A5008398607- Electronic and Structural Properties of Oxides
- Magnetic and transport properties of perovskites and related materials
- High-pressure geophysics and materials
- Laser-Matter Interactions and Applications
- Terahertz technology and applications
- Advanced X-ray Imaging Techniques
- Fish Ecology and Management Studies
- Advanced Condensed Matter Physics
- X-ray Spectroscopy and Fluorescence Analysis
- Multiferroics and related materials
- Organic and Molecular Conductors Research
- Spectroscopy and Quantum Chemical Studies
- Magnetic properties of thin films
- Advanced Chemical Physics Studies
- Advanced Electron Microscopy Techniques and Applications
- Semiconductor Quantum Structures and Devices
- Crystallography and Radiation Phenomena
- Laser-Plasma Interactions and Diagnostics
- Physics of Superconductivity and Magnetism
- Metal-Catalyzed Oxygenation Mechanisms
- Ferroelectric and Piezoelectric Materials
- Diamond and Carbon-based Materials Research
- Spectroscopy and Laser Applications
- Laser-induced spectroscopy and plasma
- Ion-surface interactions and analysis
ETH Zurich
2016-2025
Paul Scherrer Institute
2016-2025
Board of the Swiss Federal Institutes of Technology
2019-2024
University of KwaZulu-Natal
2020-2022
Swiss Light Source
2009-2021
Bayer (United States)
2021
Purdue University West Lafayette
2020
Kyoto University
2018
Japan Synchrotron Radiation Research Institute
2018
SPring-8
2018
X-ray absorption spectroscopy is a powerful probe of molecular structure, but it has previously been too slow to track the earliest dynamics after photoexcitation. We investigated ultrafast formation lowest quintet state aqueous iron(II) tris(bipyridine) upon excitation singlet metal-to-ligand-charge-transfer (1MLCT) by femtosecond optical pump/x-ray techniques based on x-ray near-edge structure (XANES). By recording intensity characteristic XANES feature as function laser time delay, we...
Multiferroics have attracted strong interest for potential applications where electric fields control magnetic order. The ultimate speed of via magnetoelectric coupling, however, remains largely unexplored. Here, we report an experiment in which drove spin dynamics multiferroic TbMnO3 with intense few-cycle terahertz (THz) light pulse tuned to resonance electromagnon, electric-dipole active excitation. We observed the resulting motion using time-resolved resonant soft x-ray diffraction. Our...
Time-resolved x-ray diffraction with picosecond temporal resolution is used to observe scattering from impulsively generated coherent acoustic phonons in laser-excited InSb crystals. The observed frequencies and damping rates are agreement a model based on dynamical theory coupled analytic solutions for the laser-induced strain profile. results consistent 12 ps thermal electron-acoustic phonon coupling time together an instantaneous component deformation-potential interaction. Above critical...
Habitat use by juvenile coho salmon (Oncorhynchus kisutch) during spring, summer, and winter was examined in Oregon coastal streams. Coho fry were most abundant backwater pools spring. During more of all types than they glides or riffles. winter, alcoves beaver ponds. Because the apparent strong preference for alcove pond habitat rarity that streams, we concluded if spawning escapement is adequate, production wild smolts streams on Coast probably limited availability adequate habitat.
Structural changes of the iron(II)-tris-bipyridine ([Fe(II)(bpy)(3)](2+)) complex induced by ultrashort pulse excitation and population its short-lived (< or =0.6 ns) quintet high spin state have been detected picosecond x-ray absorption spectroscopy. The structural relaxation from to low was followed over entire lifetime excited state. A combined analysis x-ray-absorption near-edge structure extended fine spectroscopy features delivers an Fe-N bond elongation 0.2 in compared singlet ground
We report on the temporal and spatial stability of first tunable femtosecond undulator hard-x-ray source for ultrafast diffraction absorption experiments. The 2.5-1 Angstrom output radiation is driven by an initial 50 fs laser pulse employing laser-electron slicing technique. By using x-ray to probe laser-induced coherent optical phonons in bulk bismuth, we estimate duration 140+/-30 FWHM with timing drifts below 30 rms measured over 5 days. Optical control lattice motion demonstrated.
We employ grazing-incidence femtosecond x-ray diffraction to characterize the coherent, laser-induced lattice motion of a bismuth crystal as function depth from surface with temporal resolution 193+/-8 fs. The data show direct consequences on carrier diffusion and electron-hole interaction, allowing us estimate an effective rate D=2.3+/-0.3 cm(2)/s for highly excited carriers interaction time 260+/-20
Squeezed states are quantum of a harmonic oscillator in which the variance two conjugate variables each oscillate out phase. Ultrafast optical excitation crystals can create squeezed phonon states, where atomic displacements oscillates due to sudden change interatomic bonding strength. With femtosecond x-ray diffraction we measure squeezing oscillations bismuth and conclude that they consistent with model electronic softens all modes by constant scaling factor.
We use time-resolved optical reflectivity and x-ray diffraction with femtosecond resolution to study the dynamics of structural order parameter charge density wave phase in ${\mathrm{TiSe}}_{2}$. find that energy required melt nonthermally is substantially lower than for thermal suppression comparable condensation energy. This observation, together fact take place on an extremely fast time scale, supports exciton mechanism
Visualizing ferroelectric domains Multiferroic materials support intertwined ferromagnetic and orders, with the magnetic field capable of controlling electric order vice versa. Matsubara et al. used second harmonic generation microscopy to visualize what happens in multiferroic TbMnO 3 when an externally applied changes direction polarization by 90°. Unexpectedly, domain walls, initially parallel vector, did not change their shape or position. The resulting transition from neutral charged...
Using femtosecond time-resolved x-ray diffraction, we directly monitor the coherent lattice dynamics through an ultrafast charge-density-wave-to-metal transition in prototypical Peierls system ${\mathrm{K}}_{0.3}{\mathrm{MoO}}_{3}$ over a wide range of relevant excitation fluences. While low fluence regime follow structural associated with collective amplitude mode; for fluences above melting threshold electronic density modulation observe transient recovery periodic distortion. We can...
We use time-resolved x-ray diffraction and magnetic optical Kerr effect to study the laser induced antiferromagnetic ferromagnetic phase transition in FeRh. The structural response is given by nucleation of independent domains (\tau_1 ~ 30ps). This significantly faster than (\tau_2 60ps) subsequent domain realignment. X-ray shows that two phases co-exist on short time-scales limited speed sound. A model describing both dynamics presented.
We report on the ultrafast dynamics of magnetic order in a single crystal CuO at temperature 207 K response to strong optical excitation using femtosecond resonant x-ray diffraction. In experiment, laser pulse induces sudden, nonequilibrium increase disorder. After short delay ranging from 400 fs 2 ps, we observe changes relative intensity ordering diffraction peaks that indicate shift collinear commensurate phase spiral incommensurate phase. These results ultimate speed for this...
Phase transitions governed by spontaneous time reversal symmetry breaking (TRSB) have long been sought in many quantum systems, including materials with anomalous Hall effect (AHE), cuprate high temperature superconductors, Iridates and so on. However, experimentally identifying such a phase transition is extremely challenging because the hidden from experimental probes. Here, using zero-field muon spin relaxation (ZF-$μ$SR) technique, we observe strong TRSB signals below 70 K newly...
We used a BACI (before-after-control-impact) experimental design to examine the effects of increasing winter habitat on abundance downstream migrant salmonids. Two reference streams and two treatment were selected in Alsea Nestucca basins Oregon. Population parameters for juvenile coho salmon (Oncorhynchus kisutch), age-0 trout spp.), steelhead mykiss), coastal cutthroat clarki) estimated each year 8 years stream. Stream was modified increase quality quantity during summers 1990 (Nestucca...
Accurate determination of the transient electronic structures, which drive photochemical reactions, is crucial in chemistry and biology. We report detection chemical changes on picosecond time scale by x-ray-absorption near-edge structure photoexcited aqueous [Ru(bpy)(3)](2+). Upon ultrashort laser pulse excitation a charge transfer excited state having 300 ns lifetime formed. detect change oxidation central Ru atom at its L3 L2 edges, temporal resolution 100 ps with zero unambiguously determined.
We have measured the excitation spectrum of six micron magnetic squares using x-ray circular dichroism. observe all three excitations expected in a Landau flux-closure pattern. High temporal and spatial resolution allows quantitative analysis excitations. A short plane pulse excites element we precessional motion magnetization within domains as well domain wall mode vortex motion. The moves perpendicular to field relaxes without showing circulating orbit.
We evaluated the effectiveness of using hatchery coho salmon (Oncorhynchus kisutch) presmolts to rebuild wild populations in Oregon coastal streams. Juvenile and adult were monitored 15 stocked unstocked streams from summer 1980 until 1985. During summers following planting presmolts, number juveniles per square metre pool surface area was higher than However, significantly less abundant during 2 yr when density estimated separately juveniles. Adult returns not different streams, but tended...
Mark-recapture, removal, and snorkel population estimates were compared with a known number of juvenile coho salmon Oncorhynchus kisutch stocked in 18 pools the same stream during summer. The effects fish density, pool size, habitat complexity on percentage actual estimated by three methods examined. Mark–recapture also numbers six winter, counts mark–recapture obtained other Oregon coastal streams summer winter. After all sizes densities combined, 85% present accounted for mark–recapture,...
We use femtosecond x-ray diffraction to probe directly the structural dynamics of a charge ordered and orbitally thin film ${\mathrm{La}}_{0.42}{\mathrm{Ca}}_{0.58}{\mathrm{MnO}}_{3}$ initiated by an ultrafast optical pulse. At low excitation fluences we observe displacive coherent ${A}_{g}$ phonon. Under high conditions complete phase transition within 1 ps via disappearance superlattice reflection. The initial step occurs on time scale significantly faster than 200 fs resolution our experiment.