@article{EckertVazdaCruzOchmannetal.2021,
  author    = {Eckert, Sebastian and Vaz da Cruz, Vin{\´i}cius and Ochmann, Miguel and Ahnen, Inga von and F{\"o}hlisch, Alexander and Huse, Nils},
  title     = {Breaking the symmetry of pyrimidine},
  series = {The journal of physical chemistry letters},
  volume    = {12},
  journal   = {The journal of physical chemistry letters},
  number    = {35},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1948-7185},
  doi       = {10.1021/acs.jpclett.1c01865},
  pages     = {8637 -- 8643},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}
@article{OchmannVazdaCruzEckertetal.2022,
  author    = {Ochmann, Miguel and Vaz da Cruz, Vinicius and Eckert, Sebastian and Huse, Nils and F{\"o}hlisch, Alexander},
  title     = {R-Group stabilization in methylated formamides observed by resonant inelastic X-ray scattering},
  series = {Chemical communications: ChemComm},
  volume    = {58},
  journal   = {Chemical communications: ChemComm},
  number    = {63},
  publisher = {The Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1359-7345},
  doi       = {10.1039/d2cc00053a},
  pages     = {8834 -- 8837},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{JayEckertMitzneretal.2020,
  author    = {Jay, Raphael M. and Eckert, Sebastian and Mitzner, Rolf and Fondell, Mattis and F{\"o}hlisch, Alexander},
  title     = {Quantitative evaluation of transient valence orbital occupations in a 3d transition metal complex as seen from the metal and ligand perspective},
  series = {Chemical physics letters},
  volume    = {754},
  journal   = {Chemical physics letters},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0009-2614},
  doi       = {10.1016/j.cplett.2020.137681},
  pages     = {5},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{VazdaCruzEckertFoehlisch2021,
  author    = {Vaz da Cruz, Vin{\´i}cius and Eckert, Sebastian and F{\"o}hlisch, Alexander},
  title     = {TD-DFT simulations of K-edge resonant inelastic X-ray scattering within the restricted subspace approximation},
  series = {Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies},
  volume    = {23},
  journal   = {Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies},
  number    = {3},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/d0cp04726k},
  pages     = {1835 -- 1848},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}
@article{EckertMascarenhasMitzneretal.2022,
  author    = {Eckert, Sebastian and Mascarenhas, Eric Johnn and Mitzner, Rolf and Jay, Raphael Martin and Pietzsch, Annette and Fondell, Mattis and Vaz da Cruz, Vinicius and F{\"o}hlisch, Alexander},
  title     = {From the free ligand to the transition metal complex},
  series = {Inorganic chemistry},
  volume    = {61},
  journal   = {Inorganic chemistry},
  number    = {27},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0020-1669},
  doi       = {10.1021/acs.inorgchem.2c00789},
  pages     = {10321 -- 10328},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{VazdaCruzBuechnerFondelletal.2022,
  author    = {Vaz da Cruz, Vinicius and B{\"u}chner, Robby and Fondell, Mattis and Pietzsch, Annette and Eckert, Sebastian and F{\"o}hlisch, Alexander},
  title     = {Targeting individual tautomers in equilibrium by resonant inelastic X-ray scattering},
  series = {The journal of physical chemistry letters},
  volume    = {13},
  journal   = {The journal of physical chemistry letters},
  number    = {10},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1948-7185},
  doi       = {10.1021/acs.jpclett.1c03453},
  pages     = {2459 -- 2466},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{MascarenhasFondellBuechneretal.2022,
  author    = {Mascarenhas, Eric Johnn and Fondell, Mattis and B{\"u}chner, Robby and Eckert, Sebastian and Vaz da Cruz, Vin{\´i}cius and F{\"o}hlisch, Alexander},
  title     = {Photo-induced ligand substitution of Cr(CO)(6) in 1-pentanol probed by time resolved X-ray absorption spectroscopy},
  series = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  volume    = {24},
  journal   = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  number    = {30},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/d1cp05834g},
  pages     = {17979 -- 17985},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{PietzschNiskanenVazdaCruzetal.2022,
  author    = {Pietzsch, Annette and Niskanen, Johannes and Vaz da Cruz, Vinicius and B{\"u}chner, Robby and Eckert, Sebastian and Fondell, Mattis and Jay, Raphael Martin and Lu, Xingye and McNally, Daniel and Schmitt, Thorsten and F{\"o}hlisch, Alexander},
  title     = {Cuts through the manifold of molecular H2O potential energy surfaces in liquid water at ambient conditions},
  series = {Proceedings of the National Academy of Sciences of the United States of America},
  volume    = {119},
  journal   = {Proceedings of the National Academy of Sciences of the United States of America},
  number    = {28},
  publisher = {National Acad. of Sciences},
  address   = {Washington, DC},
  issn      = {1091-6490},
  doi       = {10.1073/pnas.2118101119},
  pages     = {6},
  year      = {2022},
  abstract  = {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.},
  language  = {en}
}
@article{JayVazdaCruzEckertetal.2020,
  author    = {Jay, Raphael M. and Vaz da Cruz, Vinicius and Eckert, Sebastian and Fondell, Mattis and Mitzner, Rolf and F{\"o}hlisch, Alexander},
  title     = {Probing solute-solvent interactions of transition metal complexes using L-edge absorption spectroscopy},
  series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry},
  volume    = {124},
  journal   = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry},
  number    = {27},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1520-6106},
  doi       = {10.1021/acs.jpcb.0c00638},
  pages     = {5636 -- 5645},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{CoutoCruzErtanetal.2017,
  author    = {Couto, Rafael C. and Cruz, Vinicius V. and Ertan, Emelie and Eckert, Sebastian and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and Guimaraes, Freddy F. and Agren, Hans and Odelius, Michael and Kimberg, Victor and F{\"o}hlisch, Alexander},
  title     = {Selective gating to vibrational modes through resonant X-ray scattering},
  series = {Nature Communications},
  volume    = {8},
  journal   = {Nature Communications},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2041-1723},
  doi       = {10.1038/ncomms14165},
  pages     = {7},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{EckertVazdaCruzErtanetal.2018,
  author    = {Eckert, Sebastian and Vaz da Cruz, Vinicius and Ertan, Emelie and Ignatova, Nina and Polyutov, Sergey and Couto, Rafael C. and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and Odelius, Michael and F{\"o}hlisch, Alexander},
  title     = {One-dimensional cuts through multidimensional potential-energy surfaces by tunable x rays},
  series = {Physical review : A, Atomic, molecular, and optical physics},
  volume    = {97},
  journal   = {Physical review : A, Atomic, molecular, and optical physics},
  number    = {5},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2469-9926},
  doi       = {10.1103/PhysRevA.97.053410},
  pages     = {7},
  year      = {2018},
  abstract  = {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.},
  language  = {en}
}
@article{ErtanSavchenkoIgnatovaetal.2018,
  author    = {Ertan, Emelie and Savchenko, Viktoriia and Ignatova, Nina and Vaz da Cruz, Vinicius and Couto, Rafael C. and Eckert, Sebastian and Fondell, Mattis and Dantz, Marcus and Kennedy, Brian and Schmitt, Thorsten and Pietzsch, Annette and F{\"o}hlisch, Alexander and Odelius, Michael and Kimberg, Victor},
  title     = {Ultrafast dissociation features in RIXS spectra of the water molecule},
  series = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  volume    = {20},
  journal   = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  number    = {21},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/c8cp01807c},
  pages     = {14384 -- 14397},
  year      = {2018},
  abstract  = {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.},
  language  = {en}
}
@article{JayNorellEckertetal.2018,
  author    = {Jay, Raphael M. and Norell, Jesper and Eckert, Sebastian and Hantschmann, Markus and Beye, Martin and Kennedy, Brian and Quevedo, Wilson and Schlotter, William F. and Dakovski, Georgi L. and Minitti, Michael P. and Hoffmann, Matthias C. and Mitra, Ankush and Moeller, Stefan P. and Nordlund, Dennis and Zhang, Wenkai and Liang, Huiyang W. and Kunnus, Kristian and Kubicek, Katharina and Techert, Simone A. and Lundberg, Marcus and Wernet, Philippe and Gaffney, Kelly and Odelius, Michael and F{\"o}hlisch, Alexander},
  title     = {Disentangling Transient Charge Density and Metal-Ligand Covalency in Photoexcited Ferricyanide with Femtosecond Resonant Inelastic Soft X-ray Scattering},
  series = {The journal of physical chemistry letters},
  volume    = {9},
  journal   = {The journal of physical chemistry letters},
  number    = {12},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1948-7185},
  doi       = {10.1021/acs.jpclett.8b01429},
  pages     = {3538 -- 3543},
  year      = {2018},
  abstract  = {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.},
  language  = {en}
}
@article{JayEckertFondelletal.2018,
  author    = {Jay, Raphael Martin and Eckert, Sebastian and Fondell, Mattis and Miedema, Piter S. and Norell, Jesper and Pietzsch, Annette and Quevedo, Wilson and Niskanen, Johannes and Kunnus, Kristjan and F{\"o}hlisch, Alexander},
  title     = {The nature of frontier orbitals under systematic ligand exchange in (pseudo-)octahedral Fe(II) complexes},
  series = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  volume    = {20},
  journal   = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  number    = {44},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/c8cp04341h},
  pages     = {27745 -- 27751},
  year      = {2018},
  abstract  = {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.},
  language  = {en}
}
@article{EckertNorellJayetal.2019,
  author    = {Eckert, Sebastian and Norell, Jesper and Jay, Raphael Martin and Fondell, Mattis and Mitzner, Rolf and Odelius, Michael and F{\"o}hlisch, Alexander},
  title     = {T-1 Population as the Driver of Excited-State Proton-Transfer in 2-Thiopyridone},
  series = {Chemistry - a European journal},
  volume    = {25},
  journal   = {Chemistry - a European journal},
  number    = {7},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0947-6539},
  doi       = {10.1002/chem.201804166},
  pages     = {1733 -- 1739},
  year      = {2019},
  abstract  = {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.},
  language  = {en}
}
@article{VazdaCruzEckertIannuzzietal.2019,
  author    = {Vaz da Cruz, Vinicius and Eckert, Sebastian and Iannuzzi, Marcella and Ertan, Emelie and Pietzsch, Annette and Couto, Rafael C. and Niskanen, Johannes and Fondell, Mattis and Dantz, Marcus and Schmitt, Thorsten and Lu, Xingye and McNally, Daniel and Jay, Raphael Martin and Kimberg, Victor and F{\"o}hlisch, Alexander and Odelius, Michael},
  title     = {Probing hydrogen bond strength in liquid water by resonant inelastic X-ray scattering},
  series = {Nature Communications},
  volume    = {10},
  journal   = {Nature Communications},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2041-1723},
  doi       = {10.1038/s41467-019-08979-4},
  pages     = {9},
  year      = {2019},
  abstract  = {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.},
  language  = {en}
}
@article{NiskanenFondellSahleetal.2019,
  author    = {Niskanen, Johannes and Fondell, Mattis and Sahle, Christoph J. and Eckert, Sebastian and Jay, Raphael Martin and Gilmore, Keith and Pietzsch, Annette and Dantz, Marcus and Lu, Xingye and McNally, Daniel E. and Schmitt, Thorsten and Vaz da Cruz, Vinicius and Kimberg, Victor and F{\"o}hlisch, Alexander and Gel'mukhanov, Faris},
  title     = {Compatibility of quantitative X-ray spectroscopy with continuous distribution models of water at ambient conditions},
  series = {Proceedings of the National Academy of Sciences of the United States of America},
  volume    = {116},
  journal   = {Proceedings of the National Academy of Sciences of the United States of America},
  number    = {10},
  publisher = {National Acad. of Sciences},
  address   = {Washington},
  issn      = {0027-8424},
  doi       = {10.1073/pnas.1815701116},
  pages     = {4058 -- 4063},
  year      = {2019},
  abstract  = {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.},
  language  = {en}
}
@article{EckertNorellMiedemaetal.2017,
  author    = {Eckert, Sebastian and Norell, Jesper and Miedema, Piter S. and Beye, Martin and Fondell, Mattis and Quevedo, Wilson and Kennedy, Brian and Hantschmann, Markus and Pietzsch, Annette and van Kuiken, Benjamin and Ross, Matthew and Minitti, Michael P. and Moeller, Stefan P. and Schlotter, William F. and Khalil, Munira and Odelius, Michael and F{\"o}hlisch, Alexander},
  title     = {Untersuchung unabh{\"a}ngiger N-H- und N-C-Bindungsverformungen auf ultrakurzen Zeitskalen mit resonanter inelastischer R{\"o}ntgenstreuung},
  series = {Angewandte Chemie},
  volume    = {129},
  journal   = {Angewandte Chemie},
  number    = {22},
  issn      = {1521-3757},
  doi       = {10.1002/ange.201700239},
  pages     = {6184 -- 6188},
  year      = {2017},
  abstract  = {Die Femtosekundendynamik nach resonanten Photoanregungen mit optischen und R{\"o}ntgenpulsen erm{\"o}glicht eine selektive Verformung von chemischen N-H- und N-C-Bindungen in 2-Thiopyridon in w{\"a}ssriger L{\"o}sung. Die Untersuchung der orbitalspezifischen elektronischen Struktur und ihrer Dynamik auf ultrakurzen Zeitskalen mit resonanter inelastischer R{\"o}ntgenstreuung an der N1s-Resonanz am Synchrotron und dem Freie-Elektronen-Laser LCLS in Kombination mit quantenchemischen Multikonfigurationsberechnungen erbringen den direkten Nachweis dieser kontrollierten photoinduzierten Molek{\"u}lverformungen und ihrer ultrakurzen Zeitskala.},
  language  = {de}
}
@article{VazdaCruzIgnatovaCoutoetal.2019,
  author    = {Vaz da Cruz, Vin{\´i}cius and Ignatova, Nina and Couto, Rafael and Fedotov, Daniil and Rehn, Dirk R. and Savchenko, Viktoriia and Norman, Patrick and {\AA}gren, Hans and Polyutov, Sergey and Niskanen, Johannes and Eckert, Sebastian and Jay, Raphael Martin and Fondell, Mattis and Schmitt, Thorsten and Pietzsch, Annette and F{\"o}hlisch, Alexander and Odelius, Michael and Kimberg, Victor and Gel'mukhanov, Faris},
  title     = {Nuclear dynamics in resonant inelastic X-ray scattering and X-ray absorption of methanol},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {150},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {23},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.5092174},
  pages     = {20},
  year      = {2019},
  abstract  = {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).},
  language  = {en}
}
@article{JayEckertVazdaCruzetal.2019,
  author    = {Jay, Raphael Martin and Eckert, Sebastian and Vaz da Cruz, Vinicius and Fondell, Mattis and Mitzner, Rolf and F{\"o}hlisch, Alexander},
  title     = {Covalency-driven preservation of local charge densities in a metal-to-ligand charge-transfer excited iron photosensitizer},
  series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition},
  volume    = {58},
  journal   = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition},
  number    = {31},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1433-7851},
  doi       = {10.1002/anie.201904761},
  pages     = {10742 -- 10746},
  year      = {2019},
  abstract  = {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.},
  language  = {en}
}