold. Such care is essential for the accurate determination of solvent and solute ionization energies as well as photoelectron branching ratios and peak magnitudes.
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Affiliation(s)
- Sebastian Malerz
- Molecular Physics Department, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
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Dupuy R, Richter C, Winter B, Meijer G, Schlögl R, Bluhm H. Core level photoelectron spectroscopy of heterogeneous reactions at liquid-vapor interfaces: Current status, challenges, and prospects. J Chem Phys 2021; 154:060901. [PMID: 33588531 DOI: 10.1063/5.0036178] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Liquid-vapor interfaces, particularly those between aqueous solutions and air, drive numerous important chemical and physical processes in the atmosphere and in the environment. X-ray photoelectron spectroscopy is an excellent method for the investigation of these interfaces due to its surface sensitivity, elemental and chemical specificity, and the possibility to obtain information on the depth distribution of solute and solvent species in the interfacial region. In this Perspective, we review the progress that was made in this field over the past decades and discuss the challenges that need to be overcome for investigations of heterogeneous reactions at liquid-vapor interfaces under close-to-realistic environmental conditions. We close with an outlook on where some of the most exciting and promising developments might lie in this field.
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Affiliation(s)
- Rémi Dupuy
- Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Clemens Richter
- Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Bernd Winter
- Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Gerard Meijer
- Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Robert Schlögl
- Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Hendrik Bluhm
- Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, D-14195 Berlin, Germany
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Mudryk KD, Seidel R, Winter B, Wilkinson I. The electronic structure of the aqueous permanganate ion: aqueous-phase energetics and molecular bonding studied using liquid jet photoelectron spectroscopy. Phys Chem Chem Phys 2020; 22:20311-20330. [PMID: 32895669 DOI: 10.1039/d0cp04033a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Permanganate aqueous solutions, MnO4-(aq.), were studied using liquid-micro-jet-based soft X-ray non-resonant and resonant photoelectron spectroscopy to determine valence and core-level binding energies. To identify possible differences in the energetics between the aqueous bulk and the solution-gas interface, non-resonant spectra were recorded at two different probing depths. Similar experiments were performed with different counter ions, Na+ and K+, with the two solutions yielding indistinguishable anion electron binding energies. Our resonant photoelectron spectroscopy measurements, performed near the Mn LII,III- and O K-edges, selectively probed valence charge distributions between the Mn metal center, O ligands, and first solvation shell in the aqueous bulk. Associated resonantly-enhanced solute ionisation signals revealed hybridisation of the solute constituents' atomic orbitals, including the inner valence Mn 3p and O 2s. We identified intermolecular coulombic decay relaxation processes following resonant X-ray excitation of the solute that highlight valence MnO4-(aq.)-H2O(l) electronic couplings. Furthermore, our results allowed us to infer oxidative reorganisation energies of MnO4˙(aq.) and adiabatic valence ionisation energies of MnO4-(aq.), revealing the Gibbs free energy of oxidation and permitting estimation of the vertical electron affinity of MnO4˙(aq.). Finally, the Gibbs free energy of hydration of isolated MnO4- was determined. Our results and analysis allowed a near-complete binding-energy-scaled MnO4-(aq.) molecular orbital and a valence energy level diagram to be produced for the MnO4-(aq.)/MnO4˙(aq.) system. Cumulatively, our mapping of the aqueous-phase electronic structure of MnO4- is expected to contribute to a deeper understanding of the exceptional redox properties of this widely applied aqueous transition-metal complex ion.
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Affiliation(s)
- Karen D Mudryk
- Locally-Sensitive & Time-Resolved Spectroscopy, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. and Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
| | - Robert Seidel
- Operando Interfacial Photochemistry, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany and Fachbereich Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany
| | - Bernd Winter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Iain Wilkinson
- Locally-Sensitive & Time-Resolved Spectroscopy, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany.
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Fogarty RM, Palgrave RG, Bourne RA, Handrup K, Villar-Garcia IJ, Payne DJ, Hunt PA, Lovelock KRJ. Electron spectroscopy of ionic liquids: experimental identification of atomic orbital contributions to valence electronic structure. Phys Chem Chem Phys 2019; 21:18893-18910. [PMID: 31441923 DOI: 10.1039/c9cp02200g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The atomic contributions to valence electronic structure for 37 ionic liquids (ILs) are identified using a combination of variable photon energy XPS, resonant Auger electron spectroscopy (RAES) and a subtraction method. The ILs studied include a diverse range of cationic and anionic structural moieties. We introduce a new parameter for ILs, the energy difference between the energies of the cationic and anionic highest occupied fragment orbitals (HOFOs), which we use to identify the highest occupied molecular orbital (HOMO). The anion gave rise to the HOMO for 25 of the 37 ILs studied here. For 10 of the ILs, the energies of the cationic and anionic HOFOs were the same (within experimental error); therefore, it could not be determined whether the HOMO was from the cation or the anion. For two of the ILs, the HOMO was from the cation and not from the anion; consequently it is energetically more favourable to remove an electron from the cation than the anion for these two ILs. In addition, we used a combination of area normalisation and subtraction of XP spectra to produce what are effectively XP spectra for individual ions; this was achieved for 10 cations and 14 anions.
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Affiliation(s)
| | | | - Richard A Bourne
- Institute of Process Research and Development, Schools of Chemistry and Chemical and Process Engineering, University of Leeds, UK
| | | | | | - David J Payne
- Department of Materials, Imperial College London, UK
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Ali H, Seidel R, Pohl MN, Winter B. Molecular species forming at the α-Fe 2O 3 nanoparticle-aqueous solution interface. Chem Sci 2018; 9:4511-4523. [PMID: 29896394 PMCID: PMC5961451 DOI: 10.1039/c7sc05156e] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 04/19/2018] [Indexed: 11/22/2022] Open
Abstract
We report on electronic structure measurements of the interface between hematite nanoparticles (6 nm diameter) and aqueous solutions. Using soft X-ray photoelectron spectroscopy from a liquid microjet we detect valence and core-level photoelectrons as well as Auger electrons from liquid water, from the nanoparticle-water interface, and from the interior of the aqueous-phase nanoparticles. Most noteworthy, the method is shown to be sufficiently sensitive for the detection of adsorbed hydroxyl species, resulting from H2O dissociation at the nanoparticle surface in aqueous solution. We obtain signal from surface OH from resonant, non-resonant, and from so-called partial-electron-yield X-ray absorption (PEY-XA) spectra. In addition, we report resonant photoelectron measurements at the iron 2p excitation. The respective Fe iron 2p3/2 edge (L3-edge) PEY-XA spectra exhibit two main absorption peaks with their energies being sensitive to the chemical environment of the Fe3+ ions at the nanoparticle-solution interface. This manifests in the 10Dq value which is a measure of the ligand-field strength. Furthermore, an observed intensity variation of the pre-peak, when comparing the PEY-XA spectra for different iron Auger-decay channels, can be assigned to different extents of electron delocalization. From the experimental fraction of local versus non-local autoionization signals we then find a very fast, approximately 1 fs, charge transfer time from interfacial Fe3+ into the environment. The present study, which is complementary to ambient-pressure photoemission studies on solid-electrolyte systems, also highlights the multiple aspects of photoemission that need to be explored for a full characterization of the transition-metal-oxide nanoparticle surface in aqueous phase.
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Affiliation(s)
- Hebatallah Ali
- Fritz-Haber-Institut der Max-Planck-Gesellschaft , Faradayweg 4-6 , D-14195 Berlin , Germany .
- Fachbereich Physik , Freie Universität Berlin , Arnimallee 14 , D-14195 Berlin , Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie , Albert-Einstein-Straße 15 , D-12489 Berlin , Germany
| | - Robert Seidel
- Helmholtz-Zentrum Berlin für Materialien und Energie , Albert-Einstein-Straße 15 , D-12489 Berlin , Germany
- Humboldt-Universität zu Berlin , Department of Chemistry , Brook-Taylor-Str. 2 , D-12489 Berlin , Germany
| | - Marvin N Pohl
- Fritz-Haber-Institut der Max-Planck-Gesellschaft , Faradayweg 4-6 , D-14195 Berlin , Germany .
- Fachbereich Physik , Freie Universität Berlin , Arnimallee 14 , D-14195 Berlin , Germany
| | - Bernd Winter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft , Faradayweg 4-6 , D-14195 Berlin , Germany .
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Seidel R, Pohl MN, Ali H, Winter B, Aziz EF. Advances in liquid phase soft-x-ray photoemission spectroscopy: A new experimental setup at BESSY II. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2017; 88:073107. [PMID: 28764540 DOI: 10.1063/1.4990797] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A state-of-the-art experimental setup for soft X-ray photo- and Auger-electron spectroscopy from liquid phase has been built for operation at the synchrotron-light facility BESSY II, Berlin. The experimental station is named SOL3, which is derived from solid, solution, and solar, and refers to the aim of studying solid-liquid interfaces, optionally irradiated by photons in the solar spectrum. SOL3 is equipped with a high-transmission hemispherical electron analyzer for detecting electrons emitted from small molecular aggregates, nanoparticles, or biochemical molecules and their components in (aqueous) solutions, either in vacuum or in an ambient pressure environment. In addition to conventional energy-resolved electron detection, SOL3 enables detection of electron angular distributions by the combination of a ±11° acceptance angle of the electron analyzer and a rotation of the analyzer in the polarization plane of the incoming synchrotron-light beam. The present manuscript describes the technical features of SOL3, and we also report the very first measurements of soft-X-ray photoemission spectra from a liquid microjet of neat liquid water and of TiO2-nanoparticle aqueous solution obtained with this new setup, highlighting the necessity for state-of-the-art electron detection.
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Affiliation(s)
- Robert Seidel
- Helmholtz-Zentrum Berlin für Materialien und Energie, Methods for Material Development, Albert-Einstein-Straße 15, D-12489 Berlin, Germany
| | - Marvin N Pohl
- Helmholtz-Zentrum Berlin für Materialien und Energie, Methods for Material Development, Albert-Einstein-Straße 15, D-12489 Berlin, Germany
| | - Hebatallah Ali
- Helmholtz-Zentrum Berlin für Materialien und Energie, Methods for Material Development, Albert-Einstein-Straße 15, D-12489 Berlin, Germany
| | - Bernd Winter
- Helmholtz-Zentrum Berlin für Materialien und Energie, Methods for Material Development, Albert-Einstein-Straße 15, D-12489 Berlin, Germany
| | - Emad F Aziz
- Helmholtz-Zentrum Berlin für Materialien und Energie, Methods for Material Development, Albert-Einstein-Straße 15, D-12489 Berlin, Germany
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Chemical bonding in aqueous hexacyano cobaltate from photon- and electron-detection perspectives. Sci Rep 2017; 7:40811. [PMID: 28098216 PMCID: PMC5241694 DOI: 10.1038/srep40811] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 12/12/2016] [Indexed: 01/22/2023] Open
Abstract
The electronic structure of the [Co(CN)6]3- complex dissolved in water is studied using X-ray spectroscopy techniques. By combining electron and photon detection methods from the solutions ionized or excited by soft X-rays we experimentally identify chemical bonding between the metal center and the CN ligand. Non-resonant photoelectron spectroscopy provides solute electron binding energies, and nitrogen 1 s and cobalt 2p resonant core-level photoelectron spectroscopy identifies overlap between metal and ligand orbitals. By probing resonances we are able to qualitatively determine the ligand versus metal character of the respective occupied and non-occupied orbitals, purely by experiment. For the same excitations we also detect the emitted X-rays, yielding the complementary resonant inelastic X-ray scattering spectra. For a quantitative interpretation of the spectra, we perform theoretical electronic-structure calculations. The latter provide both orbital energies and orbital character which are found to be in good agreement with experimental energies and with experimentally inferred orbital mixing. We also report calculated X-ray absorption spectra, which in conjunction with our orbital-structure analysis, enables us to quantify various bonding interactions with a particular focus on the water-solvent - ligand interaction and the strength of π-backbonding between metal and ligand.
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Seidel R, Kraffert K, Kabelitz A, Pohl MN, Kraehnert R, Emmerling F, Winter B. Detection of the electronic structure of iron-(iii)-oxo oligomers forming in aqueous solutions. Phys Chem Chem Phys 2017; 19:32226-32234. [DOI: 10.1039/c7cp06945f] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electronic structure of the small iron-oxo oligomers forming in iron-(iii) aqueous solutions is determined from liquid jet photoelectron spectroscopy.
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Affiliation(s)
- Robert Seidel
- Helmholtz-Zentrum Berlin für Materialien und Energie, Institute for Material Development
- Albert-Einstein-Strasse 15
- D-12489 Berlin
- Germany
- Humboldt-Universität zu Berlin
| | - Katrin Kraffert
- Technische Universität Berlin
- Department of Chemistry
- Strasse des 17. Juni 124
- D-10623 Berlin
- Germany
| | - Anke Kabelitz
- Humboldt-Universität zu Berlin
- Department of Chemistry
- Brook-Taylor-Str. 2
- D-12489 Berlin
- Germany
| | - Marvin N. Pohl
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- Faradayweg 4-6
- D-14195 Berlin
- Germany
| | - Ralph Kraehnert
- Technische Universität Berlin
- Department of Chemistry
- Strasse des 17. Juni 124
- D-10623 Berlin
- Germany
| | - Franziska Emmerling
- BAM Federal Institute for Materials Research and Testing
- Richard-Willstätter Strasse 11
- D-12489 Berlin
- Germany
| | - Bernd Winter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- Faradayweg 4-6
- D-14195 Berlin
- Germany
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10
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Gaiduk AP, Govoni M, Seidel R, Skone JH, Winter B, Galli G. Photoelectron Spectra of Aqueous Solutions from First Principles. J Am Chem Soc 2016; 138:6912-5. [PMID: 27105336 DOI: 10.1021/jacs.6b00225] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present a combined computational and experimental study of the photoelectron spectrum of a simple aqueous solution of NaCl. Measurements were conducted on microjets, and first-principles calculations were performed using hybrid functionals and many-body perturbation theory at the G0W0 level, starting with wave functions computed in ab initio molecular dynamics simulations. We show excellent agreement between theory and experiments for the positions of both the solute and solvent excitation energies on an absolute energy scale and for peak intensities. The best comparison was obtained using wave functions obtained with dielectric-dependent self-consistent and range-separated hybrid functionals. Our computational protocol opens the way to accurate, predictive calculations of the electronic properties of electrolytes, of interest to a variety of energy problems.
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Affiliation(s)
- Alex P Gaiduk
- Institute for Molecular Engineering, The University of Chicago , Chicago, Illinois 60637, United States
| | - Marco Govoni
- Institute for Molecular Engineering, The University of Chicago , Chicago, Illinois 60637, United States.,Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
| | - Robert Seidel
- Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie , D-12489 Berlin, Germany
| | - Jonathan H Skone
- Institute for Molecular Engineering, The University of Chicago , Chicago, Illinois 60637, United States
| | - Bernd Winter
- Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie , D-12489 Berlin, Germany
| | - Giulia Galli
- Institute for Molecular Engineering, The University of Chicago , Chicago, Illinois 60637, United States.,Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
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Golnak R, Xiao J, Atak K, Unger I, Seidel R, Winter B, Aziz EF. Undistorted X-ray Absorption Spectroscopy Using s-Core-Orbital Emissions. J Phys Chem A 2016; 120:2808-14. [PMID: 27101344 DOI: 10.1021/acs.jpca.6b01699] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Detection of secondary emissions, fluorescence yield (FY), or electron yield (EY), originating from the relaxation processes upon X-ray resonant absorption has been widely adopted for X-ray absorption spectroscopy (XAS) measurements when the primary absorption process cannot be probed directly in transmission mode. Various spectral distortion effects inherent in the relaxation processes and in the subsequent transportation of emitted particles (electron or photon) through the sample, however, undermine the proportionality of the emission signals to the X-ray absorption coefficient. In the present study, multiple radiative (FY) and nonradiative (EY) decay channels have been experimentally investigated on a model system, FeCl3 aqueous solution, at the excitation energy of the Fe L-edge. The systematic comparisons between the experimental spectra taken from various decay channels, as well as the comparison with the theoretically simulated Fe L-edge XA spectrum that involves only the absorption process, indicate that the detection of the Fe 3s → 2p partial fluorescence yield (PFY) gives rise to the true Fe L-edge XA spectrum. The two key characteristics generalized from this particular decay channel-zero orbital angular momentum (i.e., s orbital) and core-level emission-set a guideline for obtaining undistorted X-ray absorption spectra in the future.
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Affiliation(s)
- Ronny Golnak
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) , Albert-Einstein-Strasse 15, D-12489 Berlin, Germany.,Department of Chemistry, Free University Berlin , Takustrasse 3, 14195 Berlin, Germany
| | - Jie Xiao
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) , Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - Kaan Atak
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) , Albert-Einstein-Strasse 15, D-12489 Berlin, Germany.,Department of Physics, Free University Berlin , Arnimallee 14, 14195 Berlin, Germany
| | - Isaak Unger
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) , Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - Robert Seidel
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) , Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - Bernd Winter
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) , Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - Emad F Aziz
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) , Albert-Einstein-Strasse 15, D-12489 Berlin, Germany.,Department of Physics, Free University Berlin , Arnimallee 14, 14195 Berlin, Germany
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12
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Seidel R, Winter B, Bradforth SE. Valence Electronic Structure of Aqueous Solutions: Insights from Photoelectron Spectroscopy. Annu Rev Phys Chem 2016; 67:283-305. [PMID: 27023757 DOI: 10.1146/annurev-physchem-040513-103715] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The valence orbital electron binding energies of water and of embedded solutes are crucial quantities for understanding chemical reactions taking place in aqueous solution, including oxidation/reduction, transition-metal coordination, and radiation chemistry. Their experimental determination based on liquid-photoelectron spectroscopy using soft X-rays is described, and we provide an overview of valence photoelectron spectroscopy studies reported to date. We discuss principal experimental aspects and several theoretical approaches to compute the measured binding energies of the least tightly bound molecular orbitals. Solutes studied are presented chronologically, from simple electrolytes, via transition-metal ion solutions and several organic and inorganic molecules, to biologically relevant molecules, including aqueous nucleotides and their components. In addition to the lowest vertical ionization energies, the measured valence photoelectron spectra also provide information on adiabatic ionization energies and reorganization energies for the oxidation (ionization) half-reaction. For solutes with low solubility, resonantly enhanced ionization provides a promising alternative pathway.
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Affiliation(s)
- Robert Seidel
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin, D-12489 Berlin, Germany; ,
| | - Bernd Winter
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin, D-12489 Berlin, Germany; ,
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482;
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