TY  - JOUR
A1  - Eckert, Sebastian
A1  - Vaz da Cruz, Vinícius
A1  - Ochmann, Miguel
A1  - Ahnen, Inga von
A1  - Föhlisch, Alexander
A1  - Huse, Nils
T1  - Breaking the symmetry of pyrimidine
BT  - solvent effects and core-excited state dynamics
JF  - The journal of physical chemistry letters
N2  - Symmetry and its breaking crucially define the chemical properties of molecules and their functionality. Resonant inelastic X-ray scattering is a local electronic structure probe reporting on molecular symmetry and its dynamical breaking within the femtosecond scattering duration. Here, we study pyrimidine, a system from the C-2v point group, in an aqueous solution environment, using scattering though its 2a(2) resonance. Despite the absence of clean parity selection rules for decay transitions from in-plane orbitals, scattering channels including decay from the 7b(2) and 11a(1) orbitals with nitrogen lone pair character are a direct probe for molecular symmetry. Computed spectra of explicitly solvated molecules sampled from a molecular dynamics simulation are combined with the results of a quantum dynamical description of the X-ray scattering process. We observe dominant signatures of core-excited Jahn-Teller induced symmetry breaking for resonant excitation. Solvent contributions are separable by shortening of the effective scattering duration through excitation energy detuning.
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jpclett.1c01865
SN  - 1948-7185
VL  - 12
IS  - 35
SP  - 8637
EP  - 8643
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ochmann, Miguel
A1  - Vaz da Cruz, Vinicius
A1  - Eckert, Sebastian
A1  - Huse, Nils
A1  - Föhlisch, Alexander
T1  - R-Group stabilization in methylated formamides observed by resonant inelastic X-ray scattering
JF  - Chemical communications: ChemComm
N2  - The inherent stability of methylated formamides is traced to a stabilization of the deep-lying sigma-framework by resonant inelastic X-ray scattering at the nitrogen K-edge. Charge transfer from the amide nitrogen to the methyl groups underlie this stabilization mechanism that leaves the aldehyde group essentially unaltered and explains the stability of secondary and tertiary amides.
Y1  - 2022
U6  - https://doi.org/10.1039/d2cc00053a
SN  - 1359-7345
SN  - 1364-548X
VL  - 58
IS  - 63
SP  - 8834
EP  - 8837
PB  - The Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Jay, Raphael M.
A1  - Eckert, Sebastian
A1  - Mitzner, Rolf
A1  - Fondell, Mattis
A1  - Föhlisch, Alexander
T1  - Quantitative evaluation of transient valence orbital occupations in a 3d transition metal complex as seen from the metal and ligand perspective
JF  - Chemical physics letters
N2  - It is demonstrated for the case of photo-excited ferrocyanide how time-resolved soft X-ray absorption spectroscopy in transmission geometry at the ligand K-edge and metal L-3-edge provides quantitatively equivalent valence electronic structure information, where signatures of photo-oxidation are assessed locally at the metal as well as the ligand. This allows for a direct and independent quantification of the number of photo-oxidized molecules at two soft X-ray absorption edges highlighting the sensitivity of X-ray absorption spectroscopy to the valence orbital occupation of 3d transition metal complexes throughout the soft X-ray range.
KW  - iron cyanides
KW  - photochemistry
KW  - soft X-ray absorption
Y1  - 2020
U6  - https://doi.org/10.1016/j.cplett.2020.137681
SN  - 0009-2614
SN  - 1873-4448
VL  - 754
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Vaz da Cruz, Vinícius
A1  - Eckert, Sebastian
A1  - Föhlisch, Alexander
T1  - TD-DFT simulations of K-edge resonant inelastic X-ray scattering within the restricted subspace approximation
JF  - Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies
N2  - A scheme for simulations of resonant inelastic X-ray scattering (RIXS) cross-sections within time-dependent density functional theory (TD-DFT) applying the restricted subspace approximation (RSA) is presented. Therein both occupied core and valence Kohn-Sham orbitals are included in the donor-space, while the accepting virtual orbital space in the linear response TD-DFT equations is restricted to efficiently compute both the valence- and core-excited states of the many electron system. This yields a consistent description of all states contributing to the RIXS scattering process within a single calculation. The introduced orbital truncation allows to automatize the method and facilitates RIXS simulations for systems considerably larger than ones accessible with wave-function based methods. Using the nitrogen K-edge RIXS spectra of 2-thiopyridone and its deprotonated anion as a showcase, the method is benchmarked for different exchange-correlation functionals, the impact of the RSA is evaluated, and the effects of explicit solvation are discussed. Improvements compared to simulations in the frozen orbital approximation are also assessed. The general applicability of the framework is further tested by comparison to experimental data from the literature. The use of TD-DFT core-excited states to the calculation of vibrationally resolved RIXS spectra is also investigated by combining potential energy scans along relevant coordinates with wave packet simulations.
Y1  - 2020
U6  - https://doi.org/10.1039/d0cp04726k
SN  - 1463-9076
SN  - 1463-9084
VL  - 23
IS  - 3
SP  - 1835
EP  - 1848
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Eckert, Sebastian
A1  - Mascarenhas, Eric Johnn
A1  - Mitzner, Rolf
A1  - Jay, Raphael Martin
A1  - Pietzsch, Annette
A1  - Fondell, Mattis
A1  - Vaz da Cruz, Vinicius
A1  - Föhlisch, Alexander
T1  - From the free ligand to the transition metal complex
BT  - FeEDTA(-) formation seen at ligand K-Edges
JF  - Inorganic chemistry
N2  - Chelating agents are an integral part of transition metal complex chemistry with broad biological and industrial relevance. The hexadentate chelating agent ethylenediaminetetraacetic acid (EDTA) has the capability to bind to metal ions at its two nitrogen and four of its carboxylate oxygen sites. We use resonant inelastic X-ray scattering at the 1s absorption edge of the aforementioned elements in EDTA and the iron(III)-EDTA complex to investigate the impact of the metal-ligand bond formation on the electronic structure of EDTA. Frontier orbital distortions, occupation changes, and energy shifts through metal- ligand bond formation are probed through distinct spectroscopic signatures.
KW  - Energy
KW  - Ligands
KW  - Metals
KW  - Nitrogen
KW  - Oxygen
Y1  - 2022
U6  - https://doi.org/10.1021/acs.inorgchem.2c00789
SN  - 0020-1669
SN  - 1520-510X
VL  - 61
IS  - 27
SP  - 10321
EP  - 10328
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Vaz da Cruz, Vinicius
A1  - Büchner, Robby
A1  - Fondell, Mattis
A1  - Pietzsch, Annette
A1  - Eckert, Sebastian
A1  - Föhlisch, Alexander
T1  - Targeting individual tautomers in equilibrium by resonant inelastic X-ray scattering
JF  - The journal of physical chemistry letters
N2  - Tautomerism is one of the most important forms of isomerism, owing to the facile interconversion between species and the large differences in chemical properties introduced by the proton transfer connecting the tautomers. Spectroscopic techniques are often used for the characterization of tautomers. In this context, separating the overlapping spectral response of coexisting tautomers is a long-standing challenge in chemistry. Here, we demonstrate that by using resonant inelastic X-ray scattering tuned to the core excited states at the site of proton exchange between tautomers one is able to experimentally disentangle the manifold of valence excited states of each tautomer in a mixture. The technique is applied to the prototypical keto-enol equilibrium of 3-hydroxypyridine in aqueous solution. We detect transitions from the occupied orbitals into the LUMO for each tautomer in solution, which report on intrinsic and hydrogen-bond-induced orbital polarization within the pi and sigma manifolds at the proton-transfer site.
KW  - Equilibrium
KW  - Molecular structure
KW  - Molecules
KW  - Nitrogen
KW  - Solvents
Y1  - 2022
U6  - https://doi.org/10.1021/acs.jpclett.1c03453
SN  - 1948-7185
VL  - 13
IS  - 10
SP  - 2459
EP  - 2466
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Mascarenhas, Eric Johnn
A1  - Fondell, Mattis
A1  - Büchner, Robby
A1  - Eckert, Sebastian
A1  - Vaz da Cruz, Vinícius
A1  - Föhlisch, Alexander
T1  - Photo-induced ligand substitution of Cr(CO)(6) in 1-pentanol probed by time resolved X-ray absorption spectroscopy
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - Cr(CO)(6) was investigated by X-ray absorption spectroscopy. The spectral signature at the metal edge provides information about the back-bonding of the metal in this class of complexes. Among the processes it participates in is ligand substitution in which a carbonyl ligand is ejected through excitation to a metal to ligand charge transfer (MLCT) band. The unsaturated carbonyl Cr(CO)(5) is stabilized by solution media in square pyramidal geometry and further reacts with the solvent. Multi-site-specific probing after photoexcitation was used to investigate the ligand substitution photoreaction process which is a common first step in catalytic processes involving metal carbonyls. The data were analysed with the aid of TD-DFT computations for different models of photoproducts and signatures for ligand rearrangement after substitution were found. The rearrangement was found to occur in about 790 ps in agreement with former studies of the photoreaction.
Y1  - 2022
U6  - https://doi.org/10.1039/d1cp05834g
SN  - 1463-9076
SN  - 1463-9084
VL  - 24
IS  - 30
SP  - 17979
EP  - 17985
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Pietzsch, Annette
A1  - Niskanen, Johannes
A1  - Vaz da Cruz, Vinicius
A1  - Büchner, Robby
A1  - Eckert, Sebastian
A1  - Fondell, Mattis
A1  - Jay, Raphael Martin
A1  - Lu, Xingye
A1  - McNally, Daniel
A1  - Schmitt, Thorsten
A1  - Föhlisch, Alexander
T1  - Cuts through the manifold of molecular H2O potential energy surfaces in liquid water at ambient conditions
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - The fluctuating hydrogen bridge bonded network of liquid water at ambient conditions entails a varied ensemble of the underlying constituting H2O molecular moieties. This is mirrored in a manifold of the H2O molecular potentials. Subnatural line width resonant inelastic X-ray scattering allowed us to quantify the manifold of molecular potential energy surfaces along the H2O symmetric normal mode and the local asymmetric O-H bond coordinate up to 1 and 1.5 angstrom, respectively. The comparison of the single H2O molecular potentials and spectroscopic signatures with the ambient conditions liquid phase H2O molecular potentials is done on various levels. In the gas phase, first principles, Morse potentials, and stepwise harmonic potential reconstruction have been employed and benchmarked. In the liquid phase the determination of the potential energy manifold along the local asymmetric O-H bond coordinate from resonant inelastic X-ray scattering via the bound state oxygen ls to 4a(1) resonance is treated within these frameworks. The potential energy surface manifold along the symmetric stretch from resonant inelastic X-ray scattering via the oxygen 1 s to 2b(2) resonance is based on stepwise harmonic reconstruction. We find in liquid water at ambient conditions H2O molecular potentials ranging from the weak interaction limit to strongly distorted potentials which are put into perspective to established parameters, i.e., intermolecular O-H, H-H, and O-O correlation lengths from neutron scattering.
KW  - water
KW  - potential ene rgy surface
KW  - RIXS
Y1  - 2022
U6  - https://doi.org/10.1073/pnas.2118101119
SN  - 1091-6490
VL  - 119
IS  - 28
PB  - National Acad. of Sciences
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Jay, Raphael M.
A1  - Vaz da Cruz, Vinicius
A1  - Eckert, Sebastian
A1  - Fondell, Mattis
A1  - Mitzner, Rolf
A1  - Föhlisch, Alexander
T1  - Probing solute-solvent interactions of transition metal complexes using L-edge absorption spectroscopy
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - In order to tailor solution-phase chemical reactions involving transition metal complexes, it is critical to understand how their valence electronic charge distributions are affected by the solution environment. Here, solute-solvent interactions of a solvatochromic mixed-ligand iron complex were investigated using X-ray absorption spectroscopy at the transition metal L-2,L-3-edge. Due to the selectivity of the corresponding core excitations to the iron 3d orbitals, the method grants direct access to the valence electronic structure around the iron center and its response to interactions with the solvent environment. A linear increase of the total L-2,L-3-edge absorption cross section as a function of the solvent Lewis acidity is revealed. The effect is caused by relative changes in different metal-ligand-bonding channels, which preserve local charge densities while increasing the density of unoccupied states around the iron center. These conclusions are corroborated by a combination of molecular dynamics and spectrum simulations based on time-dependent density functional theory. The simulations reproduce the spectral trends observed in the X-ray but also optical absorption experiments. Our results underscore the importance of solute-solvent interactions when aiming for an accurate description of the valence electronic structure of solvated transition metal complexes and demonstrate how L-2,L-3-edge absorption spectroscopy can aid in understanding the impact of the solution environment on intramolecular covalency and the electronic charge distribution.
KW  - basis-sets
KW  - charge-transfer
KW  - density
KW  - dynamics
KW  - electron localization
KW  - iron
KW  - solvation
KW  - spin-crossover
KW  - tranfer excited-state
KW  - x-ray-absorption
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jpcb.0c00638
SN  - 1520-6106
SN  - 1520-5207
VL  - 124
IS  - 27
SP  - 5636
EP  - 5645
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Couto, Rafael C.
A1  - Cruz, Vinicius V.
A1  - Ertan, Emelie
A1  - Eckert, Sebastian
A1  - Fondell, Mattis
A1  - Dantz, Marcus
A1  - Kennedy, Brian
A1  - Schmitt, Thorsten
A1  - Pietzsch, Annette
A1  - Guimaraes, Freddy F.
A1  - Agren, Hans
A1  - Odelius, Michael
A1  - Kimberg, Victor
A1  - Föhlisch, Alexander
T1  - Selective gating to vibrational modes through resonant X-ray scattering
JF  - Nature Communications
N2  - The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations.
Y1  - 2017
U6  - https://doi.org/10.1038/ncomms14165
SN  - 2041-1723
VL  - 8
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Eckert, Sebastian
A1  - Vaz da Cruz, Vinicius
A1  - Ertan, Emelie
A1  - Ignatova, Nina
A1  - Polyutov, Sergey
A1  - Couto, Rafael C.
A1  - Fondell, Mattis
A1  - Dantz, Marcus
A1  - Kennedy, Brian
A1  - Schmitt, Thorsten
A1  - Pietzsch, Annette
A1  - Odelius, Michael
A1  - Föhlisch, Alexander
T1  - One-dimensional cuts through multidimensional potential-energy surfaces by tunable x rays
JF  - Physical review : A, Atomic, molecular, and optical physics
N2  - The concept of the potential-energy surface (PES) and directional reaction coordinates is the backbone of our description of chemical reaction mechanisms. Although the eigenenergies of the nuclear Hamiltonian uniquely link a PES to its spectrum, this information is in general experimentally inaccessible in large polyatomic systems. This is due to (near) degenerate rovibrational levels across the parameter space of all degrees of freedom, which effectively forms a pseudospectrum given by the centers of gravity of groups of close-lying vibrational levels. We show here that resonant inelastic x-ray scattering (RIXS) constitutes an ideal probe for revealing one-dimensional cuts through the ground-state PES of molecular systems, even far away from the equilibrium geometry, where the independent-mode picture is broken. We strictly link the center of gravity of close-lying vibrational peaks in RIXS to a pseudospectrum which is shown to coincide with the eigenvalues of an effective one-dimensional Hamiltonian along the propagation coordinate of the core-excited wave packet. This concept, combined with directional and site selectivity of the core-excited states, allows us to experimentally extract cuts through the ground-state PES along three complementary directions for the showcase H2O molecule.
Y1  - 2018
U6  - https://doi.org/10.1103/PhysRevA.97.053410
SN  - 2469-9926
SN  - 2469-9934
VL  - 97
IS  - 5
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Ertan, Emelie
A1  - Savchenko, Viktoriia
A1  - Ignatova, Nina
A1  - Vaz da Cruz, Vinicius
A1  - Couto, Rafael C.
A1  - Eckert, Sebastian
A1  - Fondell, Mattis
A1  - Dantz, Marcus
A1  - Kennedy, Brian
A1  - Schmitt, Thorsten
A1  - Pietzsch, Annette
A1  - Föhlisch, Alexander
A1  - Odelius, Michael
A1  - Kimberg, Victor
T1  - Ultrafast dissociation features in RIXS spectra of the water molecule
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - In this combined theoretical and experimental study we report on an analysis of the resonant inelastic X-ray scattering (RIXS) spectra of gas phase water via the lowest dissociative core-excited state |1s−1O4a11〉. We focus on the spectral feature near the dissociation limit of the electronic ground state. We show that the narrow atomic-like peak consists of the overlapping contribution from the RIXS channels back to the ground state and to the first valence excited state |1b−114a11〉 of the molecule. The spectral feature has signatures of ultrafast dissociation (UFD) in the core-excited state, as we show by means of ab initio calculations and time-dependent nuclear wave packet simulations. We show that the electronically elastic RIXS channel gives substantial contribution to the atomic-like resonance due to the strong bond length dependence of the magnitude and orientation of the transition dipole moment. By studying the RIXS for an excitation energy scan over the core-excited state resonance, we can understand and single out the molecular and atomic-like contributions in the decay to the lowest valence-excited state. Our study is complemented by a theoretical discussion of RIXS in the case of isotopically substituted water (HDO and D2O) where the nuclear dynamics is significantly affected by the heavier fragments' mass.
Y1  - 2018
U6  - https://doi.org/10.1039/c8cp01807c
SN  - 1463-9076
SN  - 1463-9084
VL  - 20
IS  - 21
SP  - 14384
EP  - 14397
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Jay, Raphael M.
A1  - Norell, Jesper
A1  - Eckert, Sebastian
A1  - Hantschmann, Markus
A1  - Beye, Martin
A1  - Kennedy, Brian
A1  - Quevedo, Wilson
A1  - Schlotter, William F.
A1  - Dakovski, Georgi L.
A1  - Minitti, Michael P.
A1  - Hoffmann, Matthias C.
A1  - Mitra, Ankush
A1  - Moeller, Stefan P.
A1  - Nordlund, Dennis
A1  - Zhang, Wenkai
A1  - Liang, Huiyang W.
A1  - Kunnus, Kristian
A1  - Kubicek, Katharina
A1  - Techert, Simone A.
A1  - Lundberg, Marcus
A1  - Wernet, Philippe
A1  - Gaffney, Kelly
A1  - Odelius, Michael
A1  - Föhlisch, Alexander
T1  - Disentangling Transient Charge Density and Metal-Ligand Covalency in Photoexcited Ferricyanide with Femtosecond Resonant Inelastic Soft X-ray Scattering
JF  - The journal of physical chemistry letters
N2  - Soft X-ray spectroscopies are ideal probes of the local valence electronic structure of photocatalytically active metal sites. Here, we apply the selectivity of time resolved resonant inelastic X-ray scattering at the iron L-edge to the transient charge distribution of an optically excited charge-transfer state in aqueous ferricyanide. Through comparison to steady-state spectra and quantum chemical calculations, the coupled effects of valence-shell closing and ligand-hole creation are experimentally and theoretically disentangled and described in terms of orbital occupancy, metal-ligand covalency, and ligand field splitting, thereby extending established steady-state concepts to the excited-state domain. pi-Back-donation is found to be mainly determined by the metal site occupation, whereas the ligand hole instead influences sigma-donation. Our results demonstrate how ultrafast resonant inelastic X-ray scattering can help characterize local charge distributions around catalytic metal centers in short-lived charge-transfer excited states, as a step toward future rationalization and tailoring of photocatalytic capabilities of transition-metal complexes.
Y1  - 2018
U6  - https://doi.org/10.1021/acs.jpclett.8b01429
SN  - 1948-7185
VL  - 9
IS  - 12
SP  - 3538
EP  - 3543
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Jay, Raphael Martin
A1  - Eckert, Sebastian
A1  - Fondell, Mattis
A1  - Miedema, Piter S.
A1  - Norell, Jesper
A1  - Pietzsch, Annette
A1  - Quevedo, Wilson
A1  - Niskanen, Johannes
A1  - Kunnus, Kristjan
A1  - Föhlisch, Alexander
T1  - The nature of frontier orbitals under systematic ligand exchange in (pseudo-)octahedral Fe(II) complexes
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - Understanding and controlling properties of transition metal complexes is a crucial step towards tailoring materials for sustainable energy applications. In a systematic approach, we use resonant inelastic X-ray scattering to study the influence of ligand substitution on the valence electronic structure around an aqueous iron(II) center. Exchanging cyanide with 2-2′-bipyridine ligands reshapes frontier orbitals in a way that reduces metal 3d charge delocalization onto the ligands. This net decrease of metal–ligand covalency results in lower metal-centered excited state energies in agreement with previously reported excited state dynamics. Furthermore, traces of solvent-effects were found indicating a varying interaction strength of the solvent with ligands of different character. Our results demonstrate how ligand exchange can be exploited to shape frontier orbitals of transition metal complexes in solution-phase chemistry; insights upon which future efforts can built when tailoring the functionality of photoactive systems for light-harvesting applications.
Y1  - 2018
U6  - https://doi.org/10.1039/c8cp04341h
SN  - 1463-9076
SN  - 1463-9084
VL  - 20
IS  - 44
SP  - 27745
EP  - 27751
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Eckert, Sebastian
A1  - Norell, Jesper
A1  - Jay, Raphael Martin
A1  - Fondell, Mattis
A1  - Mitzner, Rolf
A1  - Odelius, Michael
A1  - Föhlisch, Alexander
T1  - T-1 Population as the Driver of Excited-State Proton-Transfer in 2-Thiopyridone
JF  - Chemistry - a European journal
N2  - Excited-state proton transfer (ESPT) is a fundamental process in biomolecular photochemistry, but its underlying mediators often evade direct observation. We identify a distinct pathway for ESPT in aqueous 2-thiopyridone, by employing transient N1s X-ray absorption spectroscopy and multi-configurational spectrum simulations. Photoexcitations to the singlet S-2 and S-4 states both relax promptly through intersystem crossing to the triplet T-1 state. The T-1 state, through its rapid population and near nanosecond lifetime, mediates nitrogen site deprotonation by ESPT in a secondary intersystem crossing to the S-0 potential energy surface. This conclusively establishes a dominant ESPT pathway for the system in aqueous solution, which is also compatible with previous measurements in acetonitrile. Thereby, the hitherto open questions of the pathway for ESPT in the compound, including its possible dependence on excitation wavelength and choice of solvent, are resolved.
KW  - excited-state proton-transfer
KW  - intersystem crossing
KW  - nitrogen
KW  - photochemistry
KW  - X-ray absorption
Y1  - 2019
U6  - https://doi.org/10.1002/chem.201804166
SN  - 0947-6539
SN  - 1521-3765
VL  - 25
IS  - 7
SP  - 1733
EP  - 1739
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Vaz da Cruz, Vinicius
A1  - Eckert, Sebastian
A1  - Iannuzzi, Marcella
A1  - Ertan, Emelie
A1  - Pietzsch, Annette
A1  - Couto, Rafael C.
A1  - Niskanen, Johannes
A1  - Fondell, Mattis
A1  - Dantz, Marcus
A1  - Schmitt, Thorsten
A1  - Lu, Xingye
A1  - McNally, Daniel
A1  - Jay, Raphael Martin
A1  - Kimberg, Victor
A1  - Föhlisch, Alexander
A1  - Odelius, Michael
T1  - Probing hydrogen bond strength in liquid water by resonant inelastic X-ray scattering
JF  - Nature Communications
N2  - Local probes of the electronic ground state are essential for understanding hydrogen bonding in aqueous environments. When tuned to the dissociative core-excited state at the O1s pre-edge of water, resonant inelastic X-ray scattering back to the electronic ground state exhibits a long vibrational progression due to ultrafast nuclear dynamics. We show how the coherent evolution of the OH bonds around the core-excited oxygen provides access to high vibrational levels in liquid water. The OH bonds stretch into the long-range part of the potential energy curve, which makes the X-ray probe more sensitive than infra-red spectroscopy to the local environment. We exploit this property to effectively probe hydrogen bond strength via the distribution of intramolecular OH potentials derived from measurements. In contrast, the dynamical splitting in the spectral feature of the lowest valence-excited state arises from the short-range part of the OH potential curve and is rather insensitive to hydrogen bonding.
Y1  - 2019
U6  - https://doi.org/10.1038/s41467-019-08979-4
SN  - 2041-1723
VL  - 10
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Niskanen, Johannes
A1  - Fondell, Mattis
A1  - Sahle, Christoph J.
A1  - Eckert, Sebastian
A1  - Jay, Raphael Martin
A1  - Gilmore, Keith
A1  - Pietzsch, Annette
A1  - Dantz, Marcus
A1  - Lu, Xingye
A1  - McNally, Daniel E.
A1  - Schmitt, Thorsten
A1  - Vaz da Cruz, Vinicius
A1  - Kimberg, Victor
A1  - Föhlisch, Alexander
A1  - Gel’mukhanov, Faris
T1  - Compatibility of quantitative X-ray spectroscopy with continuous distribution models of water at ambient conditions
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - The phase diagram of water harbors controversial views on underlying structural properties of its constituting molecular moieties, its fluctuating hydrogen-bonding network, as well as pair-correlation functions. In this work, long energy-range detection of the X-ray absorption allows us to unambiguously calibrate the spectra for water gas, liquid, and ice by the experimental atomic ionization cross-section. In liquid water, we extract the mean value of 1.74 +/- 2.1% donated and accepted hydrogen bonds per molecule, pointing to a continuous-distribution model. In addition, resonant inelastic X-ray scattering with unprecedented energy resolution also supports continuous distribution of molecular neighborhoods within liquid water, as do X-ray emission spectra once the femtosecond scattering duration and proton dynamics in resonant X-ray-matter interaction are taken into account. Thus, X-ray spectra of liquid water in ambient conditions can be understood without a two-structure model, whereas the occurrence of nanoscale-length correlations within the continuous distribution remains open.
KW  - structure of water
KW  - X-ray spectroscopy
KW  - continuous distribution model
Y1  - 2019
U6  - https://doi.org/10.1073/pnas.1815701116
SN  - 0027-8424
VL  - 116
IS  - 10
SP  - 4058
EP  - 4063
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Eckert, Sebastian
A1  - Norell, Jesper
A1  - Miedema, Piter S.
A1  - Beye, Martin
A1  - Fondell, Mattis
A1  - Quevedo, Wilson
A1  - Kennedy, Brian
A1  - Hantschmann, Markus
A1  - Pietzsch, Annette
A1  - van Kuiken, Benjamin
A1  - Ross, Matthew
A1  - Minitti, Michael P.
A1  - Moeller, Stefan P.
A1  - Schlotter, William F.
A1  - Khalil, Munira
A1  - Odelius, Michael
A1  - Föhlisch, Alexander
T1  - Untersuchung unabhängiger N‐H‐ und N‐C‐Bindungsverformungen auf ultrakurzen Zeitskalen mit resonanter inelastischer Röntgenstreuung
JF  - Angewandte Chemie
N2  - Die Femtosekundendynamik nach resonanten Photoanregungen mit optischen und Röntgenpulsen ermöglicht eine selektive Verformung von chemischen N‐H‐ und N‐C‐Bindungen in 2‐Thiopyridon in wässriger Lösung. Die Untersuchung der orbitalspezifischen elektronischen Struktur und ihrer Dynamik auf ultrakurzen Zeitskalen mit resonanter inelastischer Röntgenstreuung an der N1s‐Resonanz am Synchrotron und dem Freie‐Elektronen‐Laser LCLS in Kombination mit quantenchemischen Multikonfigurationsberechnungen erbringen den direkten Nachweis dieser kontrollierten photoinduzierten Molekülverformungen und ihrer ultrakurzen Zeitskala.
KW  - Photochemie
KW  - Protonierung
KW  - RIXS (resonante inelastische Röntgenstreuung)
KW  - Selektiver Bindungsbruch
KW  - Stickstoff
Y1  - 2017
U6  - https://doi.org/10.1002/ange.201700239
SN  - 1521-3757
SN  - 1521-3773
VL  - 129
IS  - 22
SP  - 6184
EP  - 6188
ER  - 
TY  - JOUR
A1  - Vaz da Cruz, Vinícius
A1  - Ignatova, Nina
A1  - Couto, Rafael
A1  - Fedotov, Daniil
A1  - Rehn, Dirk R.
A1  - Savchenko, Viktoriia
A1  - Norman, Patrick
A1  - Ågren, Hans
A1  - Polyutov, Sergey
A1  - Niskanen, Johannes
A1  - Eckert, Sebastian
A1  - Jay, Raphael Martin
A1  - Fondell, Mattis
A1  - Schmitt, Thorsten
A1  - Pietzsch, Annette
A1  - Föhlisch, Alexander
A1  - Odelius, Michael
A1  - Kimberg, Victor
A1  - Gel’mukhanov, Faris
T1  - Nuclear dynamics in resonant inelastic X-ray scattering and X-ray absorption of methanol
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - We report on a combined theoretical and experimental study of core-excitation spectra of gas and liquid phase methanol as obtained with the use of X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). The electronic transitions are studied with computational methods that include strict and extended second-order algebraic diagrammatic construction [ADC(2) and ADC(2)-x], restricted active space second-order perturbation theory, and time-dependent density functional theory-providing a complete assignment of the near oxygen K-edge XAS. We show that multimode nuclear dynamics is of crucial importance for explaining the available experimental XAS and RIXS spectra. The multimode nuclear motion was considered in a recently developed "mixed representation" where dissociative states and highly excited vibrational modes are accurately treated with a time-dependent wave packet technique, while the remaining active vibrational modes are described using Franck-Condon amplitudes. Particular attention is paid to the polarization dependence of RIXS and the effects of the isotopic substitution on the RIXS profile in the case of dissociative core-excited states. Our approach predicts the splitting of the 2a RIXS peak to be due to an interplay between molecular and pseudo-atomic features arising in the course of transitions between dissociative core- and valence-excited states. The dynamical nature of the splitting of the 2a peak in RIXS of liquid methanol near pre-edge core excitation is shown. The theoretical results are in good agreement with our liquid phase measurements and gas phase experimental data available from the literature. (C) 2019 Author(s).
Y1  - 2019
U6  - https://doi.org/10.1063/1.5092174
SN  - 0021-9606
SN  - 1089-7690
VL  - 150
IS  - 23
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Jay, Raphael Martin
A1  - Eckert, Sebastian
A1  - Vaz da Cruz, Vinicius
A1  - Fondell, Mattis
A1  - Mitzner, Rolf
A1  - Föhlisch, Alexander
T1  - Covalency-driven preservation of local charge densities in a metal-to-ligand charge-transfer excited iron photosensitizer
JF  - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition
N2  - Charge-density rearrangements after metal-to-ligand charge-transfer excitation in an iron photosensitizer are investigated by R. M Jay, A. Fohlisch et al. in their Communication (DOI: 10.1002/anie.201904761). By using time-resolved X-ray absorption spectroscopy, surprising covalency-effects are revealed that inhibit charge-separation at the intra-molecular level. Furthermore, the underlying mechanism is proposed to be generally in effect for all commonly used photosensitizers in light-harvesting applications, which challenges the common perception of electronic charge-transfer.
KW  - charge-transfer
KW  - density functional calculations
KW  - iron
KW  - photochemistry
KW  - X-ray absorption spectroscopy
Y1  - 2019
U6  - https://doi.org/10.1002/anie.201904761
SN  - 1433-7851
SN  - 1521-3773
VL  - 58
IS  - 31
SP  - 10742
EP  - 10746
PB  - Wiley-VCH
CY  - Weinheim
ER  -