@article{11d4f3755188400aba2a63fec7334ede,
title = "Isomer-specific photofragmentation of C3H3+ at the carbon K-edge",
abstract = "Individual fingerprints of different isomers of C3H3+ cations have been identified by studying photoionization, photoexcitation, and photofragmentation of C3H3+ near the carbon K-edge. The experiment was performed employing the photon-ion merged-beams technique at the photon-ion spectrometer at PETRA III (PIPE). This technique is a variant of near-edge X-ray absorption fine-structure spectroscopy, which is particularly sensitive to the 1s → π* excitation. The C3H3+ primary ions were generated by an electron cyclotron resonance ion source. C3Hn2+ product ions with n = 0, 1, 2, and 3 were observed for photon energies in the range of 279.0 eV to 295.2 eV. The experimental spectra are interpreted with the aid of theoretical calculations within the framework of time-dependent density functional theory. To this end, absorption spectra have been calculated for three different constitutional isomers of C3H3+. We find that our experimental approach offers a new possibility to study at the same time details of the electronic structure and of the geometry of molecular ions such as C3H3+",
author = "Simon Reinwardt and Patrick Cieslik and Ticia Buhr and Alexander Perry-Sassmannshausen and Stefan Schippers and Alfred M{\"u}ller and Florian Trinter and Michael Martins",
year = "2024",
month = jan,
day = "1",
doi = "10.1039/d4cp00370e",
language = "English",
volume = "26",
pages = "15519--15529",
journal = "Physical Chemistry Chemical Physics",
issn = "1463-9076",
publisher = "Royal Society of Chemistry",
number = "21",
}
@article{612fac9c05e64a3e899937ef1c41ada6,
title = "Isotope effects in dynamics of water isotopologues induced by core ionization at an x-ray free-electron laser",
abstract = "Dynamical response of water exposed to x-rays is of utmost importance in a wealth of science areas. We exposed isolated water isotopologues to short x-ray pulses from a free-electron laser and detected momenta of all produced ions in coincidence. By combining experimental results and theoretical modeling, we identify significant structural dynamics with characteristic isotope effects in H2O2+, D2O2+, and HDO2+, such as asymmetric bond elongation and bond-angle opening, leading to two-body or three-body fragmentation on a timescale of a few femtoseconds. A method to disentangle the sequences of events taking place upon the consecutive absorption of two x-ray photons is described. The obtained deep look into structural properties and dynamics of dissociating water isotopologues provides essential insights into the underlying mechanisms.",
author = "R. Guillemin and L. Inhester and M. Ilchen and T. Mazza and R. Boll and Th Weber and S. Eckart and P. Grychtol and N. Rennhack and T. Marchenko and N. Velasquez and O. Travnikova and I. Ismail and J. Niskanen and E. Kukk and F. Trinter and M. Gisselbrecht and R. Feifel and G. Sansone and D. Rolles and M. Martins and M. Meyer and M. Simon and R. Santra and T. Pfeifer and T. Jahnke and Piancastelli, \{M. N.\}",
note = "Publisher Copyright: {\textcopyright} 2023 Author(s).",
year = "2023",
month = sep,
day = "1",
doi = "10.1063/4.0000197",
language = "English",
volume = "10",
journal = "Structural dynamics ",
issn = "2329-7778",
publisher = "AIP Publishing",
number = "5",
}
@article{2261b30d16d5488cb1fdf8199b8de0ea,
title = "Soft X-Ray-induced Dimerization of Methane",
abstract = "Carbon 1s excitation of methane, CH4, has been studied in the gas phase using the ion trap integrated with the photon–ion instrument at PETRA III/DESY and soft X-rays from the beamline P04. The created photoions are stored within the ion trap so that in further steps the photoions can undergo reactions with neutral methane molecules. The ionic photoproducts as well as reaction products created thereby are mass-over-charge analyzed by an ion time-of-flight spectrometer. Besides the photoions, product ions with up to three carbon atoms are found. In contrast to experiments using vacuum ultraviolet radiation, especially highly reactive product ions with a small number of hydrogen atoms such as C2H2+ and C2H3+ are found, which are important precursors for larger hydrocarbons such as C6H6. Possible production routes of the product ions are analyzed on the basis of a model that considers the probabilities for photofragmentation and the first subsequent chemical reaction step. The model indicates that the high degree of fragmentation by photons with energies around 280 eV is favoring these products. The results of the measurements show that the products like C2H2+ and C2H3+ can be generated by a single collision of the ionization product with neutral methane. The results suggest that soft X-rays might be important for chemical reactions in planetary atmospheres, which has usually not been taken into account. However, due to the high degree of fragmentation and large cross sections involved, they can have a large influence even when the corresponding photon flux is rather small.",
author = "S Reinwardt and Ivan Baev and Patrick Cieslik and Karolin Baev and Ticia Buhr and Alexander Perry-Sassmannshausen and Stefan Schippers and Alfred M{\"u}ller and Florian Trinter and Jens Viefhaus and Michael Martins",
year = "2023",
month = jul,
day = "1",
doi = "10.3847/1538-4357/acd937",
language = "English",
volume = "952",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "American Astronomical Society",
number = "1",
}
@article{e42d07381c8a4eceb1fdb67cab21f7f3,
title = "Electronic quantum coherence in glycine molecules probed with ultrashort x-ray pulses in real time",
abstract = "Here, we use x-rays to create and probe quantum coherence in the photoionized amino acid glycine. The outgoing photoelectron leaves behind the cation in a coherent superposition of quantum mechanical eigenstates. Delayed x-ray pulses track the induced coherence through resonant x-ray absorption that induces Auger decay and by photoelectron emission from sequential double photoionization. Sinusoidal temporal modulation of the detected signal at early times (0 to 25 fs) is observed in both measurements. Advanced ab initio many-electron simulations allow us to explain the first 25 fs of the detected coherent quantum evolution in terms of the electronic coherence. In the kinematically complete x-ray absorption measurement, we monitor its dynamics for a period of 175 fs and observe an evolving modulation that may implicate the coupling of electronic to vibronic coherence at longer time scales. Our experiment provides a direct support for the existence of long-lived electronic coherence in photoionized biomolecules.",
author = "David Schwickert and Marco Ruberti and P{\v r}emysl Koloren{\v c} and Sergey Usenko and Andreas Przystawik and Karolin Baev and Ivan Baev and Markus Braune and Lars Bocklage and Czwalinna, \{Marie Kristin\} and Sascha Deinert and Stefan D{\"u}sterer and Andreas Hans and Gregor Hartmann and Christian Haunhorst and Marion Kuhlmann and Steffen Palutke and Ralf R{\"o}hlsberger and Juliane R{\"o}nsch-Schulenburg and Philipp Schmidt and Sven Toleikis and Jens Viefhaus and Michael Martins and Andr{\'e} Knie and Detlef Kip and Vitali Averbukh and Marangos, \{Jon P.\} and Tim Laarmann",
year = "2022",
month = jun,
day = "3",
doi = "10.1126/sciadv.abn6848",
language = "English",
volume = "8",
journal = "Science Advances ",
issn = "2375-2548",
publisher = "American Association for the Advancement of Science",
number = "22",
}
@article{29c15b23e16144f39dddcd5c358112ec,
title = "Inner-Shell-Ionization-Induced Femtosecond Structural Dynamics of Water Molecules Imaged at an X-Ray Free-Electron Laser",
abstract = "The ultrafast structural dynamics of water following inner-shell ionization is a crucial issue in high-energy radiation chemistry. We have exposed isolated water molecules to a short X-ray pulse from a free-electron laser and detected momenta of all produced ions in coincidence. By combining experimental results and theoretical modeling, we can image dissociation dynamics of individual molecules in unprecedented detail. We reveal significant molecular structural dynamics in H2O2+, such as asymmetric deformation and bond-angle opening, leading to two-body or three-body fragmentation on a timescale of a few femtoseconds. We thus reconstruct several snapshots of structural dynamics at different time intervals, which highlight dynamical patterns that are relevant as initiating steps of subsequent radiation-damage processes.",
author = "T. Jahnke and R. Guillemin and L. Inhester and Son, \{S. K.\} and G. Kastirke and M. Ilchen and J. Rist and D. Trabert and N. Melzer and N. Anders and T. Mazza and R. Boll and \{De Fanis\}, A. and V. Music and Th Weber and M. Weller and S. Eckart and K. Fehre and S. Grundmann and A. Hartung and M. Hofmann and C. Janke and M. Kircher and G. Nalin and A. Pier and J. Siebert and N. Strenger and I. Vela-Perez and Baumann, \{T. M.\} and P. Grychtol and J. Montano and Y. Ovcharenko and N. Rennhack and Rivas, \{D. E.\} and R. Wagner and P. Ziolkowski and P. Schmidt and T. Marchenko and O. Travnikova and L. Journel and I. Ismail and E. Kukk and J. Niskanen and F. Trinter and C. Vozzi and M. Devetta and S. Stagira and M. Gisselbrecht and J{\"a}ger, \{A. L.\} and X. Li and Y. Malakar and M. Martins and R. Feifel and Schmidt, \{L. Ph H.\} and A. Czasch and G. Sansone and D. Rolles and A. Rudenko and R. Moshammer and R. D{\"o}rner and M. Meyer and T. Pfeifer and Sch{\"o}ffler, \{M. S.\} and R. Santra and M. Simon and Piancastelli, \{M. N.\}",
year = "2021",
month = dec,
day = "3",
doi = "10.1103/PhysRevX.11.041044",
language = "English",
volume = "11",
pages = "041044",
journal = "Physical review X",
issn = "2160-3308",
publisher = "American Physical Society (APS)",
number = "4",
}
@article{60442b17280846d3b66238a0ad732e1e,
title = "Multiple photodetachment of silicon anions via K -shell excitation and ionization",
abstract = "Experimental cross sections for m-fold photodetachment (m=3–6) of silicon anions via K-shell excitation and ionization were measured in the photon-energy range of 1830–1900 eV using the photon-ion merged-beams technique at a synchrotron light source. All cross sections exhibit a threshold behavior that is masked by prethreshold resonances associated with the excitation of a 1s electron to higher, either partly occupied or unoccupied atomic subshells. Results from multiconfiguration Dirac-Fock calculations agree with the experimentally derived cross sections for photoabsorption if small energy shifts are applied to the calculated resonance positions and detachment thresholds. Moreover, a systematic approach is applied for modeling the deexcitation cascades that set in after the initial creation of a K-shell hole. The resulting product charge-state distributions compare well with the measured ones for direct K-shell detachment but less well for resonant K-shell excitation. The present results are potentially useful for identifying silicon anions in cold plasmas such as interstellar gas clouds.",
author = "A. Perry-Sassmannshausen and T. Buhr and M. Martins and S. Reinwardt and F. Trinter and A. M{\"u}ller and S. Fritzsche and S. Schippers",
year = "2021",
month = nov,
day = "15",
doi = "10.1103/PhysRevA.104.053107",
language = "English",
volume = "104",
journal = "Physical Review A",
issn = "1050-2947",
publisher = "American Physical Society",
number = "5",
}
@article{d7f32f61e8174437b36b12b282de7e34,
title = "Role of L -shell single and double core-hole production and decay in m -fold ( 1≤m≤6 ) photoionization of the Ar+ ion",
abstract = "Multiple ionization of the Ar+(3s23p5) ion by a single photon has been investigated in the photon-energy range 250-1800 eV employing the photon-ion merged-beams technique. Absolute partial cross sections were measured for all Ar(1+m)+ product-ion channels with 1≤m≤6 covering a size range from several tens of Mb down to a few b. Narrow 2p-subshell excitation resonances were observed in all channels up to quadruple ionization at a photon-energy bandwidth of 52 meV. Double excitations involving a 2p and a 3s or 3p electron were also studied at high resolution and the measurements of the broad 2s excitation resonances directly showed their natural widths. Contributions of direct photo double ionization (PDI) to the production of the highest final Ar ion charge states are revealed, with PDI of the 2s subshell being mainly responsible for the production of Ar7+. The experiment made use of the PIPE setup installed at beamline P04 of the PETRA III synchrotron light source of DESY in Hamburg. The measurements were supported by theoretical calculations to identify the main contributions to the observed cross sections. Comparisons of theory and experiment show remarkable agreement but also hint to additional ionization mechanisms that are not considered in the theoretical models such as core ionization accompanied by excitations with subsequent Auger decays leading to net m-fold ionization with m≥4.",
author = "A. M{\"u}ller and M. Martins and A. Borovik and T. Buhr and A. Perry-Sassmannshausen and S. Reinwardt and F. Trinter and S. Schippers and S. Fritzsche and Kheifets, \{A. S.\}",
year = "2021",
month = sep,
day = "9",
doi = "10.1103/PhysRevA.104.033105",
language = "English",
volume = "104",
journal = "Physical Review A",
issn = "1050-2947",
publisher = "American Physical Society",
number = "3",
}
@article{7095515e31f1417bad854146dbf81751,
title = "Surface characterization and resistance changes of silver-nanowire networks upon atmospheric plasma treatment",
abstract = "Highly conductive silver-nanowire (Ag-NW) networks are used in composite materials as conductive channels. Their resistance tuning can be accomplished by changing the Ag-NW concentration, and, therefore, changing the network structure. In this study, an alternative pathway to resistance engineering of conductive Ag-NW networks by local atmospheric plasma treatment is employed. The corresponding changes in nanowire network morphology and crystallinity as a function of plasma etching time are investigated by time-resolved grazing-incidence X-ray scattering, field-effect scanning electron microscopy, and X-ray photoelectron spectroscopy. Three characteristic etching phases are identified. The first two phases enable the controlled engineering of the electrical properties with different rates of resistance change, which results from changes in nanowire shape, network morphology, and different oxidation rates. Phase III is characterized by pronounced fragmentation and destruction of the Ag-NW networks. These results show the feasibility of atmospheric plasma treatments to tune the local electrical properties of conductive Ag-NW networks. Furthermore, we present a physical Monte Carlo model explaining the electrical network properties as a function of plasma etching time based on the network connectivity and a constant plasma etching rate of 570 ng s−1 cm−2.",
keywords = "Atmospheric plasma treatment, Crystallinity, In situ X-ray scattering, Monte Carlo simulation, Resistance, Silver nanowire networks",
author = "Akinsinde, \{Lewis O.\} and Glier, \{Tomke E.\} and Matthias Schwartzkopf and Marie Betker and Matz Nissen and Maximilian Witte and Sarah Scheitz and Christian Nweze and Benjamin Grimm-Lebsanft and Marc Gensch and Andrei Chumakov and Ivan Baev and Ulrich Sch{\"u}rmann and Torben Dankwort and Frank Fischer and Michael Martins and Roth, \{Stephan V.\} and Lorenz Kienle and Michael R{\"u}bhausen",
year = "2021",
month = jun,
day = "1",
doi = "10.1016/j.apsusc.2021.149362",
language = "English",
volume = "550",
journal = "Applied surface science",
issn = "0169-4332",
publisher = "Elsevier BV",
}
@article{48f67ebef9ee4638bc4af49fc61a0039,
title = "Evidence for Conical Magnetic Structure in M-Type BaFe12O19 Hexaferrite: A Combined Single-Crystal X-ray Magnetic Circular Dichroism and Neutron Diffraction Study",
abstract = "The magnetic ground state of BaFe12O19 (BFO) is investigated using X-ray absorption spectra (XAS), X-ray magnetic circular dichroism (XMCD), and neutron diffraction studies at 1.2 and 1.5 K, respectively. The XMCD measurements on single-crystals of BFO in grazing-incidence geometry reveal canting of the spins away from the c-axis of the hexagonal unit cell. Single-crystal neutron diffraction studies reveal magnetic satellite peaks along the 00l reciprocal lattice row around the forbidden l = 2n ± 1 positions confirming the conical-type magnetic structure in the ground state of BFO. The observation of the conical magnetic structure of BFO opens the possibility of type-II multiferroicity in undoped BFO.",
keywords = "BaFe12O19, noncollinear magnetic structures, single-crystal neutron diffraction, X-ray absorption spectra, X-ray magnetic circular dichroism",
author = "Keshav Kumar and Mishra, \{Shrawan Kumar\} and Sanjay Singh and Ivan Baev and Michael Martins and Fabio Orlandi and Pascal Manuel and Dhananjai Pandey",
year = "2021",
month = mar,
day = "8",
doi = "10.1002/pssr.202000506",
language = "English",
pages = "2000506",
journal = "Physica Status Solidi - Rapid Research Letters",
issn = "1862-6254",
publisher = "Wiley-VCH Verlag",
}
@article{238721fa78bb4ac8939ffa969fe0cb07,
title = "Disentangling the Photodissociation Dynamics of the HF+ Molecular Radical via Kinetic-Energy-Release-Resolved F 1s Core Excitation and Ionization",
abstract = "The F 1s core level photoionization of the ionic molecular radical HF+ has been studied using the photon-ion merged-beams technique at a synchrotron radiation source. Upon analyzing kinetic energy release (KER) dependent photoion yield spectra, complex ultrafast dissociation dynamics of the F 1s core hole excited σ∗ state can be revealed. By means of configuration-interaction electronic structure calculations of the excited molecular potential energy curves, this complex process can be attributed to a spin-dependent dissociation of the excited σ∗ biradical state.",
author = "M. Martins and S. Reinwardt and Schunck, \{J. O.\} and J. Schwarz and K. Baev and A. M{\"u}ller and T. Buhr and A. Perry-Sassmannshausen and S. Klumpp and S. Schippers",
year = "2021",
month = feb,
day = "11",
doi = "10.1021/acs.jpclett.0c03356",
language = "English",
volume = "12",
pages = "1390--1395",
journal = "The journal of physical chemistry letters",
issn = "1948-7185",
publisher = "American Chemical Society",
number = "5",
}