TY - JOUR A1 - Mayer, Dennis A1 - Lever, Fabiano A1 - Picconi, David A1 - Metje, Jan A1 - Ališauskas, Skirmantas A1 - Calegari, Francesca A1 - Düsterer, Stefan A1 - Ehlert, Christopher A1 - Feifel, Raimund A1 - Niebuhr, Mario A1 - Manschwetus, Bastian A1 - Kuhlmann, Marion A1 - Mazza, Tommaso A1 - Robinson, Matthew Scott A1 - Squibb, Richard James A1 - Trabattoni, Andrea A1 - Wallner, Måns A1 - Saalfrank, Peter A1 - Wolf, Thomas J. A. A1 - Gühr, Markus T1 - Following excited-state chemical shifts in molecular ultrafast x-ray photoelectron spectroscopy JF - Nature Communications N2 - The conversion of photon energy into other energetic forms in molecules is accompanied by charge moving on ultrafast timescales. We directly observe the charge motion at a specific site in an electronically excited molecule using time-resolved x-ray photoelectron spectroscopy (TR-XPS). We extend the concept of static chemical shift from conventional XPS by the excited-state chemical shift (ESCS), which is connected to the charge in the framework of a potential model. This allows us to invert TR-XPS spectra to the dynamic charge at a specific atom. We demonstrate the power of TR-XPS by using sulphur 2p-core-electron-emission probing to study the UV-excited dynamics of 2-thiouracil. The method allows us to discover that a major part of the population relaxes to the molecular ground state within 220–250 fs. In addition, a 250-fs oscillation, visible in the kinetic energy of the TR-XPS, reveals a coherent exchange of population among electronic states. Y1 - 2022 U6 - https://doi.org/10.1038/s41467-021-27908-y SN - 2041-1723 VL - 13 PB - Springer Nature CY - Berlin ER - TY - JOUR A1 - Petrov, Polina A1 - Singer, Leo P. A1 - Coughlin, Michael W. A1 - Kumar, Vishwesh A1 - Almualla, Mouza A1 - Anand, Shreya A1 - Bulla, Mattia A1 - Dietrich, Tim A1 - Foucart, Francois A1 - Guessoum, Nidhal T1 - Data-driven expectations for electromagnetic counterpart searches based on LIGO/Virgo public alerts JF - The astrophysical journal : an international review of spectroscopy and astronomical physics; part 1 N2 - Searches for electromagnetic counterparts of gravitational-wave signals have redoubled since the first detection in 2017 of a binary neutron star merger with a gamma-ray burst, optical/infrared kilonova, and panchromatic afterglow. Yet, one LIGO/Virgo observing run later, there has not yet been a second, secure identification of an electromagnetic counterpart. This is not surprising given that the localization uncertainties of events in LIGO and Virgo's third observing run, O3, were much larger than predicted. We explain this by showing that improvements in data analysis that now allow LIGO/Virgo to detect weaker and hence more poorly localized events have increased the overall number of detections, of which well-localized, gold-plated events make up a smaller proportion overall. We present simulations of the next two LIGO/Virgo/KAGRA observing runs, O4 and O5, that are grounded in the statistics of O3 public alerts. To illustrate the significant impact that the updated predictions can have, we study the follow-up strategy for the Zwicky Transient Facility. Realistic and timely forecasting of gravitational-wave localization accuracy is paramount given the large commitments of telescope time and the need to prioritize which events are followed up. We include a data release of our simulated localizations as a public proposal planning resource for astronomers. Y1 - 2022 U6 - https://doi.org/10.3847/1538-4357/ac366d SN - 1538-4357 VL - 924 IS - 2 PB - Institute of Physics Publ. CY - London ER - TY - JOUR A1 - Perdigón-Toro, Lorena A1 - Le Quang Phuong, A1 - Eller, Fabian A1 - Freychet, Guillaume A1 - Saglamkaya, Elifnaz A1 - Khan, Jafar A1 - Wei, Qingya A1 - Zeiske, Stefan A1 - Kroh, Daniel A1 - Wedler, Stefan A1 - Koehler, Anna A1 - Armin, Ardalan A1 - Laquai, Frederic A1 - Herzig, Eva M. A1 - Zou, Yingping A1 - Shoaee, Safa A1 - Neher, Dieter T1 - Understanding the role of order in Y-series non-fullerene solar cells to realize high open-circuit voltages JF - Advanced energy materials N2 - Non-fullerene acceptors (NFAs) as used in state-of-the-art organic solar cells feature highly crystalline layers that go along with low energetic disorder. Here, the crucial role of energetic disorder in blends of the donor polymer PM6 with two Y-series NFAs, Y6, and N4 is studied. By performing temperature-dependent charge transport and recombination studies, a consistent picture of the shape of the density of state distributions for free charges in the two blends is developed, allowing an analytical description of the dependence of the open-circuit voltage V-OC on temperature and illumination intensity. Disorder is found to influence the value of the V-OC at room temperature, but also its progression with temperature. Here, the PM6:Y6 blend benefits substantially from its narrower state distributions. The analysis also shows that the energy of the equilibrated free charge population is well below the energy of the NFA singlet excitons for both blends and possibly below the energy of the populated charge transfer manifold, indicating a down-hill driving force for free charge formation. It is concluded that energetic disorder of charge-separated states has to be considered in the analysis of the photovoltaic properties, even for the more ordered PM6:Y6 blend. KW - energetic disorder KW - non-fullerene acceptors KW - open-circuit voltage KW - organic solar cells Y1 - 2022 U6 - https://doi.org/10.1002/aenm.202103422 SN - 1614-6832 SN - 1614-6840 VL - 12 IS - 12 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Doerries, Timo J. A1 - Chechkin, Aleksei A1 - Schumer, Rina A1 - Metzler, Ralf T1 - Rate equations, spatial moments, and concentration profiles for mobile-immobile models with power-law and mixed waiting time distributions JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We present a framework for systems in which diffusion-advection transport of a tracer substance in a mobile zone is interrupted by trapping in an immobile zone. Our model unifies different model approaches based on distributed-order diffusion equations, exciton diffusion rate models, and random-walk models for multirate mobile-immobile mass transport. We study various forms for the trapping time dynamics and their effects on the tracer mass in the mobile zone. Moreover, we find the associated breakthrough curves, the tracer density at a fixed point in space as a function of time, and the mobile and immobile concentration profiles and the respective moments of the transport. Specifically, we derive explicit forms for the anomalous transport dynamics and an asymptotic power-law decay of the mobile mass for a Mittag-Leffler trapping time distribution. In our analysis we point out that even for exponential trapping time densities, transient anomalous transport is observed. Our results have direct applications in geophysical contexts, but also in biological, soft matter, and solid state systems. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevE.105.014105 SN - 2470-0045 SN - 2470-0053 VL - 105 IS - 1 PB - The American Institute of Physics CY - Woodbury, NY ER - TY - JOUR A1 - Kupfer, Thomas A1 - Bauer, Evan B. A1 - van Roestel, Jan A1 - Bellm, Eric C. A1 - Bildsten, Lars A1 - Fuller, Jim A1 - Prince, Thomas A. A1 - Heber, Ulrich A1 - Geier, Stephan A1 - Green, Matthew J. A1 - Kulkarni, Shrinivas R. A1 - Bloemen, Steven A1 - Laher, Russ R. A1 - Rusholme, Ben A1 - Schneider, David T1 - Discovery of a Double-detonation Thermonuclear Supernova Progenitor JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters N2 - We present the discovery of a new double-detonation progenitor system consisting of a hot subdwarf B (sdB) binary with a white dwarf companion with a P (orb) = 76.34179(2) minutes orbital period. Spectroscopic observations are consistent with an sdB star during helium core burning residing on the extreme horizontal branch. Chimera light curves are dominated by ellipsoidal deformation of the sdB star and a weak eclipse of the companion white dwarf. Combining spectroscopic and light curve fits, we find a low-mass sdB star, M (sdB) = 0.383 +/- 0.028 M (circle dot) with a massive white dwarf companion, M (WD) = 0.725 +/- 0.026 M (circle dot). From the eclipses we find a blackbody temperature for the white dwarf of 26,800 K resulting in a cooling age of approximate to 25 Myr whereas our MESA model predicts an sdB age of approximate to 170 Myr. We conclude that the sdB formed first through stable mass transfer followed by a common envelope which led to the formation of the white dwarf companion approximate to 25 Myr ago. Using the MESA stellar evolutionary code we find that the sdB star will start mass transfer in approximate to 6 Myr and in approximate to 60 Myr the white dwarf will reach a total mass of 0.92 M (circle dot) with a thick helium layer of 0.17 M (circle dot). This will lead to a detonation that will likely destroy the white dwarf in a peculiar thermonuclear supernova. PTF1 J2238+7430 is only the second confirmed candidate for a double-detonation thermonuclear supernova. Using both systems we estimate that at least approximate to 1% of white dwarf thermonuclear supernovae originate from sdB+WD binaries with thick helium layers, consistent with the small number of observed peculiar thermonuclear explosions. Y1 - 2022 U6 - https://doi.org/10.3847/2041-8213/ac48f1 SN - 2041-8205 SN - 2041-8213 VL - 925 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Shayduk, Roman A1 - Hallmann, Jörg A1 - Rodriguez-Fernandez, Angel A1 - Scholz, Markus A1 - Lu, Wei A1 - Bösenberg, Ulrike A1 - Möller, Johannes A1 - Zozulya, Alexey A1 - Jiang, Man A1 - Wegner, Ulrike A1 - Secareanu, Radu-Costin A1 - Palmer, Guido A1 - Emons, Moritz A1 - Lederer, Max A1 - Volkov, Sergey A1 - Lindfors-Vrejoiu, Ionela A1 - Schick, Daniel A1 - Herzog, Marc A1 - Bargheer, Matias A1 - Madsen, Anders T1 - Femtosecond x-ray diffraction study of multi-THz coherent phonons in SrTiO3 JF - Applied physics letters N2 - We report generation of ultra-broadband longitudinal acoustic coherent phonon wavepackets in SrTiO3 (STO) with frequency components extending throughout the first Brillouin zone. The wavepackets are efficiently generated in STO using femtosecond infrared laser excitation of an atomically flat 1.6 nm-thick epitaxial SrRuO3 film. We use femtosecond x-ray diffraction at the European X-Ray Free Electron Laser Facility to study the dispersion and damping of phonon wavepackets. The experimentally determined damping constants for multi-THz frequency phonons compare favorably to the extrapolation of a simple ultrasound damping model over several orders of magnitude. Y1 - 2022 U6 - https://doi.org/10.1063/5.0083256 SN - 0003-6951 SN - 1077-3118 VL - 120 IS - 20 PB - AIP Publishing CY - Melville ER - TY - JOUR A1 - Deb, Marwan A1 - Popova, Elena A1 - Jaffrès, Henri-Yves A1 - Keller, Niels A1 - Bargheer, Matias T1 - Polarization-dependent subpicosecond demagnetization in iron garnets JF - Physical review : B, covering condensed matter and materials physics N2 - Controlling the magnetization dynamics at the fastest speed is a major issue of fundamental condensed matter physics and its applications for data storage and processing technologies. It requires a deep understanding of the interactions between the degrees of freedom in solids, such as spin, electron, and lattice as well as their responses to external stimuli. In this paper, we systematically investigate the fluence dependence of ultrafast magnetization dynamics induced by below-bandgap ultrashort laser pulses in the ferrimagnetic insulators BixY3-xFe5O12 with 1 xBi 3. We demonstrate subpicosecond demagnetization dynamics in this material followed by a very slow remagnetization process. We prove that this demagnetization results from an ultrafast heating of iron garnets by two-photon absorption (TPA), suggesting a phonon-magnon thermalization time of 0.6 ps. We explain the slow remagnetization timescale by the low phonon heat conductivity in garnets. Additionally, we show that the amplitudes of the demagnetization, optical change, and lattice strain can be manipulated by changing the ellipticity of the pump pulses. We explain this phenomenon considering the TPA circular dichroism. These findings open exciting prospects for ultrafast manipulation of spin, charge, and lattice dynamics in magnetic insulators by ultrafast nonlinear optics. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevB.106.184416 SN - 2469-9950 SN - 2469-9969 VL - 106 IS - 18 PB - American Institute of Physics, American Physical Society CY - Woodbury, NY ER - TY - JOUR A1 - Deb, Marwan A1 - Popova, Elena A1 - Jaffrès, Henri-Yves A1 - Keller, Niels A1 - Bargheer, Matias T1 - Controlling high-frequency spin-wave dynamics using double-pulse laser excitation JF - Physical review applied N2 - Manipulating spin waves is highly required for the development of innovative data transport and processing technologies. Recently, the possibility of triggering high-frequency standing spin waves in magnetic insulators using femtosecond laser pulses was discovered, raising the question about how one can manipulate their dynamics. Here we explore this question by investigating the ultrafast magnetiza-tion and spin-wave dynamics induced by double-pulse laser excitation. We demonstrate a suppression or enhancement of the amplitudes of the standing spin waves by precisely tuning the time delay between the two pulses. The results can be understood as the constructive or destructive interference of the spin waves induced by the first and second laser pulses. Our findings open exciting perspectives towards generating single-mode standing spin waves that combine high frequency with large amplitude and low magnetic damping. Y1 - 2022 U6 - https://doi.org/10.1103/PhysRevApplied.18.044001 SN - 2331-7019 VL - 18 IS - 4 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Grassl, Sandra A1 - Ritter, Christoph A1 - Schulz, Alexander T1 - The nature of the Ny-Alesund wind field analysed by high-resolution windlidar data JF - Remote sensing N2 - In this work we present windlidar data for the research village Ny-Alesund located on Svalbard in the European Arctic (78.923 degrees N, 11.928 degrees F) from 2013 to 2021. The data have a resolution of 50 m and 10 min with an overlapping height of about 150 m. The maximum range depends on the meteorologic situation. Up to 1000 m altitude the data availability is better than 71%. We found that the highest wind speeds occur in November and December, the lowest ones in June and July, up to 500 m altitude the wind is channelled strongly in ESE to NW direction parallel to the fjord axis and the synoptic conditions above 1000 m altitude already dominate. While the fraction of windy days (v > 10 m/s) varies significantly from month to month, there is no overall trend of the wind visible in our data set. We define gusts and jets by the requirement of wind maxima v > 2 m/s above and below a wind maximum. In total, more than 24,000 of these events were identified (corresponding to 6% of the time), of which 223 lasted for at least 100 min ("Long Jets"). All of these events are fairly equally distributed over the months relatively to the available data. Further, gusts and jets follow different distributions (in terms of altitude or depths) and occur more frequently for synoptic flow from roughly a southerly direction. Jets do not show a clear correlation between occurrence and synoptic flow. Gusts and jets are not related to cloud cover. We conclude that the atmosphere from 400 m to 1000 m above Ny-Alesund is dominated by a turbulent wind shear zone, which connects the micrometeorology in the atmospheric boundary layer (ABL) with the synoptic flow. KW - windlidar KW - wind field KW - wind channelling KW - jets KW - Ny-Alesund KW - Svalbard KW - Kongsfjord KW - wind speed KW - wind direction KW - turbulent wind shear zone Y1 - 2022 U6 - https://doi.org/10.3390/rs14153771 SN - 2072-4292 VL - 14 IS - 15 PB - MDPI CY - Basel ER - TY - JOUR A1 - Karwinkel, Thiemo A1 - Winklhofer, Michael A1 - Janner, Lars Erik A1 - Brust, Vera A1 - Hüppop, Ommo A1 - Bairlein, Franz A1 - Schmaljohann, Heiko T1 - A magnetic pulse does not affect free-flight navigation behaviour of a medium-distance songbird migrant in spring JF - The journal of experimental biology N2 - Current evidence suggests that migratory animals extract map information from the geomagnetic field for true navigation. The sensory basis underlying this feat is elusive, but presumably involves magnetic particles. A common experimental manipulation procedure consists of pre-treating animals with a magnetic pulse, with the aim of re-magnetising particles to alter the internal representation of the external field prior to a navigation task. Although pulsing provoked deflected bearings in caged songbirds, analogous studies with free-flying songbirds yielded inconsistent results. Here, we pulsed European robins (Erithacus rubecula) at an offshore stopover site during spring migration and monitored their free-flight behaviour with a regional-scale network of radio-receiving stations. We found no pulse effect on departure probability, nocturnal departure timing departure direction or consistency of flight direction. This suggests either no use of the geomagnetic map by our birds, or that magnetic pulses do not affect the sensory system underlying geomagnetic map detection. KW - bird migration KW - magnetic map KW - magnetic-particlebased sensor KW - magnetic pulse KW - magnetoreception KW - navigation Y1 - 2022 U6 - https://doi.org/10.1242/jeb.244473 SN - 0022-0949 SN - 1477-9145 VL - 225 IS - 19 PB - Company of Biologists CY - Cambridge ER -