A5034119362- Laser-Matter Interactions and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced X-ray Imaging Techniques
- ZnO doping and properties
- Spectroscopy and Quantum Chemical Studies
- Advanced Chemical Physics Studies
- Advanced Fiber Laser Technologies
- Quantum Dots Synthesis And Properties
- Atomic and Molecular Physics
- X-ray Diffraction in Crystallography
- Laser-Plasma Interactions and Diagnostics
- Photochemistry and Electron Transfer Studies
- Perovskite Materials and Applications
- Crystallization and Solubility Studies
- Electron and X-Ray Spectroscopy Techniques
- Ga2O3 and related materials
- Mass Spectrometry Techniques and Applications
- CO2 Reduction Techniques and Catalysts
- Metal-Catalyzed Oxygenation Mechanisms
- Advanced NMR Techniques and Applications
- Electrocatalysts for Energy Conversion
- Magnetism in coordination complexes
- Superconducting Materials and Applications
- Crystallography and Radiation Phenomena
- Nuclear Physics and Applications
Argonne National Laboratory
2014-2023
Pacific Northwest National Laboratory
2023
Physical Sciences (United States)
2023
Universidad Autónoma de Madrid
2023
HUN-REN Wigner Research Centre for Physics
2023
Hungarian Academy of Sciences
2023
Environmental Molecular Sciences Laboratory
2023
Technical University of Denmark
2017
Stony Brook University
2007-2010
The Ohio State University
2007-2009
The “hole” story of water ionization direct observation the cationic hole H 2 O + that is formed in liquid after has been a long-standing experimental challenge. Previous attempts using optical and ultraviolet techniques have failed to reveal its key spectroscopic signature during ultrafast transformation into OH radical. Loh et al. address this gap by intense, x-ray pulses from an free electron laser at ∼530 volts. They found compelling evidence for formation decay radical proton transfer...
The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser linac-based x-ray laser. Transient molecular nitrogen alignment revival features were resolved in time-dependent x-ray-induced fragmentation spectra. These find temporal overlap pump probe pulses. strong-field dissociation generated quasi-bound dications was establish...
The Linac Coherent Light Source free electron laser is a source of high brightness x rays, 2×1011 photons in ∼5 fs pulse, that can be focused to produce double core vacancies through rapid sequential ionization. This enables vacancy Auger spectroscopy, an entirely new way study femtosecond chemical dynamics with electrons probe the local valence structure molecules near specific atomic core. Using 1.1 keV for x-ray ionization impulsively aligned molecular nitrogen, we observed rich...
We show that high fluence, high-intensity x-ray pulses from the world's first hard free-electron laser produce nonlinear phenomena differ dramatically linear x-ray-matter interaction processes are encountered at synchrotron sources. use intense of sub-10-fs duration to reveal and subsequently drive 1s↔2p resonance in singly ionized neon. This photon-driven cycling an inner-shell electron modifies Auger decay process, as evidenced by line shape modification. Our work demonstrates propensity...
Nanostructures of transition metal oxides, such as zinc oxide, have attracted considerable interest for solar-energy conversion and photocatalysis. Both applications are sensitive to the transport trapping photoexcited charge carriers. The probing electron has recently become possible using time-resolved element-sensitive methods, X-ray spectroscopy. However, valence-band-trapped holes so far escaped observation. Herein we use absorption spectroscopy combined with a dispersive emission...
X-ray transient absorption spectroscopy (X-TAS) has been used to study the light-induced hydrogen evolution reaction catalyzed by a tetradentate macrocyclic cobalt complex with formula [LCo(III)Cl2](+) (L = ligand), [Ru(bpy)3](2+) photosensitizer, and an equimolar mixture of sodium ascorbate/ascorbic acid electron donor in pure water. near edge structure (XANES) extended fine (EXAFS) analysis binary octahedral Co(III) precatalyst after illumination revealed situ formation Co(II) intermediate...
A series of highly luminescent europium(III) complexes which exhibit photoluminescence from the Eu(III) center following energy transfer UV absorbing organic sensitizer have been investigated using a combination ultrafast optical transient absorption and Eu L3 X-ray techniques. We previously demonstrated that latter can be used as signature 4f–4f excitation responsible for in these coordination complexes, but long time scale earlier measurements did not allow direct observation...
We report the compression of intense, carrier-envelope phase stable mid-IR pulses down to few-cycle duration using an optical filament. A filament in xenon gas is formed by self-phase stabilized 330 μJ 55 fs at 2 μm produced via difference-frequency generation a Ti:sapphire-pumped parametric amplifier. The ultrabroadband carrier-wavelength output self-compressed below 3 cycles and has 270 pulse energy. self-locked offset field preserved after filamentation. This our knowledge first...
We describe our implementation of a high repetition rate (54 kHz–6.5 MHz), power (>10 W), laser system at the 7ID beamline Advanced Photon Source for pump/x-ray probe studies optically driven molecular processes. Laser pulses 1.06 μm wavelength and variable duration (10 or 130 ps) are synchronized to storage ring rf signal precision ∼250 fs rms. Frequency doubling tripling radiation using nonlinear optical techniques have been applied generate 532 355 nm light. demonstrate that by...
Theoretical predictions show that depending on the populations of Fe 3d xy , xz and yz orbitals two possible quintet states can exist for high-spin state photoswitchable model system [Fe(terpy)2]2+. The differences in structure molecular properties these 5B2 5E quintets are very small pose a substantial challenge experiments to resolve them. Yet better understanding physics this system, which lead design novel molecules with enhanced photoswitching performance, it is vital determine reached...
The development of next-generation perovskite-based optoelectronic devices relies critically on the understanding interaction between charge carriers and polar lattice in out-of-equilibrium conditions. While it has become increasingly evident for CsPbBr3 perovskites that Pb–Br framework flexibility plays a key role their light-activated functionality, corresponding local structural rearrangement not yet been unambiguously identified. In this work, we demonstrate photoinduced changes system...
Resonant inelastic x-ray scattering (RIXS) provides remarkable opportunities to interrogate ultrafast dynamics in liquids. Here we use RIXS study the fundamentally and practically important hydroxyl radical liquid water, OH(aq). Impulsive ionization of pure water produced a short-lived population OH(aq), which was probed using femtosecond x-rays from an free-electron laser. We find that reveals localized electronic transitions are masked ultraviolet absorption spectrum by strong...
We present a joint experimental and computational study of the hexacyanoferrate aqueous complexes at equilibrium in 250 meV to 7.15 keV regime. The experiments computations include vibrational spectroscopy cyanide ligands, valence electronic absorption spectra, Fe 1s core hole spectra using element-specific-resonant X-ray emission techniques. Density functional theory-based quantum mechanics/molecular mechanics molecular dynamics simulations are performed generate explicit solute-solvent...
X-ray spectroscopies, when combined in laser-pump, X-ray-probe measurement schemes, can be powerful tools for tracking the electronic and geometric structural changes that occur during course of a photoinitiated chemical reaction. absorption spectroscopy (XAS) is considered an established technique such measurements, emission (XES) strongest core-to-core lines (Kα Kβ) now being utilized. Flux demanding valence-to-core XES promises to important addition time-resolved spectroscopic toolkit. In...
We have employed a range of ultrafast X-ray spectroscopies in an effort to characterize the lowest energy excited state [Fe(dcpp)2]2+ (where dcpp is 2,6-(dicarboxypyridyl)pyridine). This compound exhibits unusually short excited-state lifetime for low-spin Fe(II) polypyridyl complex 270 ps room-temperature fluid solution, raising questions as whether ligand-field strength had pushed this system beyond 5T2/3T1 crossing point and stabilizing latter state. Kα Kβ emission been used unambiguously...
Abstract A narrow bandwidth x-ray beamline and a multi-crystal von Hamos spectrometer were used to record absorption emission (XES) across the uranium L 3 edge of UO 2 , Cs Cl 4 UCl 6 . Measurements made over 17150–17250 eV with an instrumental resolution ∼2 eV. This allowed use Lorentzian peak fits <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>L</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:mi>N</mml:mi> <mml:mn>4</mml:mn>...
We probe the dynamics of valence electrons in photoexcited [Fe(terpy)2]2+ solution to gain deeper insight into Fe–ligand bond changes. use hard X-ray emission spectroscopy (XES), which combines element specificity and high penetration with sensitivity orbital structure, making it a powerful technique for molecular studies wide variety environments. A picosecond-time-resolved measurement complete 1s spectrum captures transient photoinduced changes includes weak valence-to-core (vtc) lines...
Ligand substitution reactions are common in solvated transition metal complexes, and harnessing them through initiation with light promises interesting practical applications, driving interest new means of probing their mechanisms. Using a combination time-resolved x-ray absorption spectroscopy hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations near-edge calculations, we elucidate the mechanism photoaquation model system iron(ii) hexacyanide, where UV...
Here we present the first angle-resolved, non-resonant (normal) Auger spectra for impulsively aligned nitrogen molecules. We have measured angular pattern of electron emission following K-shell photoionization by 1.1 keV photons from Linac Coherent Light Source (LCLS). Using strong-field-induced molecular alignment to make frame measurements is equally effective both repulsive and quasi-bound final states. The capability resolve distributions in reference provides a new tool spectral...
The capability of generating two intense, femtosecond x-ray pulses with controlled time delay opens the possibility performing time-resolved experiments for induced phenomena. We have applied this to study photoinduced dynamics in diatomic molecules. In molecules composed low-Z elements, \textit{K}-shell ionization creates a core-hole state which main decay mode is an Auger process involving electrons valence shell. After decay, nuclear wavepackets transient two-valence-hole states continue...
The evolution of charge carriers in photoexcited room temperature ZnO nanoparticles solution is investigated using ultrafast ultraviolet photoluminescence spectroscopy, Zn K-edge absorption and ab initio molecular dynamics (MD) simulations. excited at 4.66 eV, well above the band edge, shows that electron cooling conduction exciton formation occur &lt;500 fs, excellent agreement with theoretical predictions. x-ray measurements, obtained upon excitation close to edge 3.49 are sensitive...