@article{deJongKukrejaTrabantetal.2013, author = {de Jong, S. and Kukreja, R. and Trabant, C. and Pontius, N. and Chang, C. F. and Kachel, T. and Beye, Martin and Sorgenfrei, Nomi and Back, C. H. and Braeuer, B. and Schlotter, W. F. and Turner, J. J. and Krupin, O. and Doehler, M. and Zhu, D. and Hossain, M. A. and Scherz, A. O. and Fausti, D. and Novelli, F. and Esposito, M. and Lee, W. S. and Chuang, Y. D. and Lu, D. H. and Moore, R. G. and Yi, M. and Trigo, M. and Kirchmann, P. and Pathey, L. and Golden, M. S. and Buchholz, Marcel and Metcalf, P. and Parmigiani, F. and Wurth, W. and F{\"o}hlisch, Alexander and Schuessler-Langeheine, Christian and Duerr, H. A.}, title = {Speed limit of the insulator-metal transition in magnetite}, series = {Nature materials}, volume = {12}, journal = {Nature materials}, number = {10}, publisher = {Nature Publ. Group}, address = {London}, issn = {1476-1122}, doi = {10.1038/NMAT3718}, pages = {882 -- 886}, year = {2013}, abstract = {As the oldest known magnetic material, magnetite (Fe3O4) has fascinated mankind for millennia. As the first oxide in which a relationship between electrical conductivity and fluctuating/localized electronic order was shown(1), magnetite represents a model system for understanding correlated oxides in general. Nevertheless, the exact mechanism of the insulator-metal, or Verwey, transition has long remained inaccessible(2-8). Recently, three- Fe- site lattice distortions called trimeronswere identified as the characteristic building blocks of the low-temperature insulating electronically ordered phase(9). Here we investigate the Verwey transition with pump- probe X- ray diffraction and optical reflectivity techniques, and show how trimerons become mobile across the insulator-metal transition. We find this to be a two- step process. After an initial 300 fs destruction of individual trimerons, phase separation occurs on a 1.5 +/- 0.2 ps timescale to yield residual insulating and metallic regions. This work establishes the speed limit for switching in future oxide electronics(10).}, language = {en} } @article{OstromObergXinetal.2015, author = {Ostrom, H. and Oberg, H. and Xin, H. and Larue, J. and Beye, Martin and Gladh, J. and Ng, M. L. and Sellberg, J. A. and Kaya, S. and Mercurio, G. and Nordlund, D. and Hantschmann, Markus and Hieke, F. and Kuehn, D. and Schlotter, W. F. and Dakovski, G. L. and Turner, J. J. and Minitti, M. P. and Mitra, A. and Moeller, S. P. and F{\"o}hlisch, Alexander and Wolf, M. and Wurth, W. and Persson, Mats and Norskov, J. K. and Abild-Pedersen, Frank and Ogasawara, Hirohito and Pettersson, Lars G. M. and Nilsson, A.}, title = {Probing the transition state region in catalytic CO oxidation on Ru}, series = {Science}, volume = {347}, journal = {Science}, number = {6225}, publisher = {American Assoc. for the Advancement of Science}, address = {Washington}, issn = {0036-8075}, doi = {10.1126/science.1261747}, pages = {978 -- 982}, year = {2015}, abstract = {Femtosecond x-ray laser pulses are used to probe the carbon monoxide (CO) oxidation reaction on ruthenium (Ru) initiated by an optical laser pulse. On a time scale of a few hundred femtoseconds, the optical laser pulse excites motions of CO and oxygen (O) on the surface, allowing the reactants to collide, and, with a transient close to a picosecond (ps), new electronic states appear in the OK-edge x-ray absorption spectrum. Density functional theory calculations indicate that these result from changes in the adsorption site and bond formation between CO and O with a distribution of OC-O bond lengths close to the transition state (TS). After 1 ps, 10\% of the CO populate the TS region, which is consistent with predictions based on a quantum oscillator model.}, language = {en} } @misc{ShpritsAngelopoulosRusselletal.2017, author = {Shprits, Yuri and Angelopoulos, V. and Russell, C. T. and Strangeway, R. J. and Runov, A. and Turner, D. and Caron, R. and Cruce, P. and Leneman, D. and Michaelis, I. and Petrov, V. and Panasyuk, M. and Yashin, I. and Drozdov, Alexander and Russell, C. L. and Kalegaev, V. and Nazarkov, I. and Clemmons, J. H.}, title = {Scientific Objectives of Electron Losses and Fields INvestigation Onboard Lomonosov Satellite}, series = {Space science reviews}, volume = {214}, journal = {Space science reviews}, number = {1}, publisher = {Springer}, address = {Dordrecht}, issn = {0038-6308}, doi = {10.1007/s11214-017-0455-4}, pages = {19}, year = {2017}, abstract = {The objective of the Electron Losses and Fields INvestigation on board the Lomonosov satellite ( ELFIN-L) project is to determine the energy spectrum of precipitating energetic electrons and ions and, together with other polar-orbiting and equatorial missions, to better understand the mechanisms responsible for scattering these particles into the atmosphere. This mission will provide detailed measurements of the radiation environment at low altitudes. The 400-500 km sun-synchronous orbit of Lomonosov is ideal for observing electrons and ions precipitating into the atmosphere. This mission provides a unique opportunity to test the instruments. Similar suite of instruments will be flown in the future NSF-and NASA-supported spinning CubeSat ELFIN satellites which will augment current measurements by providing detailed information on pitch-angle distributions of precipitating and trapped particles.}, language = {en} } @article{BoydSpenceHuangetal.2016, author = {Boyd, A. J. and Spence, Harlan E. and Huang, Chia-Lin and Reeves, Geoffrey D. and Baker, Daniel N. and Turner, D. L. and Claudepierre, Seth G. and Fennell, Joseph F. and Blake, J. Bernard and Shprits, Yuri}, title = {Statistical properties of the radiation belt seed population}, series = {Journal of geophysical research : Space physics}, volume = {121}, journal = {Journal of geophysical research : Space physics}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1002/2016JA022652}, pages = {7636 -- 7646}, year = {2016}, abstract = {We present a statistical analysis of phase space density data from the first 26 months of the Van Allen Probes mission. In particular, we investigate the relationship between the tens and hundreds of keV seed electrons and >1 MeV core radiation belt electron population. Using a cross-correlation analysis, we find that the seed and core populations are well correlated with a coefficient of approximate to 0.73 with a time lag of 10-15 h. We present evidence of a seed population threshold that is necessary for subsequent acceleration. The depth of penetration of the seed population determines the inner boundary of the acceleration process. However, we show that an enhanced seed population alone is not enough to produce acceleration in the higher energies, implying that the seed population of hundreds of keV electrons is only one of several conditions required for MeV electron radiation belt acceleration.}, language = {en} } @article{KelesMallomvonEssenetal.2021, author = {Keles, Engin and Mallom, Matthias and von Essen, Carolina and Caroll, Thorsten A. and Alexoudi, Xanthippi and Pino, Lorenzo and Ilyin, Ilya and Poppenh{\"a}ger, Katja and Kitzmann, Daniel and Nascimbeni, Valerino and Turner, Jake D. and Strassmeier, Klaus G.}, title = {The potassium absorption on HD189733b and HD209458b}, series = {Monthly Notices of the Royal Astronomical Society: Letters}, volume = {489}, journal = {Monthly Notices of the Royal Astronomical Society: Letters}, number = {1}, publisher = {Oxford Univ. Press}, address = {Oxford}, doi = {10.1093/mnrasl/slz123}, pages = {L37 -- L41}, year = {2021}, abstract = {In this work, we investigate the potassium excess absorption around 7699 {\AA} of the exoplanets HD189733b and HD209458b. For this purpose, we used high-spectral resolution transit observations acquired with the 2 × 8.4 m Large Binocular Telescope (LBT) and the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI). For a bandwidth of 0.8 {\AA}, we present a detection >7σ with an absorption level of 0.18 per cent for HD189733b. Applying the same analysis to HD209458b, we can set 3σ upper limit of 0.09 per cent, even though we do not detect a K-excess absorption. The investigation suggests that the K feature is less present in the atmosphere of HD209458b than in the one of HD189733b. This comparison confirms previous claims that the atmospheres of these two planets must have fundamentally different properties.}, language = {en} } @article{EigmuellerChaushevGillenetal.2019, author = {Eigm{\"u}ller, Philipp and Chaushev, Alexander and Gillen, Edward and Smith, Alexis and Nielsen, Louise D. and Turner, Oliver and Csizmadia, Szilard and Smalley, Barry and Bayliss, Daniel and Belardi, Claudia and Bouchy, Francois and Burleigh, Matthew R. and Cabrera, Juan and Casewell, Sarah L. and Chazelas, Bruno and Cooke, Benjamin F. and Erikson, Anders and Gansicke, Boris T. and Guenther, Maximilian N. and Goad, Michael R. and Grange, Andrew and Jackman, James A. G. and Jenkins, James S. and McCormac, James and Moyano, Maximiliano and Pollacco, Don and Poppenh{\"a}ger, Katja and Queloz, Didier and Raynard, Liam and Rauer, Heike and Udry, Stephane and Walker, Simon. R. and Watson, Christopher A. and West, Richard G. and Wheatley, Peter J.}, title = {NGTS-5b}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {625}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201935206}, pages = {9}, year = {2019}, abstract = {Context. Planetary population analysis gives us insight into formation and evolution processes. For short-period planets, the sub-Jovian desert has been discussed in recent years with regard to the planet population in the mass/period and radius/period parameter space without taking stellar parameters into account. The Next Generation Transit Survey (NGTS) is optimised for detecting planets in this regime, which allows for further analysis of the sub-Jovian desert. Aims. With high-precision photometric surveys (e.g. with NGTS and TESS), which aim to detect short period planets especially around M/K-type host stars, stellar parameters need to be accounted for when empirical data are compared to model predictions. Presenting a newly discovered planet at the boundary of the sub-Jovian desert, we analyse its bulk properties and use it to show the properties of exoplanets that border the sub-Jovian desert. Methods. Using NGTS light curve and spectroscopic follow-up observations, we confirm the planetary nature of planet NGTS-5b and determine its mass. Using exoplanet archives, we set the planet in context with other discoveries. Results. NGTS-5b is a short-period planet with an orbital period of 3.3569866 +/- 0.0000026 days. With a mass of 0.229 +/- 0.037 M-Jup and a radius of 1.136 +/- 0.023 R-Jup, it is highly inflated. Its mass places it at the upper boundary of the sub-Jovian desert. Because the host is a K2 dwarf, we need to account for the stellar parameters when NGTS-5b is analysed with regard to planet populations. Conclusions. With red-sensitive surveys (e.g. with NGTS and TESS), we expect many more planets around late-type stars to be detected. An empirical analysis of the sub-Jovian desert should therefore take stellar parameters into account.}, language = {en} } @article{KelesKitzmannMallonnetal.2020, author = {Keles, Engin and Kitzmann, Daniel and Mallonn, Matthias and Alexoudi, Xanthippi and Fossati, Luca and Pino, Lorenzo and Seidel, Julia Victoria and Caroll, Thorsten A. and Steffen, M. and Ilyin, Ilya and Poppenh{\"a}ger, Katja and Strassmeier, Klaus G. and von Essen, Carolina and Nascimbeni, Valerio and Turner, Jake D.}, title = {Probing the atmosphere of HD189733b with the Na i and K i lines}, series = {Monthly Notices of the Royal Astronomical Society}, volume = {498}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, publisher = {Oxford Univ. Press}, address = {Oxford}, doi = {10.1093/mnras/staa2435}, pages = {1033}, year = {2020}, abstract = {High spectral resolution transmission spectroscopy is a powerful tool to characterize exoplanet atmospheres. Especially for hot Jupiters, this technique is highly relevant, due to their high-altitude absorption, e.g. from resonant sodium (Na i) and potassium (K i) lines. We resolve the atmospheric K i absorption on HD189733b with the aim to compare the resolved K i line and previously obtained high-resolution Na i-D line observations with synthetic transmission spectra. The line profiles suggest atmospheric processes leading to a line broadening of the order of ∼10 km/s for the Na i-D lines and only a few km/s for the K i line. The investigation hints that either the atmosphere of HD189733b lacks a significant amount of K i or the alkali lines probe different atmospheric regions with different temperature, which could explain the differences we see in the resolved absorption lines.}, language = {en} } @article{KunnusJosefssonRajkovicetal.2016, author = {Kunnus, Kristjan and Josefsson, I. and Rajkovic, Ivan and Schreck, Simon and Quevedo, Wilson and Beye, Martin and Weniger, C. and Gruebel, S. and Scholz, M. and Nordlund, D. and Zhang, W. and Hartsock, R. W. and Gaffney, K. J. and Schlotter, W. F. and Turner, J. J. and Kennedy, B. and Hennies, F. and de Groot, F. M. F. and Techert, S. and Odelius, Michael and Wernet, Ph. and F{\"o}hlisch, Alexander}, title = {Identification of the dominant photochemical pathways and mechanistic insights to the ultrafast ligand exchange of Fe(CO)(5) to Fe(CO)(4)EtOH}, series = {Structural dynamics}, volume = {3}, journal = {Structural dynamics}, publisher = {American Institute of Physics}, address = {Washington}, issn = {2329-7778}, doi = {10.1063/1.4941602}, pages = {16}, year = {2016}, abstract = {We utilized femtosecond time-resolved resonant inelastic X-ray scattering and ab initio theory to study the transient electronic structure and the photoinduced molecular dynamics of a model metal carbonyl photocatalyst Fe(CO)(5) in ethanol solution. We propose mechanistic explanation for the parallel ultrafast intra-molecular spin crossover and ligation of the Fe(CO)(4) which are observed following a charge transfer photoexcitation of Fe(CO)(5) as reported in our previous study [ Wernet et al., Nature 520, 78 (2015)]. We find that branching of the reaction pathway likely happens in the (1)A(1) state of Fe(CO)(4). A sub-picosecond time constant of the spin crossover from B-1(2) to B-3(2) is rationalized by the proposed B-1(2) -> (1)A(1) -> B-3(2) mechanism. Ultrafast ligation of the B-1(2) Fe(CO)(4) state is significantly faster than the spin-forbidden and diffusion limited ligation process occurring from the B-3(2) Fe(CO)(4) ground state that has been observed in the previous studies. We propose that the ultrafast ligation occurs via B-1(2) -> (1)A(1) -> (1)A'Fe(CO)(4)EtOH pathway and the time scale of the (1)A(1) Fe(CO)(4) state ligation is governed by the solute-solvent collision frequency. Our study emphasizes the importance of understanding the interaction of molecular excited states with the surrounding environment to explain the relaxation pathways of photoexcited metal carbonyls in solution. (C) 2016 Author(s).}, language = {en} } @article{KubinKernGuletal.2017, author = {Kubin, Markus and Kern, Jan and Gul, Sheraz and Kroll, Thomas and Chatterjee, Ruchira and Loechel, Heike and Fuller, Franklin D. and Sierra, Raymond G. and Quevedo, Wilson and Weniger, Christian and Rehanek, Jens and Firsov, Anatoly and Laksmono, Hartawan and Weninger, Clemens and Alonso-Mori, Roberto and Nordlund, Dennis L. and Lassalle-Kaiser, Benedikt and Glownia, James M. and Krzywinski, Jacek and Moeller, Stefan and Turner, Joshua J. and Minitti, Michael P. and Dakovski, Georgi L. and Koroidov, Sergey and Kawde, Anurag and Kanady, Jacob S. and Tsui, Emily Y. and Suseno, Sandy and Han, Zhiji and Hill, Ethan and Taguchi, Taketo and Borovik, Andrew S. and Agapie, Theodor and Messinger, Johannes and Erko, Alexei and F{\"o}hlisch, Alexander and Bergmann, Uwe and Mitzner, Rolf and Yachandra, Vittal K. and Yano, Junko and Wernet, Philippe}, title = {Soft x-ray absorption spectroscopy of metalloproteins and high-valent metal-complexes at room temperature using free-electron lasers}, series = {Structural dynamics}, volume = {4}, journal = {Structural dynamics}, publisher = {American Institute of Physics}, address = {Melville}, issn = {2329-7778}, doi = {10.1063/1.4986627}, pages = {16}, year = {2017}, abstract = {X-ray absorption spectroscopy at the L-edge of 3d transition metals provides unique information on the local metal charge and spin states by directly probing 3d-derived molecular orbitals through 2p-3d transitions. However, this soft x-ray technique has been rarely used at synchrotron facilities for mechanistic studies of metalloenzymes due to the difficulties of x-ray-induced sample damage and strong background signals from light elements that can dominate the low metal signal. Here, we combine femtosecond soft x-ray pulses from a free-electron laser with a novel x-ray fluorescence-yield spectrometer to overcome these difficulties. We present L-edge absorption spectra of inorganic high-valent Mn complexes (Mn similar to 6-15 mmol/l) with no visible effects of radiation damage. We also present the first L-edge absorption spectra of the oxygen evolving complex (Mn4CaO5) in Photosystem II (Mn < 1 mmol/l) at room temperature, measured under similar conditions. Our approach opens new ways to study metalloenzymes under functional conditions. (C) 2017 Author(s).}, language = {en} } @article{KrollKernKubinetal.2016, author = {Kroll, Thomas and Kern, Jan and Kubin, Markus and Ratner, Daniel and Gul, Sheraz and Fuller, Franklin D. and L{\"o}chel, Heike and Krzywinski, Jacek and Lutman, Alberto and Ding, Yuantao and Dakovski, Georgi L. and Moeller, Stefan and Turner, Joshua J. and Alonso-Mori, Roberto and Nordlund, Dennis L. and Rehanek, Jens and Weniger, Christian and Firsov, Alexander and Brzhezinskaya, Maria and Chatterjee, Ruchira and Lassalle-Kaiser, Benedikt and Sierra, Raymond G. and Laksmono, Hartawan and Hill, Ethan and Borovik, Andrew S. and Erko, Alexei and F{\"o}hlisch, Alexander and Mitzner, Rolf and Yachandra, Vittal K. and Yano, Junko and Wernet, Philippe and Bergmann, Uwe}, title = {X-ray absorption spectroscopy using a self-seeded soft X-ray free-electron laser}, series = {Optics express : the international electronic journal of optics}, volume = {24}, journal = {Optics express : the international electronic journal of optics}, publisher = {Optical Society of America}, address = {Washington}, issn = {1094-4087}, doi = {10.1364/OE.24.022469}, pages = {22469 -- 22480}, year = {2016}, abstract = {X-ray free electron lasers (XFELs) enable unprecedented new ways to study the electronic structure and dynamics of transition metal systems. L-edge absorption spectroscopy is a powerful technique for such studies and the feasibility of this method at XFELs for solutions and solids has been demonstrated. However, the required x-ray bandwidth is an order of magnitude narrower than that of self-amplified spontaneous emission (SASE), and additional monochromatization is needed. Here we compare L-edge x-ray absorption spectroscopy (XAS) of a prototypical transition metal system based on monochromatizing the SASE radiation of the linac coherent light source (LCLS) with a new technique based on self-seeding of LCLS. We demonstrate how L-edge XAS can be performed using the self-seeding scheme without the need of an additional beam line monochromator. We show how the spectral shape and pulse energy depend on the undulator setup and how this affects the x-ray spectroscopy measurements. (C) 2016 Optical Society of America}, language = {en} }