TY - JOUR A1 - Ortiz-Amezcua, Pablo A1 - Guerrero-Rascado, Juan Luis A1 - Jose Granados-Munoz, Maria A1 - Benavent-Oltra, Jose Antonio A1 - Böckmann, Christine A1 - Samaras, Stefanos A1 - Stachlewska, Iwona Sylwia A1 - Janicka, Lucja A1 - Baars, Holger A1 - Bohlmann, Stephanie A1 - Alados-Arboledas, Lucas T1 - Microphysical characterization of long-range transported biomass burning particles from North America at three EARLINET stations JF - Atmospheric Chemistry and Physics N2 - Strong events of long-range transported biomass burning aerosol were detected during July 2013 at three EARLINET (European Aerosol Research Lidar Network) stations, namely Granada (Spain), Leipzig (Germany) and Warsaw (Poland). Satellite observations from MODIS (Moderate Resolution Imaging Spectroradiometer) and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) instruments, as well as modeling tools such as HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) and NAAPS (Navy Aerosol Analysis and Prediction System), have been used to estimate the sources and transport paths of those North American forest fire smoke particles. A multiwavelength Raman lidar technique was applied to obtain vertically resolved particle optical properties, and further inversion of those properties with a regularization algorithm allowed for retrieving microphysical information on the studied particles. The results highlight the presence of smoke layers of 1-2 km thickness, located at about 5 km a.s.l. altitude over Granada and Leipzig and around 2.5 km a.s.l. at Warsaw. These layers were intense, as they accounted for more than 30% of the total AOD (aerosol optical depth) in all cases, and presented optical and microphysical features typical for different aging degrees: color ratio of lidar ratios (LR532/LR355) around 2, alpha-related angstrom exponents of less than 1, effective radii of 0.3 mu m and large values of single scattering albedos (SSA), nearly spectrally independent. The intensive microphysical properties were compared with columnar retrievals form co-located AERONET (Aerosol Robotic Network) stations. The intensity of the layers was also characterized in terms of particle volume concentration, and then an experimental relationship between this magnitude and the particle extinction coefficient was established. Y1 - 2017 U6 - https://doi.org/10.5194/acp-17-5931-2017 SN - 1680-7316 SN - 1680-7324 VL - 17 SP - 5931 EP - 5946 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Lechleitner, Franziska A. A1 - Breitenbach, Sebastian Franz Martin A1 - Rehfeld, Kira A1 - Ridley, Harriet E. A1 - Asmerom, Yemane A1 - Prufer, Keith M. A1 - Marwan, Norbert A1 - Goswami, Bedartha A1 - Kennett, Douglas J. A1 - Aquino, Valorie V. A1 - Polyak, Victor A1 - Haug, Gerald H. A1 - Eglinton, Timothy I. A1 - Baldini, James U. L. T1 - Tropical rainfall over the last two millennia: evidence for a low-latitude hydrologic seesaw JF - Scientific reports N2 - The presence of a low-to mid-latitude interhemispheric hydrologic seesaw is apparent over orbital and glacial-interglacial timescales, but its existence over the most recent past remains unclear. Here we investigate, based on climate proxy reconstructions from both hemispheres, the inter-hemispherical phasing of the Intertropical Convergence Zone (ITCZ) and the low-to mid-latitude teleconnections in the Northern Hemisphere over the past 2000 years. A clear feature is a persistent southward shift of the ITCZ during the Little Ice Age until the beginning of the 19th Century. Strong covariation between our new composite ITCZ-stack and North Atlantic Oscillation (NAO) records reveals a tight coupling between these two synoptic weather and climate phenomena over decadal-to-centennial timescales. This relationship becomes most apparent when comparing two precisely dated, high-resolution paleorainfall records from Belize and Scotland, indicating that the low-to mid-latitude teleconnection was also active over annual-decadal timescales. It is likely a combination of external forcing, i.e., solar and volcanic, and internal feedbacks, that drives the synchronous ITCZ and NAO shifts via energy flux perturbations in the tropics. Y1 - 2017 U6 - https://doi.org/10.1038/srep45809 SN - 2045-2322 VL - 7 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Sandev, Trifce A1 - Sokolov, Igor M. A1 - Metzler, Ralf A1 - Chechkin, Aleksei V. T1 - Beyond monofractional kinetics JF - Chaos, solitons & fractals : applications in science and engineering ; an interdisciplinary journal of nonlinear science N2 - We discuss generalized integro-differential diffusion equations whose integral kernels are not of a simple power law form, and thus these equations themselves do not belong to the family of fractional diffusion equations exhibiting a monoscaling behavior. They instead generate a broad class of anomalous nonscaling patterns, which correspond either to crossovers between different power laws, or to a non-power-law behavior as exemplified by the logarithmic growth of the width of the distribution. We consider normal and modified forms of these generalized diffusion equations and provide a brief discussion of three generic types of integral kernels for each form, namely, distributed order, truncated power law and truncated distributed order kernels. For each of the cases considered we prove the non-negativity of the solution of the corresponding generalized diffusion equation and calculate the mean squared displacement. (C) 2017 Elsevier Ltd. All rights reserved. KW - Distributed order diffusion-wave equations KW - Complete Bernstein function KW - Completely monotone function Y1 - 2017 U6 - https://doi.org/10.1016/j.chaos.2017.05.001 SN - 0960-0779 SN - 1873-2887 VL - 102 SP - 210 EP - 217 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kegelmann, Lukas A1 - Wolff, Christian Michael A1 - Awino, Celline A1 - Lang, Felix A1 - Unger, Eva L. A1 - Korte, Lars A1 - Dittrich, Thomas A1 - Neher, Dieter A1 - Rech, Bernd A1 - Albrecht, Steve T1 - It Takes Two to Tango-Double-Layer Selective Contacts in Perovskite Solar Cells for Improved Device Performance and Reduced Hysteresis JF - ACS applied materials & interfaces N2 - Solar cells made from inorganic organic perovskites have gradually approached market requirements as their efficiency and stability have improved tremendously in recent years. Planar low-temperature processed perovskite solar cells are advantageous for possible large-scale production but are more prone to exhibiting photocurrent hysteresis, especially in the regular n-i-p structure. Here, a systematic characterization of different electron selective contacts with a variety of chemical and electrical properties in planar n-i-p devices processed below 180 degrees C is presented. The inorganic metal oxides TiO2 and SnO2, the organic fullerene derivatives C-60, PCBM, and ICMA, as well as double-layers with a metal oxide/PCBM structure are used as electron transport materials (ETMs). Perovskite layers deposited atop, the different ETMs with the herein applied fabrication method show a similar morphology according to scanning electron microscopy. Further, surface photovoltage spectroscopy measurements indicate comparable perovskite absorber qualities on all ETMs, except TiO2, which shows a more prominent influence of defect states. Transient photoluminescence studies together with current voltage scans over a broad range of scan speeds reveal faster charge extraction, less pronounced hysteresis effects, and higher efficiencies for devices with fullerene compared to those with metal oxide ETMs. Beyond this, only double-layer ETM structures substantially diminish hysteresis effects for all performed scan speeds and strongly enhance the power conversion efficiency up to a champion stabilized value of 18.0%. The results indicate reduced recombination losses for a double-layer TiO2/PCBM contact design: First, a reduction of shunt paths through the fullerene to the ITO layer. Second, an improved hole blocking by the wide band gap metal oxide. Third, decreased transport losses due to an energetically more favorable contact, as implied by photoelectron spectroscopy measurements. The herein demonstrated improvements of multilayer selective contacts may serve as a general design guideline for perovskite solar cells. KW - perovskite solar cell KW - electron contact KW - double-layer KW - regular planar architecture KW - hysteresis KW - fullerene KW - metal oxide Y1 - 2017 U6 - https://doi.org/10.1021/acsami.7b00900 SN - 1944-8244 VL - 9 SP - 17246 EP - 17256 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Jošt, Marko A1 - Albrecht, Steve A1 - Kegelmann, Lukas A1 - Wolff, Christian Michael A1 - Lang, Felix A1 - Lipovšek, Benjamin A1 - Krč, Janez A1 - Korte, Lars A1 - Neher, Dieter A1 - Rech, Bernd A1 - Topič, Marko T1 - Efficient light management by textured nanoimprinted layers for perovskite solar cells JF - ACS photonics N2 - Inorganic-organic perovskites like methylammonium-lead-iodide have proven to be an effective class of 17 materials for fabricating efficient solar cells. To improve their performance, light management techniques using textured surfaces, similar to those used in established solar cell technologies, should be considered. Here, we apply a light management foil created by UV nanoimprint lithography on the glass side of an inverted (p-i-n) perovskite solar cell with 16.3% efficiency. The obtained 1 mA cm(-2) increase in the short-circuit current density translates to a relative improvement in cell performance of 5%, which results in a power conversion efficiency of 17.1%. Optical 3D simulations based on experimentally obtained parameters were used to support the experimental findings. A good match between the simulated and experimental data was obtained, validating the model. Optical simulations reveal that the main improvement in device performance is due to a reduction in total reflection and that relative improvement in the short-circuit current density of up to 10% is possible for large-area devices. Therefore, our results present the potential of light management foils for improving the device performance of perovskite solar cells and pave the way for further use of optical simulations in the field of perovskite solar cells. KW - perovskite solar cells KW - antireflection KW - light management KW - UV nanoimprint lithography KW - optical simulations Y1 - 2017 U6 - https://doi.org/10.1021/acsphotonics.7b00138 SN - 2330-4022 VL - 4 SP - 1232 EP - 1239 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Vandewal, Koen A1 - Benduhn, Johannes A1 - Schellhammer, Karl Sebastian A1 - Vangerven, Tim A1 - Rückert, Janna E. A1 - Piersimoni, Fortunato A1 - Scholz, Reinhard A1 - Zeika, Olaf A1 - Fan, Yeli A1 - Barlow, Stephen A1 - Neher, Dieter A1 - Marder, Seth R. A1 - Manca, Jean A1 - Spoltore, Donato A1 - Cuniberti, Gianaurelio A1 - Ortmann, Frank T1 - Absorption Tails of Donor BT - C-60 Blends Provide Insight into Thermally Activated Charge-Transfer Processes and Polaron Relaxation JF - Journal of the American Chemical Society N2 - In disordered organic semiconductors, the transfer of a rather localized charge carrier from one site to another triggers a deformation of the molecular structure quantified by the intramolecular relaxation energy. A similar structural relaxation occurs upon population of intermolecular charge-transfer (CT) states formed at organic electron donor (D)-acceptor (A) interfaces. Weak CT absorption bands for D A complexes occur at photon energies below the optical gaps of both the donors and the C-60 acceptor as a result of optical transitions from the neutral ground state to the ionic CT state. In this work, we show that temperature-activated intramolecular vibrations of the ground state play a major role in determining the line shape of such CT absorption bands. This allows us to extract values for the relaxation energy related to the geometry change from neutral to ionic CT complexes. Experimental values for the relaxation energies of 20 D:C-60 CT complexes correlate with values calculated within density functional theory. These results provide an experimental method for determining the polaron relaxation energy in solid-state organic D-A blends and show the importance of a reduced relaxation energy, which we introduce to characterize thermally activated CT processes. Y1 - 2017 U6 - https://doi.org/10.1021/jacs.6b12857 SN - 0002-7863 VL - 139 IS - 4 SP - 1699 EP - 1704 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - De Angelis, A. A1 - Tatischeff, V. A1 - Tavani, M. A1 - Oberlack, U. A1 - Grenier, I. A1 - Hanloni, L. A1 - Walter, R. A1 - Argan, A. A1 - Von Ballmoos, P. A1 - Bulgarelli, A. A1 - Donnarumma, I. A1 - Hernanz, M. A1 - Kuvvetli, I. A1 - Pearce, M. A1 - Zdziarski, A. A1 - Aboudan, A. A1 - Ajello, M. A1 - Ambrosi, G. A1 - Bernard, D. A1 - Bernardini, E. A1 - Bonvicini, V. A1 - Brogna, A. A1 - Branchesi, M. A1 - Budtz-Jorgensen, C. A1 - Bykov, A. M. A1 - Campana, R. A1 - Cardillo, M. A1 - Coppi, P. A1 - De Martino, D. A1 - Diehl, R. A1 - Doro, M. A1 - Fioretti, V. A1 - Funk, S. A1 - Ghisellini, G. A1 - Grove, E. A1 - Hamadache, C. A1 - Hartmann, D. H. A1 - Hayashida, M. A1 - Isern, J. A1 - Kanbach, G. A1 - Kiener, J. A1 - Knodlseder, J. A1 - Labanti, C. A1 - Laurent, P. A1 - Limousin, O. A1 - Longo, F. A1 - Mannheim, K. A1 - Marisaldi, M. A1 - Martinez, M. A1 - Mazziotta, Mario Nicola A1 - McEnery, J. A1 - Mereghetti, S. A1 - Minervini, G. A1 - Moiseev, A. A1 - Morselli, A. A1 - Nakazawa, K. A1 - Orleanski, P. A1 - Paredes, J. M. A1 - Patricelli, B. A1 - Pevre, J. A1 - Piano, G. A1 - Pohl, Martin A1 - Ramarijaona, H. A1 - Rando, R. A1 - Reichardt, I. A1 - Roncadelli, M. A1 - Silva, R. A1 - Tavecchio, F. A1 - Thompson, D. J. A1 - Turolla, R. A1 - Ulyanov, A. A1 - Vacchi, A. A1 - Wu, X. A1 - Zoglauer, A. T1 - The e-ASTROGAM mission Exploring the extreme Universe with gamma rays in the MeV - GeV range JF - Experimental astronomy : an international journal on astronomical instrumentation and data analysis N2 - e-ASTROGAM (‘enhanced ASTROGAM’) is a breakthrough Observatory space mission, with a detector composed by a Silicon tracker, a calorimeter, and an anticoincidence system, dedicated to the study of the non-thermal Universe in the photon energy range from 0.3 MeV to 3 GeV – the lower energy limit can be pushed to energies as low as 150 keV, albeit with rapidly degrading angular resolution, for the tracker, and to 30 keV for calorimetric detection. The mission is based on an advanced space-proven detector technology, with unprecedented sensitivity, angular and energy resolution, combined with polarimetric capability. Thanks to its performance in the MeV-GeV domain, substantially improving its predecessors, e-ASTROGAM will open a new window on the non-thermal Universe, making pioneering observations of the most powerful Galactic and extragalactic sources, elucidating the nature of their relativistic outflows and their effects on the surroundings. With a line sensitivity in the MeV energy range one to two orders of magnitude better than previous generation instruments, e-ASTROGAM will determine the origin of key isotopes fundamental for the understanding of supernova explosion and the chemical evolution of our Galaxy. The mission will provide unique data of significant interest to a broad astronomical community, complementary to powerful observatories such as LIGO-Virgo-GEO600-KAGRA, SKA, ALMA, E-ELT, TMT, LSST, JWST, Athena, CTA, IceCube, KM3NeT, and the promise of eLISA. KW - High-Energy Gamma-Ray Astronomy KW - High-Energy Astrophysics KW - Nuclear Astrophysics KW - Compton and Pair Creation Telescope KW - Gamma-Ray Bursts KW - Active Galactic Nuclei KW - Jets KW - Outflows KW - Multiwavelength Observations of the Universe KW - Counterparts of gravitational waves KW - Fermi KW - Dark Matter KW - Nucleosynthesis KW - Early Universe KW - Supernovae KW - Cosmic Rays KW - Cosmic Antimatter Y1 - 2017 U6 - https://doi.org/10.1007/s10686-017-9533-6 SN - 0922-6435 SN - 1572-9508 VL - 44 SP - 25 EP - 82 PB - Springer CY - Dordrecht ER - TY - GEN A1 - Fraschetti, Federico A1 - Pohl, Martin T1 - Two-zone model for the broadband crab nebula spectrum BT - microscopic interpretation T2 - The European physical journal : Web of Conferences : proceedings N2 - We develop a simple two-zone interpretation of the broadband baseline Crab nebula spectrum between 10(-5) eV and similar to 100 TeV by using two distinct log-parabola energetic electrons distributions. We determine analytically the very-high energy photon spectrum as originated by inverse-Compton scattering of the far-infrared soft ambient photons within the nebula off a first population of electrons energized at the nebula termination shock. The broad and flat 200 GeV peak jointly observed by Fermi/LAT and MAGIC is naturally reproduced. The synchrotron radiation from a second energetic electron population explains the spectrum from the radio range up to similar to 10 keV. We infer from observations the energy dependence of the microscopic probability of remaining in proximity of the shock of the accelerating electrons. Y1 - 2017 U6 - https://doi.org/10.1051/epjconf/201713602009 SN - 2100-014X VL - 136 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Kobzar, Oleh A1 - Niemiec, Jacek A1 - Pohl, Martin A1 - Bohdan, Artem T1 - Spatio-temporal evolution of the non-resonant instability in shock precursors of young supernova remnants JF - Monthly notices of the Royal Astronomical Society N2 - A non-resonant cosmic ray (CR) current-driven instability may operate in the shock precursors of young supernova remnants and be responsible for magnetic-field amplification, plasma heating and turbulence. Earlier simulations demonstrated magnetic-field amplification, and in kinetic studies a reduction of the relative drift between CRs and thermal plasma was observed as backreaction. However, all published simulations used periodic boundary conditions, which do not account for mass conservation in decelerating flows and only allow the temporal development to be studied. Here we report results of fully kinetic particle-in-cell simulations with open boundaries that permit inflow of plasma on one side of the simulation box and outflow at the other end, hence allowing an investigation of both the temporal and the spatial development of the instability. Magnetic-field amplification proceeds as in studies with periodic boundaries and, observed here for the first time, the reduction of relative drifts causes the formation of a shock-like compression structure at which a fraction of the plasma ions are reflected. Turbulent electric field generated by the non-resonant instability inelastically scatters CRs, modifying and anisotropizing their energy distribution. Spatial CR scattering is compatible with Bohm diffusion. Electromagnetic turbulence leads to significant non-adiabatic heating of the background plasma maintaining bulk equipartition between ions and electrons. The highest temperatures are reached at sites of large-amplitude electrostatic fields. Ion spectra show supra-thermal tails resulting from stochastic scattering in the turbulent electric field. Together, these modifications in the plasma flow will affect the properties of the shock and particle acceleration there. KW - acceleration of particles KW - shock waves KW - turbulence KW - methods: numerical KW - cosmic rays KW - ISM: supernova remnants Y1 - 2017 U6 - https://doi.org/10.1093/mnras/stx1201 SN - 0035-8711 SN - 1365-2966 VL - 469 SP - 4985 EP - 4998 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Schubert, Marcel A1 - Frisch, Johannes A1 - Allard, Sybille A1 - Preis, Eduard A1 - Scherf, Ullrich A1 - Koch, Norbert A1 - Neher, Dieter T1 - Tuning side chain and main chain order in a prototypical donor-acceptor copolymer BT - implications for optical, electronic, and photovoltaic characteristics JF - Elementary Processes in Organic Photovoltaics N2 - The recent development of donor–acceptor copolymers has led to an enormous improvement in the performance of organic solar cells and organic field-effect transistors. Here we describe the synthesis, detailed characterisation, and application of a series of structurally modified copolymers to investigate fundamental structure–property relationships in this class of conjugated polymers. The interplay between chemical structure and optoelectronic properties is investigated. These are further correlated to the charge transport and solar cell performance, which allows us to link their chemical structure to the observed physical properties. KW - Aggregate states KW - All-polymer heterojunctions KW - Alternating copolymers KW - Ambipolar charge transport KW - Ambipolar materials KW - Backbone modifications KW - Bilayer solar cells KW - Charge separation KW - Conformational disorder KW - Crystalline phases KW - Donor-acceptor copolymers KW - Electron traps KW - Energetic disorder KW - Energy-level alignment KW - Fermi-level alignment KW - Fermi-level pinning KW - Interface dipole KW - Interlayer KW - Intrachain order KW - Intragap states KW - Microscopic morphology KW - Mobility imbalance KW - Mobility relaxation KW - Monte Carlo simulation KW - Multiple trapping model KW - Nonradiative recombination KW - OFET KW - Open-circuit voltage KW - Optoelectronic properties KW - Partially alternating copolymers KW - Photo-CELIV KW - Photocurrent KW - Photovoltaic gap KW - Polymer intermixing KW - Recombination losses KW - Spectral diffusion KW - Statistical copolymers KW - Stille-type cross-coupling KW - Structure-property relationships KW - Time-dependent mobility KW - Time-of-flight (TOF) KW - Transient photocurrent KW - Ultraviolet photoelectron spectroscopy KW - Vacuum-level alignment KW - X-ray photoelectron spectroscopy Y1 - 2016 SN - 978-3-319-28338-8 SN - 978-3-319-28336-4 U6 - https://doi.org/10.1007/978-3-319-28338-8_10 SN - 0065-3195 VL - 272 SP - 243 EP - 265 PB - Springer CY - Berlin ER - TY - JOUR A1 - Laquai, Frederic A1 - Andrienko, Denis A1 - Deibel, Carsten A1 - Neher, Dieter T1 - Charge carrier generation, recombination, and extraction in polymer-fullerene bulk heterojunction organic solar cells JF - Elementary processes in organic photovoltaics N2 - In this chapter we review the basic principles of photocurrent generation in bulk heterojunction organic solar cells, discuss the loss channels limiting their efficiency, and present case studies of several polymer-fullerene blends. Using steady-state and transient, optical, and electrooptical techniques, we create a precise picture of the fundamental processes that ultimately govern solar cell efficiency. KW - Charge extraction KW - Charge generation KW - Charge recombination KW - Organic solar cells KW - PBT7 KW - PBTTT KW - PCPDTBT Y1 - 2026 SN - 978-3-319-28338-8 SN - 978-3-319-28336-4 U6 - https://doi.org/10.1007/978-3-319-28338-8_11 SN - 0065-3195 VL - 272 SP - 267 EP - 291 PB - Springer CY - Berlin ER - TY - JOUR A1 - Allen, C. A1 - Archambault, S. A1 - Archer, A. A1 - Benbow, W. A1 - Bird, R. A1 - Bourbeau, E. A1 - Brose, Robert A1 - Buchovecky, M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Cardenzana, J. V. A1 - Cerruti, M. A1 - Chen, Xuhui A1 - Christiansen, J. L. A1 - Connolly, M. P. A1 - Cui, W. A1 - Daniel, M. K. A1 - Eisch, J. D. A1 - Falcone, Abe A1 - Feng, Q. A1 - Fernandez-Alonso, M. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Flinders, A. A1 - Fortson, L. A1 - Furniss, A. A1 - Gillanders, G. H. A1 - Griffin, S. A1 - Grube, J. A1 - Huetten, M. A1 - Hakansson, N. A1 - Hanna, D. A1 - Hervet, O. A1 - Holder, J. A1 - Hughes, G. A1 - Humensky, T. B. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kelley-Hoskins, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krause, M. A1 - Krennrich, F. A1 - Kumar, S. A1 - Lang, M. J. A1 - Maier, G. A1 - McArthur, S. A1 - McCann, A. A1 - Meagher, K. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nguyen, T. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, A. N. A1 - Park, N. A1 - Petrashyk, A. A1 - Pichel, A. A1 - Pohl, Martin A1 - Popkow, A. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Reynolds, P. T. A1 - Richards, G. T. A1 - Roache, E. A1 - Rovero, A. C. A1 - Rulten, C. A1 - Sadeh, I. A1 - Santander, Marcos A1 - Sembroski, G. H. A1 - Shahinyan, K. A1 - Telezhinsky, Igor O. A1 - Tucci, J. V. A1 - Tyler, J. A1 - Wakely, S. P. A1 - Weinstein, A. A1 - Wilhelm, Alina A1 - Williams, D. A. T1 - Very-High-Energy gamma-Ray Observations of the Blazar 1ES 2344+514 with VERITAS JF - Monthly notices of the Royal Astronomical Society N2 - We present very-high-energy gamma-ray observations of the BL Lac object 1ES 2344+514 taken by the Very Energetic Radiation Imaging Telescope Array System between 2007 and 2015. 1ES 2344+514 is detected with a statistical significance above the background of 20.8 sigma in 47.2 h (livetime) of observations, making this the most comprehensive very-high-energy study of 1ES 2344+514 to date. Using these observations, the temporal properties of 1ES 2344+514 are studied on short and long times-scales. We fit a constant-flux model to nightly and seasonally binned light curves and apply a fractional variability test to determine the stability of the source on different time-scales. We reject the constant-flux model for the 2007-2008 and 2014-2015 nightly binned light curves and for the long-term seasonally binned light curve at the > 3 sigma level. The spectra of the time-averaged emission before and after correction for attenuation by the extragalactic background light are obtained. The observed time-averaged spectrum above 200 GeV is satisfactorily fitted (x(2)/NDF = 7.89/6) by a power-law function with an index Gamma = 2.46 +/- 0.06(stat) +/- 0.20(sys) and extends to at least 8 TeV. The extragalactic-backgroundlight-deabsorbed spectrum is adequately fit (x(2)/NDF = 6.73/6) by a power-law function with an index Gamma = 2.15 +/- 0.06(stat) +/- 0.20(sys) while an F-test indicates that the power law with an exponential cut-off function provides a marginally better fit (x(2)/NDF = 2.56/5) at the 2.1 sigma level. The source location is found to be consistent with the published radio location and its spatial extent is consistent with a point source. KW - astroparticle physics KW - BL Lacertae objects: individual: 1ES 2344+514=VERJ2347+517 KW - gamma-rays: galaxies Y1 - 2017 U6 - https://doi.org/10.1093/mnras/stx1756 SN - 0035-8711 SN - 1365-2966 VL - 471 SP - 2117 EP - 2123 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Abeysekara, A. U. A1 - Archambault, S. A1 - Archer, A. A1 - Benbow, Wystan A1 - Bird, Ralph A1 - Buchovecky, M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Byrum, K. A1 - Cerruti, M. A1 - Chen, X. A1 - Ciupik, L. A1 - Cui, W. A1 - Dickinson, H. J. A1 - Eisch, J. D. A1 - Errando, M. A1 - Falcone, A. A1 - Feng, Q. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Fortson, L. A1 - Furniss, A. A1 - Gillanders, G. H. A1 - Griffin, S. A1 - Grube, J. A1 - Hutten, M. A1 - Hakansson, N. A1 - Hanna, D. A1 - Holder, J. A1 - Humensky, T. B. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krause, M. A1 - Krennrich, F. A1 - Kumar, S. A1 - Lang, M. J. A1 - Maier, G. A1 - McArthur, S. A1 - McCann, A. A1 - Meagher, K. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nguyen, T. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, A. N. A1 - Park, N. A1 - Pelassa, V. A1 - Pohl, Martin A1 - Popkow, A. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Reynolds, P. T. A1 - Richards, G. T. A1 - Roache, E. A1 - Rulten, C. A1 - Santander, M. A1 - Sembroski, G. H. A1 - Shahinyan, K. A1 - Staszak, D. A1 - Telezhinsky, Igor O. A1 - Tucci, J. V. A1 - Tyler, J. A1 - Wakely, S. P. A1 - Weiner, O. M. A1 - Weinstein, A. A1 - Wilhelm, Alina A1 - Williams, D. A. A1 - Fegan, S. A1 - Giebels, B. A1 - Horan, D. A1 - Berdyugin, A. A1 - Kuan, J. A1 - Lindfors, E. A1 - Nilsson, K. A1 - Oksanen, A. A1 - Prokoph, H. A1 - Reinthal, R. A1 - Takalo, L. A1 - Zefi, F. T1 - A Luminous and Isolated Gamma-Ray Flare from the Blazar B2 1215+30 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - B2 1215+30 is a BL-Lac-type blazar that was first detected at TeV energies by the MAGIC atmospheric Cherenkov telescopes and subsequently confirmed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory with data collected between 2009 and 2012. In 2014 February 08, VERITAS detected a large-amplitude flare from B2. 1215+30 during routine monitoring observations of the blazar 1ES. 1218+304, located in the same field of view. The TeV flux reached 2.4 times the Crab Nebula flux with a variability timescale of <3.6 hr. Multiwavelength observations with Fermi-LAT, Swift, and the Tuorla Observatory revealed a correlated high GeV flux state and no significant optical counterpart to the flare, with a spectral energy distribution where the gamma-ray luminosity exceeds the synchrotron luminosity. When interpreted in the framework of a onezone leptonic model, the observed emission implies a high degree of beaming, with Doppler factor delta > 10, and an electron population with spectral index p < 2.3. KW - BL Lacertae objects: individual (B2 1215+30, VER J1217+301) KW - galaxies: active KW - galaxies: jets KW - galaxies: nuclei KW - gamma rays: galaxies Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/836/2/205 SN - 0004-637X SN - 1538-4357 VL - 836 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Sadovnichii, V. A. A1 - Panasyuk, M. I. A1 - Amelyushkin, A. M. A1 - Bogomolov, V. V. A1 - Benghin, V. V. A1 - Garipov, G. K. A1 - Kalegaev, V. V. A1 - Klimov, P. A. A1 - Khrenov, B. A. A1 - Petrov, V. L. A1 - Sharakin, S. A. A1 - Shirokov, A. V. A1 - Svertilov, S. I. A1 - Zotov, M. Y. A1 - Yashin, I. V. A1 - Gorbovskoy, E. S. A1 - Lipunov, V. M. A1 - Park, I. H. A1 - Lee, J. A1 - Jeong, S. A1 - Kim, M. B. A1 - Jeong, H. M. A1 - Shprits, Yuri Y. A1 - Angelopoulos, V. A1 - Russell, C. T. A1 - Runov, A. A1 - Turner, D. A1 - Strangeway, R. J. A1 - Caron, R. A1 - Biktemerova, S. A1 - Grinyuk, A. A1 - Lavrova, M. A1 - Tkachev, L. A1 - Tkachenko, A. A1 - Martinez, O. A1 - Salazar, H. A1 - Ponce, E. T1 - "Lomonosov" Satellite-Space Observatory to Study Extreme Phenomena in Space JF - Space science reviews N2 - The "Lomonosov" space project is lead by Lomonosov Moscow State University in collaboration with the following key partners: Joint Institute for Nuclear Research, Russia, University of California, Los Angeles (USA), University of Pueblo (Mexico), Sungkyunkwan University (Republic of Korea) and with Russian space industry organi-zations to study some of extreme phenomena in space related to astrophysics, astroparticle physics, space physics, and space biology. The primary goals of this experiment are to study: -Ultra-high energy cosmic rays (UHECR) in the energy range of the Greizen-ZatsepinKuzmin (GZK) cutoff; -Ultraviolet (UV) transient luminous events in the upper atmosphere; -Multi-wavelength study of gamma-ray bursts in visible, UV, gamma, and X-rays; -Energetic trapped and precipitated radiation (electrons and protons) at low-Earth orbit (LEO) in connection with global geomagnetic disturbances; -Multicomponent radiation doses along the orbit of spacecraft under different geomagnetic conditions and testing of space segments of optical observations of space-debris and other space objects; -Instrumental vestibular-sensor conflict of zero-gravity phenomena during space flight. This paper is directed towards the general description of both scientific goals of the project and scientific equipment on board the satellite. The following papers of this issue are devoted to detailed descriptions of scientific instruments. KW - Gamma-ray bursts KW - Ultra-high energy cosmic rays KW - Radiation belts KW - Space mission Y1 - 2017 U6 - https://doi.org/10.1007/s11214-017-0425-x SN - 0038-6308 SN - 1572-9672 VL - 212 SP - 1705 EP - 1738 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Sun, Ning-Chen A1 - de Grijs, Richard A1 - Subramanian, Smitha A1 - Bekki, Kenji A1 - Bell, Cameron P. M. A1 - Cioni, Maria-Rosa L. A1 - Ivanov, Valentin D. A1 - Marconi, Marcella A1 - Oliveira, Joana M. A1 - Piatti, Andres E. A1 - Ripepi, Vincenzo A1 - Rubele, Stefano A1 - Tatton, Ben L. A1 - van Loon, Jacco Th. T1 - The VMC Survey. XXII. Hierarchical Star Formation in the 30 Doradus-N158–N159–N160 Star-forming Complex JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - Star formation is a hierarchical process, forming young stellar structures of star clusters, associations, and complexes over a wide range of scales. The star-forming complex in the bar region of the Large Magellanic Cloud is investigated with upper main-sequence stars observed by the VISTA Survey of the Magellanic Clouds. The upper main-sequence stars exhibit highly nonuniform distributions. Young stellar structures inside the complex are identified from the stellar density map as density enhancements of different significance levels. We find that these structures are hierarchically organized such that larger, lower-density structures contain one or several smaller, higher-density ones. They follow power-law size and mass distributions, as well as a lognormal surface density distribution. All these results support a scenario of hierarchical star formation regulated by turbulence. The temporal evolution of young stellar structures is explored by using subsamples of upper main-sequence stars with different magnitude and age ranges. While the youngest subsample, with a median age of log(tau/yr) = 7.2, contains the most substructure, progressively older ones are less and less substructured. The oldest subsample, with a median age of log(tau/yr) = 8.0, is almost indistinguishable from a uniform distribution on spatial scales of 30-300. pc, suggesting that the young stellar structures are completely dispersed on a timescale of similar to 100. Myr. These results are consistent with the characteristics of the 30. Doradus complex and the entire Large Magellanic Cloud, suggesting no significant environmental effects. We further point out that the fractal dimension may be method dependent for stellar samples with significant age spreads. KW - infrared: stars KW - Magellanic Clouds KW - stars: formation Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/aa911e SN - 0004-637X SN - 1538-4357 VL - 849 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Nidever, David L. A1 - Olsen, Knut A1 - Walker, Alistair R. A1 - Katherina Vivas, A. A1 - Blum, Robert D. A1 - Kaleida, Catherine A1 - Choi, Yumi A1 - Conn, Blair C. A1 - Gruendl, Robert A. A1 - Bell, Eric F. A1 - Besla, Gurtina A1 - Munoz, Ricardo R. A1 - Gallart, Carme A1 - Martin, Nicolas F. A1 - Olszewski, Edward W. A1 - Saha, Abhijit A1 - Monachesi, Antonela A1 - Monelli, Matteo A1 - de Boer, Thomas J. L. A1 - Johnson, L. Clifton A1 - Zaritsky, Dennis A1 - Stringfellow, Guy S. A1 - van der Marel, Roeland P. A1 - Cioni, Maria-Rosa L. A1 - Jin, Shoko A1 - Majewski, Steven R. A1 - Martinez-Delgado, David A1 - Monteagudo, Lara A1 - Noel, Noelia E. D. A1 - Bernard, Edouard J. A1 - Kunder, Andrea A1 - Chu, You-Hua A1 - Bell, Cameron P. M. A1 - Santana, Felipe A1 - Frechem, Joshua A1 - Medina, Gustavo E. A1 - Parkash, Vaishali A1 - Seron Navarrete, J. C. A1 - Hayes, Christian T1 - SMASH: Survey of the MAgellanic Stellar History JF - The astronomical journal N2 - The Large and Small Magellanic Clouds are unique local laboratories for studying the formation and evolution of small galaxies in exquisite detail. The Survey of the MAgellanic Stellar History (SMASH) is an NOAO community Dark Energy Camera (DECam) survey of the Clouds mapping 480 deg2 (distributed over similar to 2400 square degrees at similar to 20% filling factor) to similar to 24th. mag in ugriz. The primary goals of SMASH are to identify low surface brightness stellar populations associated with the stellar halos and tidal debris of the Clouds, and to derive spatially resolved star formation histories. Here, we present a summary of the survey, its data reduction, and a description of the first public Data Release (DR1). The SMASH DECam data have been reduced with a combination of the NOAO Community Pipeline, the PHOTRED automated point-spread-function photometry pipeline, and custom calibration software. The astrometric precision is similar to 15 mas and the accuracy is similar to 2 mas with respect to the Gaia reference frame. The photometric precision is similar to 0.5%-0.7% in griz and similar to 1% in u with a calibration accuracy of similar to 1.3% in all bands. The median 5s point source depths in ugriz are 23.9, 24.8, 24.5, 24.2, and 23.5 mag. The SMASH data have already been used to discover the Hydra II Milky Way satellite, the SMASH 1 old globular cluster likely associated with the LMC, and extended stellar populations around the LMC out to R. similar to. 18.4 kpc. SMASH DR1 contains measurements of similar to 100 million objects distributed in 61 fields. A prototype version of the NOAO Data Lab provides data access and exploration tools. KW - galaxies: dwarf KW - galaxies: individual (Large Magellanic Cloud, Small Magellanic Cloud) KW - Local Group KW - Magellanic Clouds KW - surveys Y1 - 2017 U6 - https://doi.org/10.3847/1538-3881/aa8d1c SN - 0004-6256 SN - 1538-3881 VL - 154 SP - 310 EP - 326 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Subramanian, Smitha A1 - Rubele, Stefano A1 - Sun, Ning-Chen A1 - Girardi, Leo A1 - de Grijs, Richard A1 - van Loon, Jacco Th. A1 - Cioni, Maria-Rosa L. A1 - Piatti, Andres E. A1 - Bekki, Kenji A1 - Emerson, Jim A1 - Ivanov, Valentin D. A1 - Kerber, Leandro A1 - Marconi, Marcella A1 - Ripepi, Vincenzo A1 - Tatton, Benjamin L. T1 - The VMC Survey - XXIV. Signatures of tidally stripped stellar populations from the inner Small Magellanic Cloud JF - Monthly notices of the Royal Astronomical Society KW - stars: individual: red clump stars KW - galaxies: interactions KW - Magellanic Clouds Y1 - 2017 U6 - https://doi.org/10.1093/mnras/stx205 SN - 0035-8711 SN - 1365-2966 VL - 467 SP - 2980 EP - 2995 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Sander, Mathias A1 - Herzog, Marc A1 - Pudell, Jan-Etienne A1 - Bargheer, Matias A1 - Weinkauf, N. A1 - Pedersen, M. A1 - Newby, G. A1 - Sellmann, J. A1 - Schwarzkopf, J. A1 - Besse, V. A1 - Temnov, V. V. A1 - Gaal, P. T1 - Spatiotemporal Coherent Control of Thermal Excitations in Solids JF - Physical review letters N2 - X-ray reflectivity measurements of femtosecond laser-induced transient gratings (TG) are applied to demonstrate the spatiotemporal coherent control of thermally induced surface deformations on ultrafast time scales. Using grazing incidence x-ray diffraction we unambiguously measure the amplitude of transient surface deformations with sub-angstrom resolution. Understanding the dynamics of femtosecond TG excitations in terms of superposition of acoustic and thermal gratings makes it possible to develop new ways of coherent control in x-ray diffraction experiments. Being the dominant source of TG signal, the long-living thermal grating with spatial period. can be canceled by a second, time-delayed TG excitation shifted by Lambda/2. The ultimate speed limits of such an ultrafast x-ray shutter are inferred from the detailed analysis of thermal and acoustic dynamics in TG experiments. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevLett.119.075901 SN - 0031-9007 SN - 1079-7114 VL - 119 SP - 102 EP - 110 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Sander, Mathias A1 - Pudell, Jan-Etienne A1 - Herzog, Marc A1 - Bargheer, Matias A1 - Bauer, R. A1 - Besse, V. A1 - Temnov, V. A1 - Gaal, P. T1 - Quantitative disentanglement of coherent and incoherent laser-induced surface deformations by time-resolved x-ray reflectivity JF - Applied physics letters N2 - We present time-resolved x-ray reflectivity measurements on laser excited coherent and incoherent surface deformations of thin metallic films. Based on a kinematical diffraction model, we derive the surface amplitude from the diffracted x-ray intensity and resolve transient surface excursions with sub-angstrom spatial precision and 70 ps temporal resolution. The analysis allows for decomposition of the surface amplitude into multiple coherent acoustic modes and a substantial contribution from incoherent phonons which constitute the sample heating. Published by AIP Publishing. Y1 - 2017 U6 - https://doi.org/10.1063/1.5004522 SN - 0003-6951 SN - 1077-3118 VL - 111 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Roland, Steffen A1 - Yan, Liang A1 - Zhang, Qianqian A1 - Jiao, Xuechen A1 - Hunt, Adrian A1 - Ghasemi, Masoud A1 - Ade, Harald A1 - You, Wei A1 - Neher, Dieter T1 - Charge Generation and Mobility-Limited Performance of Bulk Heterojunction Solar Cells with a Higher Adduct Fullerene JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Alternative electron acceptors are being actively explored in order to advance the development of bulk-heterojunction (BHJ) organic solar cells (OSCs). The indene-C-60 bisadduct (ICBA) has been regarded as a promising candidate, as it provides high open-circuit voltage in BHJ solar cells; however, the photovoltaic performance of such ICBA-based devices is often inferior when compared to cells with the omnipresent PCBM electron acceptor. Here, by pairing the high performance polymer (FTAZ) as the donor with either PCBM or ICBA as the acceptor, we explore the physical mechanism behind the reduced performance of the ICBA-based device. Time delayed collection field (TDCF) experiments reveal reduced, yet field-independent free charge generation in the FTAZ:ICBA system, explaining the overall lower photocurrent in its cells. Through the analysis of the photoluminescence, photogeneration, and electroluminescence, we find that the lower generation efficiency is neither caused by inefficient exciton splitting, nor do we find evidence for significant energy back-transfer from the CT state to singlet excitons. In fact, the increase in open circuit voltage when replacing PCBM by ICBA is entirely caused by the increase in the CT energy, related to the shift in the LUMO energy, while changes in the radiative and nonradiative recombination losses are nearly absent. On the other hand, space charge limited current (SCLC) and bias-assisted charge extraction (BACE) measurements consistently reveal a severely lower electron mobilitiy in the FTAZ:ICBA blend. Studies of the blends with resonant soft X-ray scattering (R-SoXS), grazing incident wide-angle X-ray scattering (GIWAXS), and scanning transmission X-ray microscopy (STXM) reveal very little differences in the mesoscopic morphology but significantly less nanoscale molecular ordering of the fullerene domains in the ICBA based blends, which we propose as the main cause for the lower generation efficiency and smaller electron mobility. Calculations of the JV curves with an analytical model, using measured values, show good agreement with the experimentally determined JV characteristics, proving that these devices suffer from slow carrier extraction, resulting in significant bimolecular recombination losses. Therefore, this study highlights the importance of high charge carrier mobility for newly synthesized acceptor materials, in addition to having suitable energy levels. Y1 - 2017 U6 - https://doi.org/10.1021/acs.jpcc.7b02288 SN - 1932-7447 VL - 121 SP - 10305 EP - 10316 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Benduhn, Johannes A1 - Tvingstedt, Kristofer A1 - Piersimoni, Fortunato A1 - Ullbrich, Sascha A1 - Fan, Yeli A1 - Tropiano, Manuel A1 - McGarry, Kathryn A. A1 - Zeika, Olaf A1 - Riede, Moritz K. A1 - Douglas, Christopher J. A1 - Barlow, Stephen A1 - Marder, Seth R. A1 - Neher, Dieter A1 - Spoltore, Donato A1 - Vandewal, Koen T1 - Intrinsic non-radiative voltage losses in fullerene-based organic solar cells JF - Nature Energy N2 - Organic solar cells demonstrate external quantum efficiencies and fill factors approaching those of conventional photovoltaic technologies. However, as compared with the optical gap of the absorber materials, their open-circuit voltage is much lower, largely due to the presence of significant non-radiative recombination. Here, we study a large data set of published and new material combinations and find that non-radiative voltage losses decrease with increasing charge-transfer-state energies. This observation is explained by considering non-radiative charge-transfer-state decay as electron transfer in the Marcus inverted regime, being facilitated by a common skeletal molecular vibrational mode. Our results suggest an intrinsic link between non-radiative voltage losses and electron-vibration coupling, indicating that these losses are unavoidable. Accordingly, the theoretical upper limit for the power conversion efficiency of single-junction organic solar cells would be reduced to about 25.5% and the optimal optical gap increases to (1.45-1.65) eV, that is, (0.2-0.3) eV higher than for technologies with minimized non-radiative voltage losses. Y1 - 2017 U6 - https://doi.org/10.1038/nenergy.2017.53 SN - 2058-7546 VL - 2 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Hofacker, Andreas A1 - Neher, Dieter T1 - Dispersive and steady-state recombination in organic disordered semiconductors JF - Physical review : B, Condensed matter and materials physics N2 - Charge carrier recombination in organic disordered semiconductors is strongly influenced by the thermalization of charge carriers in the density of states (DOS). Measurements of recombination dynamics, conducted under transient or steady-state conditions, can easily be misinterpreted when a detailed understanding of the interplay of thermalization and recombination is missing. To enable adequate measurement analysis, we solve the multiple-trapping problem for recombining charge carriers and analyze it in the transient and steady excitation paradigm for different DOS distributions. We show that recombination rates measured after pulsed excitation are inherently time dependent since recombination gradually slows down as carriers relax in the DOS. When measuring the recombination order after pulsed excitation, this leads to an apparent high-order recombination at short times. As times goes on, the recombination order approaches an asymptotic value. For the Gaussian and the exponential DOS distributions, this asymptotic value equals the recombination order of the equilibrated system under steady excitation. For a more general DOS distribution, the recombination order can also depend on the carrier density, under both transient and steady-state conditions. We conclude that transient experiments can provide rich information about recombination in and out of equilibrium and the underlying DOS occupation provided that consistent modeling of the system is performed. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevB.96.245204 SN - 2469-9950 SN - 2469-9969 VL - 96 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Collado-Fregoso, Elisa A1 - Hood, Samantha N. A1 - Shoaee, Safa A1 - Schröder, Bob C. A1 - McCulloch, Iain A1 - Kassal, Ivan A1 - Neher, Dieter A1 - Durrant, James R. T1 - Intercalated vs Nonintercalated Morphologies in Donor-Acceptor Bulk Heterojunction Solar Cells: PBTTT:Fullerene Charge Generation and Recombination Revisited JF - The journal of physical chemistry letters N2 - In this Letter, we study the role of the donor:acceptor interface nanostructure upon charge separation and recombination in organic photovoltaic devices and blend films, using mixtures of PBTTT and two different fullerene derivatives (PC70BM and ICTA) as models for intercalated and nonintercalated morphologies, respectively. Thermodynamic simulations show that while the completely intercalated system exhibits a large free-energy barrier for charge separation, this barrier is significantly lower in the nonintercalated system and almost vanishes when energetic disorder is included in the model. Despite these differences, both femtosecond-resolved transient absorption spectroscopy (TAS) and time-delayed collection field (TDCF) exhibit extensive first-order losses in both systems, suggesting that geminate pairs are the primary product of photoexcitation. In contrast, the system that comprises a combination of fully intercalated polymer:fullerene areas and fullerene-aggregated domains (1:4 PBTTT:PC70BM) is the only one that shows slow, second-order recombination of free charges, resulting in devices with an overall higher short-circuit current and fill factor. This study therefore provides a novel consideration of the role of the interfacial nanostructure and the nature of bound charges and their impact upon charge generation and recombination. Y1 - 2017 U6 - https://doi.org/10.1021/acs.jpclett.7b01571 SN - 1948-7185 VL - 8 SP - 4061 EP - 4068 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Nikolis, Vasileios C. A1 - Benduhn, Johannes A1 - Holzmueller, Felix A1 - Piersimoni, Fortunato A1 - Lau, Matthias A1 - Zeika, Olaf A1 - Neher, Dieter A1 - Koerner, Christian A1 - Spoltore, Donato A1 - Vandewal, Koen T1 - Reducing Voltage Losses in Cascade Organic Solar Cells while Maintaining High External Quantum Efficiencies JF - dvanced energy materials N2 - High photon energy losses limit the open-circuit voltage (V-OC) and power conversion efficiency of organic solar cells (OSCs). In this work, an optimization route is presented which increases the V-OC by reducing the interfacial area between donor (D) and acceptor (A). This optimization route concerns a cascade device architecture in which the introduction of discontinuous interlayers between alpha-sexithiophene (alpha-6T) (D) and chloroboron subnaphthalocyanine (SubNc) (A) increases the V-OC of an alpha-6T/SubNc/SubPc fullerene-free cascade OSC from 0.98 V to 1.16 V. This increase of 0.18 V is attributed solely to the suppression of nonradiative recombination at the D-A interface. By accurately measuring the optical gap (E-opt) and the energy of the charge-transfer state (E-CT) of the studied OSC, a detailed analysis of the overall voltage losses is performed. E-opt - qV(OC) losses of 0.58 eV, which are among the lowest observed for OSCs, are obtained. Most importantly, for the V-OC-optimized devices, the low-energy (700 nm) external quantum efficiency (EQE) peak remains high at 79%, despite a minimal driving force for charge separation of less than 10 meV. This work shows that low-voltage losses can be combined with a high EQE in organic photovoltaic devices. KW - energy losses KW - nonradiative recombination KW - open-circuit voltage KW - organic solar cells KW - voltage losses Y1 - 2017 U6 - https://doi.org/10.1002/aenm.201700855 SN - 1614-6832 SN - 1614-6840 VL - 7 SP - 122 EP - 136 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Hofacker, Andreas A1 - Neher, Dieter T1 - Dispersive and steady-state recombination in organic disordered semiconductors JF - Physical review : B, Condensed matter and materials physics N2 - Charge carrier recombination in organic disordered semiconductors is strongly influenced by the thermalization of charge carriers in the density of states (DOS). Measurements of recombination dynamics, conducted under transient or steady-state conditions, can easily be misinterpreted when a detailed understanding of the interplay of thermalization and recombination is missing. To enable adequate measurement analysis, we solve the multiple-trapping problem for recombining charge carriers and analyze it in the transient and steady excitation paradigm for different DOS distributions. We show that recombination rates measured after pulsed excitation are inherently time dependent since recombination gradually slows down as carriers relax in the DOS. When measuring the recombination order after pulsed excitation, this leads to an apparent high-order recombination at short times. As times goes on, the recombination order approaches an asymptotic value. For the Gaussian and the exponential DOS distributions, this asymptotic value equals the recombination order of the equilibrated system under steady excitation. For a more general DOS distribution, the recombination order can also depend on the carrier density, under both transient and steady-state conditions. We conclude that transient experiments can provide rich information about recombination in and out of equilibrium and the underlying DOS occupation provided that consistent modeling of the system is performed. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevB.96.245204 SN - 2469-9950 SN - 2469-9969 VL - 96 SP - 5640 EP - 5649 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Cao, Xing A1 - Shprits, Yuri Y. A1 - Ni, Binbin A1 - Zhelavskaya, Irina T1 - Scattering of Ultra-relativistic Electrons in the Van Allen Radiation Belts Accounting for Hot Plasma Effects JF - Scientific reports N2 - Electron flux in the Earth’s outer radiation belt is highly variable due to a delicate balance between competing acceleration and loss processes. It has been long recognized that Electromagnetic Ion Cyclotron (EMIC) waves may play a crucial role in the loss of radiation belt electrons. Previous theoretical studies proposed that EMIC waves may account for the loss of the relativistic electron population. However, recent observations showed that while EMIC waves are responsible for the significant loss of ultra-relativistic electrons, the relativistic electron population is almost unaffected. In this study, we provide a theoretical explanation for this discrepancy between previous theoretical studies and recent observations. We demonstrate that EMIC waves mainly contribute to the loss of ultra-relativistic electrons. This study significantly improves the current understanding of the electron dynamics in the Earth’s radiation belt and also can help us understand the radiation environments of the exoplanets and outer planets. Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-17739-7 SN - 2045-2322 VL - 7 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Usanova, Maria E. A1 - Shprits, Yuri Y. T1 - Inner magnetosphere coupling BT - Recent advances JF - Journal of geophysical research : Space physics N2 - The dynamics of the inner magnetosphere is strongly governed by the interactions between different plasma populations that are coupled through large-scale electric and magnetic fields, currents, and wave-particle interactions. Inner magnetospheric plasma undergoes self-consistent interactions with global electric and magnetic fields. Waves excited in the inner magnetosphere from unstable particle distributions can provide energy exchange between different particle populations in the inner magnetosphere and affect the ring current and radiation belt dynamics. The ionosphere serves as an energy sink and feeds the magnetosphere back through the cold plasma outflow. The precipitating inner magnetospheric particles influence the ionosphere and upper atmospheric chemistry and affect climate. Satellite measurements and theoretical studies have advanced our understanding of the dynamics of various plasma populations in the inner magnetosphere. However, our knowledge of the coupling processes among the plasmasphere, ring current, radiation belts, global magnetic and electric fields, and plasma waves generated within these systems is still incomplete. This special issue incorporates extended papers presented at the Inner Magnetosphere Coupling III conference held 23–27 March 2015 in Los Angeles, California, USA, and includes modeling and observational contributions addressing interactions within different plasma populations in the inner magnetosphere (plasmasphere, ring current, and radiation belts), coupling between fields and plasma populations, as well as effects of the inner magnetosphere on the ionosphere and atmosphere. KW - inner magnetosphere KW - ring current KW - radiation belts KW - magnetosphere KW - ionosphere interactions KW - plasmasphere KW - solar wind Y1 - 2016 U6 - https://doi.org/10.1002/2016JA023614 SN - 2169-9380 SN - 2169-9402 VL - 122 IS - 1 SP - 102 EP - 104 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Zhelavskaya, Irina A1 - Shprits, Yuri Y. A1 - Spasojevic, Maria T1 - Empirical Modeling of the Plasmasphere Dynamics Using Neural Networks JF - Journal of geophysical research : Space physics N2 - We present the PINE (Plasma density in the Inner magnetosphere Neural network‐based Empirical) model ‐ a new empirical model for reconstructing the global dynamics of the cold plasma density distribution based only on solar wind data and geomagnetic indices. Utilizing the density database obtained using the NURD (Neural‐network‐based Upper hybrid Resonance Determination) algorithm for the period of 1 October 2012 to 1 July 2016, in conjunction with solar wind data and geomagnetic indices, we develop a neural network model that is capable of globally reconstructing the dynamics of the cold plasma density distribution for 2≤L≤6 and all local times. We validate and test the model by measuring its performance on independent data sets withheld from the training set and by comparing the model‐predicted global evolution with global images of He+ distribution in the Earth's plasmasphere from the IMAGE Extreme UltraViolet (EUV) instrument. We identify the parameters that best quantify the plasmasphere dynamics by training and comparing multiple neural networks with different combinations of input parameters (geomagnetic indices, solar wind data, and different durations of their time history). The optimal model is based on the 96 h time history of Kp, AE, SYM‐H, and F10.7 indices. The model successfully reproduces erosion of the plasmasphere on the nightside and plume formation and evolution. We demonstrate results of both local and global plasma density reconstruction. This study illustrates how global dynamics can be reconstructed from local in situ observations by using machine learning techniques. Y1 - 2017 U6 - https://doi.org/10.1002/2017JA024406 SN - 2169-9380 SN - 2169-9402 VL - 122 SP - 11227 EP - 11244 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Fondell, Mattis A1 - Eckert, Sebastian A1 - Jay, Raphael Martin A1 - Weniger, Christian A1 - Quevedo, Wilson A1 - Niskanen, Johannes A1 - Kennedy, Brian A1 - Sorgenfrei, Nomi A1 - Schick, Daniel A1 - Giangrisostomi, Erika A1 - Ovsyannikov, Ruslan A1 - Adamczyk, Katrin A1 - Huse, Nils A1 - Wernet, Philippe A1 - Mitzner, Rolf A1 - Föhlisch, Alexander T1 - Time-resolved soft X-ray absorption spectroscopy in transmission mode on liquids at MHz repetition rates JF - Structural dynamics N2 - We present a setup combining a liquid flatjet sample delivery and a MHz laser system for time-resolved soft X-ray absorption measurements of liquid samples at the high brilliance undulator beamline UE52-SGM at Bessy II yielding unprecedented statistics in this spectral range. We demonstrate that the efficient detection of transient absorption changes in transmission mode enables the identification of photoexcited species in dilute samples. With iron(II)-trisbipyridine in aqueous solution as a benchmark system, we present absorption measurements at various edges in the soft X-ray regime. In combination with the wavelength tunability of the laser system, the set-up opens up opportunities to study the photochemistry of many systems at low concentrations, relevant to materials sciences, chemistry, and biology. (C) 2017 Author(s). Y1 - 2017 U6 - https://doi.org/10.1063/1.4993755 SN - 2329-7778 VL - 4 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Kim, Kyung-Chan A1 - Shprits, Yuri Y. T1 - Dependence of the amplitude of magnetosonic waves on the solar wind and AE index using Van Allen Probes JF - Journal of geophysical research : Space physics N2 - We present the dependence of the magnetosonic wave amplitudes both outside and inside the plasmapause on the solar wind and AE index using Van Allen Probe-A spacecraft during the time period of 1 October 2012 to 31 December 2015, based on a correlation and regression analysis. Solar wind parameters considered are the southward interplanetary magnetic field (IMF B-S), solar wind number density (N-SW), and bulk speed (V-SW). We find that the wave amplitudes outside (inside) the plasmapause are well correlated with the preceding AE, IMF B-S, and N-SW with time delays, each corresponding to 2-3 h (3-4 h), 4-5 h (3-4 h), and 2-3 h (8-9 h), while the correlation with V-SW is ambiguous both inside and outside the plasmapause. As measured by the correlation coefficient, the IMF B-S is the most influential solar wind parameter that affects the dayside wave amplitudes both outside and inside the plasmapause, while N-SW contributes to enhancing the duskside waves outside the plasmapause. The AE effect on wave amplitudes is comparable to that of IMF B-S. More interestingly, regression with time histories of the solar wind parameters and the AE index preceding the wave measurements outside the plasmapause shows significant dependence on the IMF B-S, N-SW, and AE: the region of peak coefficients is changed with time delay for IMF B-S and AE, while isolated peaks around duskside remain gradually decrease with time for N-SW. In addition, the regression with magnetosonic waves inside the plasmapause shows high coefficients around prenoon sector with preceding IMF B-S and V-SW. KW - magnetosonic equatorial noise KW - solar wind dependence KW - Van Allen Probes Y1 - 2017 U6 - https://doi.org/10.1002/2017JA024094 SN - 2169-9380 SN - 2169-9402 VL - 122 SP - 6022 EP - 6034 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Drozdov, Alexander A1 - Shprits, Yuri Y. A1 - Usanova, Maria E. A1 - Aseev, Nikita A1 - Kellerman, Adam C. A1 - Zhu, H. T1 - EMIC wave parameterization in the long-term VERB code simulation JF - Journal of geophysical research : Space physics N2 - Electromagnetic ion cyclotron (EMIC) waves play an important role in the dynamics of ultrarelativistic electron population in the radiation belts. However, as EMIC waves are very sporadic, developing a parameterization of such wave properties is a challenging task. Currently, there are no dynamic, activity-dependent models of EMIC waves that can be used in the long-term (several months) simulations, which makes the quantitative modeling of the radiation belt dynamics incomplete. In this study, we investigate Kp, Dst, and AE indices, solar wind speed, and dynamic pressure as possible parameters of EMIC wave presence. The EMIC waves are included in the long-term simulations (1year, including different geomagnetic activity) performed with the Versatile Electron Radiation Belt code, and we compare results of the simulation with the Van Allen Probes observations. The comparison shows that modeling with EMIC waves, parameterized by solar wind dynamic pressure, provides a better agreement with the observations among considered parameterizations. The simulation with EMIC waves improves the dynamics of ultrarelativistic fluxes and reproduces the formation of the local minimum in the phase space density profiles. KW - radiation belts KW - VERB code KW - EMIC Y1 - 2017 U6 - https://doi.org/10.1002/2017JA024389 SN - 2169-9380 SN - 2169-9402 VL - 122 SP - 8488 EP - 8501 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Aseev, Nikita A1 - Shprits, Yuri Y. A1 - Drozdov, Alexander A1 - Kellerman, Adam C. A1 - Usanova, Maria E. A1 - Wang, D. A1 - Zhelavskaya, Irina T1 - Signatures of Ultrarelativistic Electron Loss in the Heart of the Outer Radiation Belt Measured by Van Allen Probes JF - Journal of geophysical research : Space physics N2 - Up until recently, signatures of the ultrarelativistic electron loss driven by electromagnetic ion cyclotron (EMIC) waves in the Earth's outer radiation belt have been limited to direct or indirect measurements of electron precipitation or the narrowing of normalized pitch angle distributions in the heart of the belt. In this study, we demonstrate additional observational evidence of ultrarelativistic electron loss that can be driven by resonant interaction with EMIC waves. We analyzed the profiles derived from Van Allen Probe particle data as a function of time and three adiabatic invariants between 9 October and 29 November 2012. New local minimums in the profiles are accompanied by the narrowing of normalized pitch angle distributions and ground‐based detection of EMIC waves. Such a correlation may be indicative of ultrarelativistic electron precipitation into the Earth's atmosphere caused by resonance with EMIC waves. Y1 - 2017 U6 - https://doi.org/10.1002/2017JA024485 SN - 2169-9380 SN - 2169-9402 VL - 122 SP - 10102 EP - 10111 PB - American Geophysical Union CY - Washington ER - TY - GEN A1 - Shprits, Yuri Y. T1 - Editorial: Topical Collection on the Lomonosov Mission T2 - Space science reviews Y1 - 2017 U6 - https://doi.org/10.1007/s11214-017-0393-1 SN - 0038-6308 SN - 1572-9672 VL - 212 SP - 1685 EP - 1686 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Shprits, Yuri Y. A1 - Angelopoulos, V. A1 - Russell, C. T. A1 - Strangeway, R. J. A1 - Runov, A. A1 - Turner, D. A1 - Caron, R. A1 - Cruce, P. A1 - Leneman, D. A1 - Michaelis, I. A1 - Petrov, V. A1 - Panasyuk, M. A1 - Yashin, I. A1 - Drozdov, Alexander A1 - Russell, C. L. A1 - Kalegaev, V. A1 - Nazarkov, I. A1 - Clemmons, J. H. T1 - Scientific Objectives of Electron Losses and Fields INvestigation Onboard Lomonosov Satellite JF - Space science reviews N2 - 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. KW - Magnetospheric physics KW - Observations KW - Particles precipitating KW - Particles trapped KW - Radiation belts Y1 - 2017 U6 - https://doi.org/10.1007/s11214-017-0455-4 SN - 0038-6308 SN - 1572-9672 VL - 214 IS - 1 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Shprits, Yuri Y. A1 - Kellerman, Adam C . A1 - Aseev, Nikita A1 - Drozdov, Alexander A1 - Michaelis, Ingo T1 - Multi-MeV electron loss in the heart of the radiation belts JF - Geophysical research letters N2 - Significant progress has been made in recent years in understanding acceleration mechanisms in the Earth's radiation belts. In particular, a number of studies demonstrated the importance of the local acceleration by analyzing the radial profiles of phase space density (PSD) and observing building up peaks in PSD. In this study, we focus on understanding of the local loss using very similar tools. The profiles of PSD for various values of the first adiabatic invariants during the previously studied 17 January 2013 storm are presented and discussed. The profiles of PSD show clear deepening minimums consistent with the scattering by electromagnetic ion cyclotron waves. Long-term evolution shows that local minimums in PSD can persist for relatively long times. During considered interval of time the deepening minimums were observed around L* = 4 during 17 January 2013 storm and around L* = 3.5 during 1 March 2013 storm. This study shows a new method that can help identify the location, magnitude, and time of the local loss and will help quantify local loss in the future. This study also provides additional clear and definitive evidence that local loss plays a major role for the dynamics of the multi-MeV electrons. Y1 - 2017 U6 - https://doi.org/10.1002/2016GL072258 SN - 0094-8276 SN - 1944-8007 VL - 44 IS - 3 SP - 1204 EP - 1209 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Kwamen, C. A1 - Rössle, Matthias A1 - Reinhardt, M. A1 - Leitenberger, Wolfram A1 - Zamponi, Flavio A1 - Alexe, Marin A1 - Bargheer, Matias T1 - Simultaneous dynamic characterization of charge and structural motion during ferroelectric switching JF - Physical review : B, Condensed matter and materials physics N2 - Monitoring structural changes in ferroelectric thin films during electric field induced polarization switching is important for a full microscopic understanding of the coupled motion of charges, atoms, and domainwalls in ferroelectric nanostructures. We combine standard ferroelectric test sequences of switching and nonswitching electrical pulses with time-resolved x-ray diffraction to investigate the structural response of a nanoscale Pb(Zr0.2Ti0.8)O-3 ferroelectric oxide capacitor upon charging, discharging, and polarization reversal. We observe that a nonlinear piezoelectric response of the ferroelectric layer develops on a much longer time scale than the RC time constant of the device. The complex atomic motion during the ferroelectric polarization reversal starts with a contraction of the lattice, whereas the expansive piezoelectric response sets in after considerable charge flow due to the applied voltage pulses on the electrodes of the capacitor. Our simultaneous measurements on a working device elucidate and visualize the complex interplay of charge flow and structural motion and challenges theoretical modeling. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevB.96.134105 SN - 2469-9950 SN - 2469-9969 VL - 96 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Lomadze, Nino A1 - Kopyshev, Alexey A1 - Bargheer, Matias A1 - Wollgarten, Markus A1 - Santer, Svetlana T1 - Mass production of polymer nano-wires filled with metal nano-particles JF - Scientific reports N2 - Despite the ongoing progress in nanotechnology and its applications, the development of strategies for connecting nano-scale systems to micro-or macroscale elements is hampered by the lack of structural components that have both, nano-and macroscale dimensions. The production of nano-scale wires with macroscale length is one of the most interesting challenges here. There are a lot of strategies to fabricate long nanoscopic stripes made of metals, polymers or ceramics but none is suitable for mass production of ordered and dense arrangements of wires at large numbers. In this paper, we report on a technique for producing arrays of ordered, flexible and free-standing polymer nano-wires filled with different types of nano-particles. The process utilizes the strong response of photosensitive polymer brushes to irradiation with UV-interference patterns, resulting in a substantial mass redistribution of the polymer material along with local rupturing of polymer chains. The chains can wind up in wires of nano-scale thickness and a length of up to several centimeters. When dispersing nano-particles within the film, the final arrangement is similar to a core-shell geometry with mainly nano-particles found in the core region and the polymer forming a dielectric jacket. Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-08153-0 SN - 2045-2322 VL - 7 SP - 3759 EP - 3764 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Lomadze, Nino A1 - Kopyshev, Alexey A1 - Bargheer, Matias A1 - Wollgarten, Markus A1 - Santer, Svetlana T1 - Mass production of polymer nanowires filled with metal nanoparticles JF - Scientific reports N2 - Despite the ongoing progress in nanotechnology and its applications, the development of strategies for connecting nano-scale systems to micro- or macroscale elements is hampered by the lack of structural components that have both, nano- and macroscale dimensions. The production of nano-scale wires with macroscale length is one of the most interesting challenges here. There are a lot of strategies to fabricate long nanoscopic stripes made of metals, polymers or ceramics but none is suitable for mass production of ordered and dense arrangements of wires at large numbers. In this paper, we report on a technique for producing arrays of ordered, flexible and free-standing polymer nano-wires filled with different types of nano-particles. The process utilizes the strong response of photosensitive polymer brushes to irradiation with UV-interference patterns, resulting in a substantial mass redistribution of the polymer material along with local rupturing of polymer chains. The chains can wind up in wires of nano-scale thickness and a length of up to several centimeters. When dispersing nano-particles within the film, the final arrangement is similar to a core-shell geometry with mainly nano-particles found in the core region and the polymer forming a dielectric jacket. Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-08153-0 SN - 2045-2322 VL - 7 PB - Springer Nature CY - London ER - TY - JOUR A1 - El-Nagar, Gumaa A. A1 - Sarhan, Radwan Mohamed A1 - Abouserie, Ahed A1 - Maticiuc, Natalia A1 - Bargheer, Matias A1 - Lauermann, Iver A1 - Roth, Christina T1 - Efficient 3D-Silver Flower-like Microstructures for Non-Enzymatic Hydrogen Peroxide (H2O2) Amperometric Detection JF - Scientific reports Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-11965-9 SN - 2045-2322 VL - 7 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Wolff, Christian Michael A1 - Zu, Fengshuo A1 - Paulke, Andreas A1 - Perdigón-Toro, Lorena A1 - Koch, Norbert A1 - Neher, Dieter T1 - Reduced Interface-Mediated Recombination for High Open-Circuit Voltages in CH3NH3PbI3 Solar Cells JF - Advanced materials N2 - Perovskite solar cells with all-organic transport layers exhibit efficiencies rivaling their counterparts that employ inorganic transport layers, while avoiding high-temperature processing. Herein, it is investigated how the choice of the fullerene derivative employed in the electron-transporting layer of inverted perovskite cells affects the open-circuit voltage (V-OC). It is shown that nonradiative recombination mediated by the electron-transporting layer is the limiting factor for the V-OC in the cells. By inserting an ultrathin layer of an insulating polymer between the active CH3NH3PbI3 perovskite and the fullerene, an external radiative efficiency of up to 0.3%, a V-OC as high as 1.16 V, and a power conversion efficiency of 19.4% are realized. The results show that the reduction of nonradiative recombination due to charge-blocking at the perovskite/organic interface is more important than proper level alignment in the search for ideal selective contacts toward high V-OC and efficiency. KW - electron-transport layers KW - nonradiative recombination KW - open-circuit voltage KW - perovskite solar cells Y1 - 2017 U6 - https://doi.org/10.1002/adma.201700159 SN - 0935-9648 SN - 1521-4095 VL - 29 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Stolterfoht, Martin A1 - Wolff, Christian Michael A1 - Amir, Yohai A1 - Paulke, Andreas A1 - Perdigón-Toro, Lorena A1 - Caprioglio, Pietro A1 - Neher, Dieter T1 - Approaching the fill factor Shockley-Queisser limit in stable, dopant-free triple cation perovskite solar cells JF - Energy & Environmental Science N2 - Perovskite solar cells now compete with their inorganic counterparts in terms of power conversion efficiency, not least because of their small open-circuit voltage (V-OC) losses. A key to surpass traditional thin-film solar cells is the fill factor (FF). Therefore, more insights into the physical mechanisms that define the bias dependence of the photocurrent are urgently required. In this work, we studied charge extraction and recombination in efficient triple cation perovskite solar cells with undoped organic electron/hole transport layers (ETL/HTL). Using integral time of flight we identify the transit time through the HTL as the key figure of merit for maximizing the fill factor (FF) and efficiency. Complementarily, intensity dependent photocurrent and V-OC measurements elucidate the role of the HTL on the bias dependence of non-radiative and transport-related loss channels. We show that charge transport losses can be completely avoided under certain conditions, yielding devices with FFs of up to 84%. Optimized cells exhibit power conversion efficiencies of above 20% for 6 mm(2) sized pixels and 18.9% for a device area of 1 cm(2). These are record efficiencies for hybrid perovskite devices with dopant-free transport layers, highlighting the potential of this device technology to avoid charge-transport limitations and to approach the Shockley-Queisser limit. Y1 - 2017 U6 - https://doi.org/10.1039/c7ee00899f SN - 1754-5692 SN - 1754-5706 VL - 10 SP - 1530 EP - 1539 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Abdalla, Hassan E. A1 - Abramowski, Attila A1 - Aharonian, Felix A. A1 - Benkhali, Faical Ait A1 - Akhperjanian, A. G. A1 - Andersson, T. A1 - Anguner, Ekrem Oǧuzhan A1 - Arakawa, M. A1 - Arrieta, M. A1 - Aubert, Pierre A1 - Backes, Michael A1 - Balzer, Arnim A1 - Barnard, Michelle A1 - Becherini, Yvonne A1 - Tjus, J. Becker A1 - Berge, David A1 - Bernhard, Sabrina A1 - Bernlöhr, K. A1 - Blackwell, R. A1 - Böttcher, Markus A1 - Boisson, Catherine A1 - Bolmont, J. A1 - Bonnefoy, S. A1 - Bordas, Pol A1 - Bregeon, Johan A1 - Brun, Francois A1 - Brun, Pierre A1 - Bryan, Mark A1 - Buechele, M. A1 - Bulik, Tomasz A1 - Capasso, M. A1 - Carr, John A1 - Casanova, Sabrina A1 - Cerruti, M. A1 - Chakraborty, N. A1 - Chaves, Ryan C. G. A1 - Chen, Andrew A1 - Chevalier, J. A1 - Coffaro, M. A1 - Colafrancesco, Sergio A1 - Cologna, Gabriele A1 - Condon, B. A1 - Conrad, Jan A1 - Cui, Y. A1 - Davids, I. D. A1 - Decock, J. A1 - Degrange, B. A1 - Deil, C. A1 - Devin, J. A1 - de Wilt, P. A1 - Dirson, L. A1 - Djannati-Atai, A. A1 - Domainko, W. A1 - Donath, A. A1 - Dutson, K. A1 - Dyks, J. A1 - Edwards, T. A1 - Egberts, Kathrin A1 - Eger, P. A1 - Ernenwein, J. -P. A1 - Eschbach, S. A1 - Farnier, C. A1 - Fegan, S. A1 - Fernandes, M. V. A1 - Fiasson, A. A1 - Fontaine, G. A1 - Foerster, A. A1 - Funk, S. A1 - Fuessling, M. A1 - Gabici, S. A1 - Gallant, Y. A. A1 - Garrigoux, T. A1 - Giavitto, G. A1 - Giebels, B. A1 - Glicenstein, J. F. A1 - Gottschall, D. A1 - Goyal, A. A1 - Grondin, M. -H. A1 - Hahn, J. A1 - Haupt, M. A1 - Hawkes, J. A1 - Heinzelmann, G. A1 - Henri, G. A1 - Hermann, G. A1 - Hinton, James Anthony A1 - Hofmann, W. A1 - Hoischen, Clemens A1 - Holch, Tim Lukas A1 - Holler, M. A1 - Horns, D. A1 - Ivascenko, A. A1 - Iwasaki, H. A1 - Jacholkowska, A. A1 - Jamrozy, M. A1 - Janiak, M. A1 - Jankowsky, D. A1 - Jankowsky, F. A1 - Jingo, M. A1 - Jogler, T. A1 - Jouvin, L. A1 - Jung-Richardt, I. A1 - Kastendieck, M. A. A1 - Katarzynski, K. A1 - Katsuragawa, M. A1 - Katz, U. A1 - Kerszberg, D. A1 - Khangulyan, D. A1 - Khelifi, B. A1 - King, J. A1 - Klepser, S. A1 - Klochkov, D. A1 - Kluzniak, W. A1 - Kolitzus, D. A1 - Komin, Nu. A1 - Kosack, K. A1 - Krakau, S. A1 - Kraus, M. A1 - Kruger, P. P. A1 - Laffon, H. A1 - Lamanna, G. A1 - Lau, J. A1 - Lees, J. -P. A1 - Lefaucheur, J. A1 - Lefranc, V. A1 - Lemiere, A. A1 - Lemoine-Goumard, M. A1 - Lenain, J. -P. A1 - Leser, Eva A1 - Lohse, T. A1 - Lorentz, M. A1 - Liu, R. A1 - Lopez-Coto, R. A1 - Lypova, I. A1 - Marandon, V. A1 - Marcowith, Alexandre A1 - Mariaud, C. A1 - Marx, R. A1 - Maurin, G. A1 - Maxted, N. A1 - Mayer, M. A1 - Meintjes, P. J. A1 - Meyer, M. A1 - Mitchell, A. M. W. A1 - Moderski, R. A1 - Mohamed, M. A1 - Mohrmann, L. A1 - Mora, K. A1 - Moulin, Emmanuel A1 - Murach, T. A1 - Nakashima, S. A1 - de Naurois, M. A1 - Niederwanger, F. A1 - Niemiec, J. A1 - Oakes, L. A1 - Odaka, H. A1 - Ohm, S. A1 - Ostrowski, M. A1 - Oya, I. A1 - Padovani, M. A1 - Panter, M. A1 - Parsons, R. D. A1 - Pekeur, N. W. A1 - Pelletier, G. A1 - Perennes, C. A1 - Petrucci, P. -O. A1 - Peyaud, B. A1 - Piel, Q. A1 - Pita, S. A1 - Poon, H. A1 - Prokhorov, D. A1 - Prokoph, H. A1 - Puehlhofer, G. A1 - Punch, M. A1 - Quirrenbach, A. A1 - Raab, S. A1 - Rauth, R. A1 - Reimer, A. A1 - Reimer, O. A1 - Renaud, M. A1 - de los Reyes, R. A1 - Richter, S. A1 - Rieger, F. A1 - Romoli, C. A1 - Rowell, G. A1 - Rudak, B. A1 - Rulten, C. B. A1 - Sahakian, V. A1 - Saito, S. A1 - Salek, D. A1 - Sanchez, David M. A1 - Santangelo, Andrea A1 - Sasaki, M. A1 - Schlickeiser, R. A1 - Schussler, F. A1 - Schulz, A. A1 - Schwanke, U. A1 - Schwemmer, S. A1 - Seglar-Arroyo, M. A1 - Settimo, M. A1 - Seyffert, A. S. A1 - Shafi, N. A1 - Shilon, I. A1 - Simoni, R. A1 - Sol, H. A1 - Spanier, F. A1 - Spengler, G. A1 - Spies, F. A1 - Stawarz, L. A1 - Steenkamp, R. A1 - Stegmann, Christian A1 - Stycz, K. A1 - Sushch, Iurii A1 - Takahashi, T. A1 - Tavernet, J. -P. A1 - Tavernier, T. A1 - Taylor, A. M. A1 - Terrier, R. A1 - Tibaldo, L. A1 - Tiziani, D. A1 - Tluczykont, M. A1 - Trichard, C. A1 - Tsuji, N. A1 - Tuffs, R. A1 - Uchiyama, Y. A1 - van der Walt, D. J. A1 - van Eldik, C. A1 - van Rensburg, C. A1 - van Soelen, B. A1 - Vasileiadis, G. A1 - Veh, J. A1 - Venter, C. A1 - Viana, A. A1 - Vincent, P. A1 - Vink, J. A1 - Voisin, F. A1 - Voelk, H. J. A1 - Vuillaume, T. A1 - Wadiasingh, Z. A1 - Wagner, S. J. A1 - Wagner, P. A1 - Wagner, R. M. A1 - White, R. A1 - Wierzcholska, A. A1 - Willmann, P. A1 - Woernlein, A. A1 - Wouters, D. A1 - Yang, R. A1 - Zaborov, D. A1 - Zacharias, M. A1 - Zanin, R. A1 - Zdziarski, A. A. A1 - Zech, Alraune A1 - Zefi, F. A1 - Ziegler, A. A1 - Zywucka, N. T1 - Measurement of the EBL spectral energy distribution using the VHE gamma-ray spectra of HESS blazars JF - Astronomy and astrophysics : an international weekly journal N2 - Very high-energy gamma rays (VHE, E greater than or similar to 100 GeV) propagating over cosmological distances can interact with the low-energy photons of the extragalactic background light (EBL) and produce electron-positron pairs. The transparency of the Universe to VHE gamma rays is then directly related to the spectral energy distribution (SED) of the EBL. The observation of features in the VHE energy spectra of extragalactic sources allows the EBL to be measured, which otherwise is very difficult. An EBL model-independent measurement of the EBL SED with the H.E.S.S. array of Cherenkov telescopes is presented. It was obtained by extracting the EBL absorption signal from the reanalysis of high-quality spectra of blazars. From H.E.S.S. data alone the EBL signature is detected at a significance of 9.5 sigma, and the intensity of the EBL obtained in different spectral bands is presented together with the associated gamma-ray horizon. KW - gamma rays: galaxies KW - BL Lacertae objects: general KW - cosmic background radiation KW - infrared: diffuse background Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201731200 SN - 1432-0746 VL - 606 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Abdalla, Hassan E. A1 - Abramowski, Attila A1 - Aharonian, Felix A. A1 - Benkhali, Faical Ait A1 - Anguner, Ekrem Oǧuzhan A1 - Arakawa, M. A1 - Arrieta, M. A1 - Aubert, Pierre A1 - Backes, Michael A1 - Balzer, Arnim A1 - Barnard, Michelle A1 - Becherini, Yvonne A1 - Tjus, J. Becker A1 - Berge, David A1 - Bernhard, Sabrina A1 - Bernlöhr, K. A1 - Blackwell, R. A1 - Böttcher, Markus A1 - Boisson, Catherine A1 - Bolmont, J. A1 - Bonnefoy, S. A1 - Bordas, Pol A1 - Bregeon, Johan A1 - Brun, Francois A1 - Brun, Pierre A1 - Bryan, Mark A1 - Buechele, M. A1 - Bulik, Tomasz A1 - Capasso, M. A1 - Caroff, S. A1 - Carosi, A. A1 - Casanova, Sabrina A1 - Cerruti, M. A1 - Chakraborty, N. A1 - Chaves, Ryan C. G. A1 - Chen, Andrew A1 - Chevalier, J. A1 - Colafrancesco, Sergio A1 - Condon, B. A1 - Conrad, Jan A1 - Davids, I. D. A1 - Decock, J. A1 - Deil, C. A1 - Devin, J. A1 - deWilt, P. A1 - Dirson, L. A1 - Djannati-Atai, A. A1 - Donath, A. A1 - Dutson, K. A1 - Dyks, J. A1 - Edwards, T. A1 - Egberts, Kathrin A1 - Emery, G. A1 - Ernenwein, J. -P. A1 - Eschbach, S. A1 - Farnier, C. A1 - Fegan, S. A1 - Fernandes, M. V. A1 - Fiasson, A. A1 - Fontaine, G. A1 - Funk, S. A1 - Fuessling, M. A1 - Gabici, S. A1 - Gallant, Y. A. A1 - Garrigoux, T. A1 - Gate, F. A1 - Giavitto, G. A1 - Giebels, B. A1 - Glawion, D. A1 - Glicenstein, J. F. A1 - Gottschall, D. A1 - Grondin, M. -H. A1 - Hahn, J. A1 - Haupt, M. A1 - Hawkes, J. A1 - Heinzelmann, G. A1 - Henri, G. A1 - Hermann, G. A1 - Hinton, James Anthony A1 - Hofmann, W. A1 - Hoischen, Clemens A1 - Holch, Tim Lukas A1 - Holler, M. A1 - Horns, D. A1 - Ivascenko, A. A1 - Iwasaki, H. A1 - Jacholkowska, A. A1 - Jamrozy, M. A1 - Jankowsky, D. A1 - Jankowsky, F. A1 - Jingo, M. A1 - Jouvin, L. A1 - Jung-Richardt, I. A1 - Kastendieck, M. A. A1 - Katarzynski, K. A1 - Katsuragawa, M. A1 - Katz, U. A1 - Kerszberg, D. A1 - Khangulyan, D. A1 - Khelifi, B. A1 - King, J. A1 - Klepser, S. A1 - Klochkov, D. A1 - Kluzniak, W. A1 - Komin, Nu. A1 - Kosack, K. A1 - Krakau, S. A1 - Kraus, M. A1 - Kruer, P. P. A1 - Laffon, H. A1 - Lamanna, G. A1 - Lau, J. A1 - Lees, J. -P. A1 - Lefaucheur, J. A1 - Lemiere, A. A1 - Lemoine-Goumard, M. A1 - Lenain, J. -P. A1 - Leser, Eva A1 - Lohse, T. A1 - Lorentz, M. A1 - Liu, R. A1 - Lopez-Coto, R. A1 - Lypova, I. A1 - Malyshev, D. A1 - Marandon, V. A1 - Marcowith, Alexandre A1 - Mariaud, C. A1 - Marx, R. A1 - Maurin, G. A1 - Maxted, N. A1 - Mayer, M. A1 - Meintjes, P. J. A1 - Meyer, M. A1 - Mitchell, A. M. W. A1 - Moderski, R. A1 - Mohamed, M. A1 - Mohrmann, L. A1 - Mora, K. A1 - Moulin, Emmanuel A1 - Murach, T. A1 - Nakashima, S. A1 - de Naurois, M. A1 - Ndiyavala, H. A1 - Niederwanger, F. A1 - Niemiec, J. A1 - Oakes, L. A1 - Odaka, H. A1 - Ohm, S. A1 - Ostrowski, M. A1 - Oya, I. A1 - Padovani, M. A1 - Panter, M. A1 - Parsons, R. D. A1 - Pekeur, N. W. A1 - Pelletier, G. A1 - Perennes, C. A1 - Petrucci, P. -O. A1 - Peyaud, B. A1 - Piel, Q. A1 - Pita, S. A1 - Poireau, V. A1 - Poon, H. A1 - Prokhorov, D. A1 - Prokoph, H. A1 - Puehlhofer, G. A1 - Punch, M. A1 - Quirrenbach, A. A1 - Raab, S. A1 - Rauth, R. A1 - Reimer, A. A1 - Reimer, O. A1 - Renaud, M. A1 - de los Reyes, R. A1 - Rieger, F. A1 - Rinchiuso, L. A1 - Romoli, C. A1 - Rowell, G. A1 - Rudak, B. A1 - Rulten, C. B. A1 - Sahakian, V. A1 - Saito, S. A1 - Sanchez, David M. A1 - Santangelo, Andrea A1 - Sasaki, M. A1 - Schlickeiser, R. A1 - Schussler, F. A1 - Schulz, A. A1 - Schwanke, U. A1 - Schwemmer, S. A1 - Seglar-Arroyo, M. A1 - Settimo, M. A1 - Seyffert, A. S. A1 - Shafi, N. A1 - Shilon, I. A1 - Shiningayamwe, K. A1 - Simoni, R. A1 - Sol, H. A1 - Spanier, F. A1 - Spir-Jacob, M. A1 - Stawarz, L. A1 - Steenkamp, R. A1 - Stegmann, Christian A1 - Steppa, Constantin Beverly A1 - Sushch, Iurii A1 - Takahashi, T. A1 - Tavernet, J. -P. A1 - Tavernier, T. A1 - Taylor, A. M. A1 - Terrier, R. A1 - Tibaldo, L. A1 - Tiziani, D. A1 - Tluczykont, M. A1 - Trichard, C. A1 - Tsirou, M. A1 - Tsuji, N. A1 - Tuffs, R. A1 - Uchiyama, Y. A1 - van der Walt, D. J. A1 - van Eldik, C. A1 - van Rensburg, C. A1 - van Soelen, B. A1 - Vasileiadis, G. A1 - Veh, J. A1 - Venter, C. A1 - Viana, A. A1 - Vincent, P. A1 - Vink, J. A1 - Voisin, F. A1 - Voelk, H. J. A1 - Vuillaume, T. A1 - Wadiasingh, Z. A1 - Wagner, S. J. A1 - Wagner, P. A1 - Wagner, R. M. A1 - White, R. A1 - Wierzcholska, A. A1 - Willmann, P. A1 - Woernlein, A. A1 - Wouters, D. A1 - Yang, R. A1 - Zaborov, D. A1 - Zacharias, M. A1 - Zanin, R. A1 - Zdziarski, A. A. A1 - Zech, Alraune A1 - Zefi, F. A1 - Ziegler, A. A1 - Zorn, J. A1 - Zywucka, N. T1 - TeV Gamma-Ray Observations of the Binary Neutron Star Merger GW170817 with HESS JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters N2 - We search for high-energy gamma-ray emission from the binary neutron star merger GW170817 with the H.E.S.S. Imaging Air Cherenkov Telescopes. The observations presented here have been obtained starting only 5.3 hr after GW170817. The H.E.S.S. target selection identified regions of high probability to find a counterpart of the gravitational-wave event. The first of these regions contained the counterpart SSS17a that has been identified in the optical range several hours after our observations. We can therefore present the first data obtained by a ground-based pointing instrument on this object. A subsequent monitoring campaign with the H.E.S.S. telescopes extended over several days, covering timescales from 0.22 to 5.2 days and energy ranges between 270 GeV to 8.55 TeV. No significant gamma-ray emission has been found. The derived upper limits on the very-high-energy gamma-ray flux for the first time constrain non-thermal, high-energy emission following the merger of a confirmed binary neutron star system. KW - gamma-ray burst: individual (GRB 170817A) KW - gamma rays: general KW - gravitational waves Y1 - 2017 U6 - https://doi.org/10.3847/2041-8213/aa97d2 SN - 2041-8205 SN - 2041-8213 VL - 850 SP - 628 EP - 650 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Koc, Azize A1 - Reinhardt, M. A1 - Reppert, Alexander von A1 - Roessle, Matthias A1 - Leitenberger, Wolfram A1 - Dumesnil, K. A1 - Gaal, Peter A1 - Zamponi, Flavio A1 - Bargheer, Matias T1 - Ultrafast x-ray diffraction thermometry measures the influence of spin excitations on the heat transport through nanolayers JF - Physical review : B, Condensed matter and materials physics N2 - We investigate the heat transport through a rare earth multilayer system composed of yttrium (Y), dysprosium (Dy), and niobium (Nb) by ultrafast x-ray diffraction. This is an example of a complex heat flow problem on the nanoscale, where several different quasiparticles carry the heat and conserve a nonequilibrium for more than 10 ns. The Bragg peak positions of each layer represent layer-specific thermometers that measure the energy flow through the sample after excitation of the Y top layer with fs-laser pulses. In an experiment-based analytic solution to the nonequilibrium heat transport problem, we derive the individual contributions of the spins and the coupled electron-lattice system to the heat conduction. The full characterization of the spatiotemporal energy flow at different starting temperatures reveals that the spin excitations of antiferromagnetic Dy speed up the heat transport into the Dy layer at low temperatures, whereas the heat transport through this layer and further into the Y and Nb layers underneath is slowed down. The experimental findings are compared to the solution of the heat equation using macroscopic temperature-dependent material parameters without separation of spin and phonon contributions to the heat. We explain why the simulated energy density matches our experiment-based derivation of the heat transport, although the simulated thermoelastic strain in this simulation is not even in qualitative agreement. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevB.96.014306 SN - 2469-9950 SN - 2469-9969 VL - 96 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Abdalla, H. A1 - Abramowski, A. A1 - Aharonian, Felix A. A1 - Benkhali, F. Ait A1 - Akhperjanian, A. G. A1 - Andersson, T. A1 - Anguener, E. O. A1 - Arrieta, M. A1 - Aubert, P. A1 - Backes, M. A1 - Balzer, A. A1 - Barnard, M. A1 - Becherini, Y. A1 - Tjus, J. Becker A1 - Berge, D. A1 - Bernhard, S. A1 - Bernlorhr, K. A1 - Blackwell, R. A1 - Bottcher, M. A1 - Boisson, C. A1 - Bolmont, J. A1 - Bordas, Pol A1 - Bregeon, J. A1 - Brun, F. A1 - Brun, P. A1 - Bryan, M. A1 - Bulik, T. A1 - Capasso, M. A1 - Carr, J. A1 - Casanova, Sabrina A1 - Cerruti, M. A1 - Chakraborty, N. A1 - Chalme-Calvet, R. A1 - Chaves, R. C. G. A1 - Chen, A. A1 - Chevalier, J. A1 - Chretien, M. A1 - Colafrancesco, S. A1 - Cologna, G. A1 - Condon, B. A1 - Conrad, J. A1 - Cui, Y. A1 - Davids, I. D. A1 - Decock, J. A1 - Degrange, B. A1 - Deil, C. A1 - Devin, J. A1 - deWilt, P. A1 - Dirson, L. A1 - Djannati-Atai, A. A1 - Domainko, W. A1 - Donath, A. A1 - Dubus, G. A1 - Dutson, K. A1 - Dyks, J. A1 - Edwards, T. A1 - Egberts, Kathrin A1 - Eger, P. A1 - Ernenwein, J. -P. A1 - Eschbach, S. A1 - Farnier, C. A1 - Fegan, S. A1 - Fernandes, M. V. A1 - Fiasson, A. A1 - Fontaine, G. A1 - Foerster, A. A1 - Funk, S. A1 - Fuessling, M. A1 - Gabici, S. A1 - Gajdus, M. A1 - Gallant, Y. A. A1 - Garrigoux, T. A1 - Giavitto, G. A1 - Giebels, B. A1 - Glicenstein, J. F. A1 - Gottschall, D. A1 - Goyal, A. A1 - Grondin, M. -H. A1 - Hadasch, D. A1 - Hahn, J. A1 - Haupt, M. A1 - Hawkes, J. A1 - Heinzelmann, G. A1 - Henri, G. A1 - Hermann, G. A1 - Hervet, O. A1 - Hinton, J. A. A1 - Hofmann, W. A1 - Hoischen, Clemens A1 - Holler, M. A1 - Horns, D. A1 - Ivascenko, A. A1 - Jacholkowska, A. A1 - Jamrozy, M. A1 - Janiak, M. A1 - Jankowsky, D. A1 - Jankowsky, F. A1 - Jingo, M. A1 - Jogler, T. A1 - Jouvin, L. A1 - Jung-Richardt, I. A1 - Kastendieck, M. A. A1 - Katarzynski, K. A1 - Katz, U. A1 - Kerszberg, D. A1 - Khelifi, B. A1 - Er, M. Kie Ff A1 - King, J. A1 - Klepser, S. A1 - Klochkov, D. A1 - Kluzniak, W. A1 - Kolitzus, D. A1 - Komin, Nu. A1 - Kosack, K. A1 - Krakau, S. A1 - Kraus, M. A1 - Krayzel, F. A1 - Kruger, P. P. A1 - Laffon, H. A1 - Lamanna, G. A1 - Lau, J. A1 - Lees, J. -P. A1 - Lefaucheur, J. A1 - Lefranc, V. A1 - Lemiere, A. A1 - Lemoine-Goumard, M. A1 - Lenain, J. -P. A1 - Leser, E. A1 - Lohse, T. A1 - Lorentz, M. A1 - Liu, R. A1 - Lopez-Coto, R. A1 - Lypova, I. A1 - Marandon, V. A1 - Marcowith, Alexandre A1 - Mariaud, C. A1 - Marx, R. A1 - Maurin, G. A1 - Maxted, N. A1 - Mayer, M. A1 - Meintjes, P. J. A1 - Meyer, M. A1 - Mitchell, A. M. W. A1 - Moderski, R. A1 - Mohamed, M. A1 - Mohrmann, L. A1 - Mora, K. A1 - Moulin, Emmanuel A1 - Murach, T. A1 - de Naurois, M. A1 - Niederwanger, F. A1 - Niemiec, J. A1 - Oakes, L. A1 - Odaka, H. A1 - Oettl, S. A1 - Ohm, S. A1 - Ostrowski, M. A1 - Oya, I. A1 - Padovani, M. A1 - Panter, M. A1 - Parsons, R. D. A1 - Pekeur, N. W. A1 - Pelletier, G. A1 - Perennes, C. A1 - Petrucci, P. -O. A1 - Peyaud, B. A1 - Piel, Q. A1 - Pita, S. A1 - Poon, H. A1 - Prokhorov, D. A1 - Prokoph, H. A1 - Puehlhofer, G. A1 - Punch, M. A1 - Quirrenbach, A. A1 - Raab, S. A1 - Reimer, A. A1 - Reimer, O. A1 - Renaud, M. A1 - de los Reyes, R. A1 - Rieger, F. A1 - Romoli, C. A1 - Rosier-Lees, S. A1 - Rowell, G. A1 - Rudak, B. A1 - Rulten, C. B. A1 - Sahakian, V. A1 - Salek, D. A1 - Sanchez, D. A. A1 - Santangelo, Andrea A1 - Sasaki, M. A1 - Schlickeiser, R. A1 - Schussler, F. A1 - Schulz, A. A1 - Schwanke, U. A1 - Schwemmer, S. A1 - Settimo, M. A1 - Seyffert, A. S. A1 - Shafi, N. A1 - Shilon, I. A1 - Simoni, R. A1 - Sol, H. A1 - Spanier, F. A1 - Spengler, G. A1 - Spies, F. A1 - Ert, Ff A1 - Stawarz, L. A1 - Steenkamp, R. A1 - Stegmann, Christian Michael A1 - Stinzing, F. A1 - Stycz, K. A1 - Sushch, I. A1 - Tavernet, J. -P. A1 - Tavernier, T. A1 - Taylor, A. M. A1 - Terrier, R. A1 - Tibaldo, L. A1 - Tiziani, D. A1 - Tluczykont, M. A1 - Trichard, C. A1 - Tuffs, R. A1 - Uchiyama, Y. A1 - van der Walt, D. J. A1 - van Eldik, C. A1 - van Rensburg, C. A1 - van Soelen, B. A1 - Vasileiadis, G. A1 - Veh, J. A1 - Venter, C. A1 - Viana, A. A1 - Vincent, P. A1 - Vink, J. A1 - Voisin, F. A1 - Voelk, H. J. A1 - Vuillaume, T. A1 - Wadiasingh, Z. A1 - Wagner, S. J. A1 - Wagner, P. A1 - Wagner, R. M. A1 - White, R. A1 - Wierzcholska, A. A1 - Willmann, P. A1 - Woernlein, A. A1 - Wouters, D. A1 - Yang, R. A1 - Zabalza, V. A1 - Zaborov, D. A1 - Zacharias, M. A1 - Zdziarski, A. A. A1 - Zech, Alraune A1 - Zefi, F. A1 - Ziegler, A. A1 - Zywucka, N. T1 - Characterizing the gamma-ray long-term variability of PKS2155 304 with HESS and Fermi-LAT JF - Astronomy and astrophysics : an international weekly journal N2 - Studying the temporal variability of BL Lac objects at the highest energies provides unique insights into the extreme physical processes occurring in relativistic jets and in the vicinity of super-massive black holes. To this end, the long-term variability of the BL Lac object PKS 2155 304 is analyzed in the high (HE, 100MeV < E < 300 GeV) and very high energy (VHE, E > 200 GeV) gamma-ray domain. Over the course of similar to 9 yr of H. E. S. S. observations the VHE light curve in the quiescent state is consistent with a log-normal behavior. The VHE variability in this state is well described by flicker noise (power-spectral-density index beta(VHE) = 1 .10(+ 0 : 10) (0 : 13)) on timescales larger than one day. An analysis of similar to 5.5 yr of HE Fermi-LAT data gives consistent results (beta(HE) = 1 : 20(+ 0 : 21) (0 : 23), on timescales larger than 10 days) compatible with the VHE findings. The HE and VHE power spectral densities show a scale invariance across the probed time ranges. A direct linear correlation between the VHE and HE fluxes could neither be excluded nor firmly established. These long-term-variability properties are discussed and compared to the red noise behavior (beta similar to 2) seen on shorter timescales during VHE-flaring states. The difference in power spectral noise behavior at VHE energies during quiescent and flaring states provides evidence that these states are influenced by different physical processes, while the compatibility of the HE and VHE long-term results is suggestive of a common physical link as it might be introduced by an underlying jet-disk connection. KW - galaxies: active KW - BL Lacertae objects: individual: PKS 2155-304 KW - gamma rays: galaxies KW - galaxies: jets KW - galaxies: nuclei KW - radiation mechanisms: non-thermal Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201629419 SN - 1432-0746 SN - 0004-6361 VL - 598 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Koc, A. A1 - Reinhardt, M. A1 - Reppert, Alexander von A1 - Rössle, Matthias A1 - Leitenberger, Wolfram A1 - Gleich, M. A1 - Weinelt, M. A1 - Zamponi, Flavio A1 - Bargheer, Matias T1 - Grueneisen-approach for the experimental determination of transient spin and phonon energies from ultrafast x-ray diffraction data: gadolinium JF - Journal of physics : Condensed matter N2 - We study gadolinium thin films as a model system for ferromagnets with negative thermal expansion. Ultrashort laser pulses heat up the electronic subsystem and we follow the transient strain via ultrafast x-ray diffraction. In terms of a simple Grueneisen approach, the strain is decomposed into two contributions proportional to the thermal energy of spin and phonon subsystems. Our analysis reveals that upon femtosecond laser excitation, phonons and spins can be driven out of thermal equilibrium for several nanoseconds. KW - ultrafast KW - x-ray diffraction KW - magnetostriction KW - nonequilibrium KW - spin KW - phonon KW - rare earth Y1 - 2017 U6 - https://doi.org/10.1088/1361-648X/aa7187 SN - 0953-8984 SN - 1361-648X VL - 29 SP - 5884 EP - 5891 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Davidsen, Joern A1 - Kwiatek, Grzegorz A1 - Charalampidou, Elli-Maria A1 - Goebel, Thomas H. W. A1 - Stanchits, Sergei A1 - Rueck, Marc A1 - Dresen, Georg T1 - Triggering Processes in Rock Fracture JF - Physical review letters N2 - We study triggering processes in triaxial compression experiments under a constant displacement rate on sandstone and granite samples using spatially located acoustic emission events and their focal mechanisms. We present strong evidence that event-event triggering plays an important role in the presence of large-scale or macrocopic imperfections, while such triggering is basically absent if no significant imperfections are present. In the former case, we recover all established empirical relations of aftershock seismicity including the Gutenberg-Richter relation, a modified version of the Omori-Utsu relation and the productivity relation-despite the fact that the activity is dominated by compaction-type events and triggering cascades have a swarmlike topology. For the Gutenberg-Richter relations, we find that the b value is smaller for triggered events compared to background events. Moreover, we show that triggered acoustic emission events have a focal mechanism much more similar to their associated trigger than expected by chance. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevLett.119.068501 SN - 0031-9007 SN - 1079-7114 VL - 119 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Reese, Ronja A1 - Gudmundsson, Gudmundur Hilmar A1 - Levermann, Anders A1 - Winkelmann, Ricarda T1 - The far reach of ice-shelf thinning in Antarctica JF - Nature climate change N2 - Floating ice shelves, which fringe most of Antarctica’s coastline, regulate ice flow into the Southern Ocean1,2,3. Their thinning4,5,6,7 or disintegration8,9 can cause upstream acceleration of grounded ice and raise global sea levels. So far the effect has not been quantified in a comprehensive and spatially explicit manner. Here, using a finite-element model, we diagnose the immediate, continent-wide flux response to different spatial patterns of ice-shelf mass loss. We show that highly localized ice-shelf thinning can reach across the entire shelf and accelerate ice flow in regions far from the initial perturbation. As an example, this ‘tele-buttressing’ enhances outflow from Bindschadler Ice Stream in response to thinning near Ross Island more than 900 km away. We further find that the integrated flux response across all grounding lines is highly dependent on the location of imposed changes: the strongest response is caused not only near ice streams and ice rises, but also by thinning, for instance, well-within the Filchner–Ronne and Ross Ice Shelves. The most critical regions in all major ice shelves are often located in regions easily accessible to the intrusion of warm ocean waters10,11,12, stressing Antarctica’s vulnerability to changes in its surrounding ocean. Y1 - 2017 U6 - https://doi.org/10.1038/s41558-017-0020-x SN - 1758-678X SN - 1758-6798 VL - 8 IS - 1 SP - 53 EP - 57 PB - Nature Publ. Group CY - London ER -