A5041760140- Laser-Matter Interactions and Applications
- Advanced X-ray Imaging Techniques
- Atomic and Molecular Physics
- Advanced Chemical Physics Studies
- Advanced Electron Microscopy Techniques and Applications
- Mass Spectrometry Techniques and Applications
- Laser-Plasma Interactions and Diagnostics
- Spectroscopy and Quantum Chemical Studies
- Particle Accelerators and Free-Electron Lasers
- X-ray Spectroscopy and Fluorescence Analysis
- Photochemistry and Electron Transfer Studies
- Ion-surface interactions and analysis
- Nuclear Physics and Applications
- Terahertz technology and applications
- Quantum Mechanics and Applications
- Quantum Information and Cryptography
- Photosynthetic Processes and Mechanisms
- Cold Atom Physics and Bose-Einstein Condensates
- Mechanical and Optical Resonators
- Photonic and Optical Devices
- Laser-induced spectroscopy and plasma
Max Planck Institute for Nuclear Physics
2017-2025
Heidelberg University
2023
Universität Ulm
2015
Abstract Following structural dynamics in real time is a fundamental goal towards better understanding of chemical reactions. Recording snapshots individual molecules with ultrashort exposure times key ingredient this goal, as atoms move on femtosecond (10 −15 s) timescales. For condensed-phase samples, ultrafast, atomically resolved structure determination has been demonstrated using X-ray and electron diffraction. Pioneering experiments have also started addressing gaseous samples....
Ultrashort x-ray pulses from free-electron lasers can efficiently charge up and trigger the full fragmentation of molecules. By coincident detection to five ions resulting rapid Coulomb explosion highly charged iodomethane, we show that three-dimensional equilibrium geometry this prototypical polyatomic system be determined measured ion momenta with help a buildup model. Supported by simulations how would reflect specific changes in molecular bond lengths angles, demonstrate...
Ultrafast H2+ and H3+ formation from ethanol is studied using pump-probe spectroscopy with an extreme ultraviolet (XUV) free-electron laser. The first pulse creates a dication, triggering H2 roaming that leads to formation, which disruptively probed by second pulse. At photon energies of 28 32 eV, the ratio increases time delay, while it flat at energy 70 eV. delay-dependent effect ascribed competition between electron proton transfer. High-level quantum chemistry calculations show potential...
We formulate a general hybrid quantum-classical technique to describe the interaction of diatomic molecules with XUV pulses. demonstrate accuracy our model in context <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi mathvariant="normal">O</a:mi><a:mn>2</a:mn></a:msub></a:math> molecule an pulse photon energy ranging from 20–42 eV. account for electronic structure and electron ionization quantum mechanically employing accurate molecular continuum wave functions. motion...
Upon ionization, water forms a highly acidic radical cation H2O+· that undergoes ultrafast proton transfer (PT)-a pivotal step in radiation chemistry, initiating the production of reactive H3O+, OH[Formula: see text] radicals, and (hydrated) electron. Until recently, time scales, mechanisms, state-dependent reactivity PT could not be directly traced. Here, we investigate dimers using time-resolved ion coincidence spectroscopy applying free-electron laser. An extreme ultraviolet (XUV) pump...
Photoionization can initiate structural reorganization of molecular matter and drive formation new chemical bonds. Here, we used time-resolved extreme ultraviolet (EUV) pump – EUV probe Coulomb explosion imaging carbon dioxide dimer ion $${\left({{{\rm{C}}}}{{{{\rm{O}}}}}_{2}\right)}_{2}^{+}$$ dynamics, that combined with ab initio dynamics simulations, revealed unexpected asymmetric rearrangement. We show ionization by the pulse induces rearrangement from slipped-parallel (C2h) geometry...
A reaction microscope dedicated to multi-particle coincidence spectroscopy on gas-phase samples is installed at beamline FL26 of the free-electron laser FLASH2 in Hamburg. The main goals instrument are follow dynamics atoms, molecules and small clusters their natural time-scale study non-linear light–matter interaction with such systems. To this end, combined an in-line extreme-ultraviolet (XUV) split-delay focusing optics, which allows time-resolved XUV-XUV pump–probe be performed.
Time delays for atomic photoemission obtained in streaking or reconstruction of attosecond bursts by interference two-photon transitions experiments originate from a combination the quantum mechanical Wigner time and Coulomb-laser coupling. While former was investigated intensively theoretically as well experimentally, latter attracted less interest has mostly been subject to calculations. Here, we present measurement coupling-induced shifts photoionization neon at 59.4 eV using terahertz...
Motivated by recent experiments in which a voltage-biased Josephson junction is placed series with resonator, the classical dynamics of circuit studied various domains parameter space. This problem can be mapped onto dissipative motion single degree freedom nonlinear time-dependent potential, where contrast to conventional settings nonlinearity appears driving while static potential purely harmonic. For long times system approaches steady states are analyzed underdamped regime over full...
High temporal resolution is essential for ultra-fast pump-probe experiments. Arrival time jitter and drift measurements, as well their control, become critical especially when combining XUV or X-ray free-electron lasers (FELs) with optical due to the large scale of such facilities distinct pulse generation processes. This paper presents application a laser arrival monitor that actively corrects an relative FEL’s main clock. Combined post-analysis single correction this new approach improves...
The electronic and nuclear dynamics inside molecules are essential for chemical reactions, where different pathways typically unfold on ultrafast timescales. Extreme ultraviolet (XUV) light pulses generated by free-electron lasers (FELs) allow atomic-site electronic-state selectivity, triggering specific molecular while providing femtosecond resolution. Yet, time-resolved experiments either blind to neutral fragments or limited the spectral bandwidth of FEL pulses. Here, we combine a...
The reaction microscope (REMI) endstation for atomic and molecular science at the free-electron laser FLASH2 DESY in Hamburg is presented together with a brief overview of results recently obtained. REMI allows coincident detection electrons ions that emerge from or fragmentation reactions focus extreme-ultraviolet (XUV) (FEL) beam. A large variety target species ranging atoms molecules to small clusters can be injected supersonic gas-jet into FEL focus. Their ionization dynamics studied...
A kinematically complete experiment on two-photon double ionization of Ar by free-electron laser radiation with a photon energy 27.93 eV was performed. The electron spectra show that is dominated the sequential process. Comparison angular distributions to our data for single and theory confirms even in process electrons from both steps are correlated each other through polarization intermediate $\mathrm{A}{\mathrm{r}}^{+}$ state. Furthermore, very important role autoionization found.
Abstract Ultrafast measurements in the extreme ultraviolet (XUV) spectral region targeting femtosecond timescales rely until today on two complementary XUV laser sources: free electron lasers (FELs) and high-harmonic generation (HHG) based sources. The combination of these source types was recently not realized. properties both sources including broad bandwidth, high pulse energy, narrowband tunability timing, open new opportunities for two-color pump-probe studies. Here we show first...
Extremely high charge states of atoms and molecules can be created when they are irradiated by intense x-ray pulses. At certain photon energies, electron ejection from drastically enhanced transient resonances during the sequential ionization process. Here we report on observation such resonance effects in a molecule, ${\mathrm{CH}}_{3}\mathrm{I}$, show photon-energy-dependent shift resonance-induced structures ion state distributions. By comparing distribution ${\mathrm{CH}}_{3}\mathrm{I}$...
Photoelectron emission from excited states of laser-dressed atomic helium is analyzed with respect to laser intensity-dependent excitation energy shifts and angular distributions. In the two-color XUV (exteme ultra\-violet) -- IR (infrared) measurement, photon scanned between \SI{20.4}{\electronvolt} ionization threshold at \SI{24.6}{\electronvolt}, revealing electric dipole-forbidden transitions for a temporally overlapping pulse ($\sim\!\SI{e12}{\watt\per \centi\meter\squared}$). The...
Charge transfer (CT) at avoided crossings of excited ionized states argon dimers is observed using a two-color pump-probe experiment the free-electron laser in Hamburg (FLASH). The process initiated by absorption three 27-eV-photons from pump pulse, which leads to population Ar2+*-Ar states. Due nonadiabatic coupling between these one-site doubly and two-site type Ar+*-Ar+, CT can take place leading latter onset this probed delayed infrared (800 nm) pulse. ionizes populating repulsive Ar2+...
We report the measurement of photoelectron angular distribution two-photon single-ionization near 2p^{2} ^{1}D^{e} double-excitation resonance in helium, benchmarking fundamental nonlinear interaction two photons with correlated electrons. This observation is enabled by unique combination intense extreme ultraviolet pulses, delivered at high-repetition-rate free-electron laser Hamburg (FLASH), ionizing a jet cryogenically cooled helium atoms reaction microscope. The spectral structure...
Abstract XUV multiphoton ionization of molecules is commonly used in free-electron laser experiments to study charge transfer dynamics. However, molecular dissociation and electron dynamics, such as multiple photon absorption, Auger decay, transfer, often happen on competing time scales, the contributions individual processes can be difficult unravel. We experimentally investigate Coulomb explosion dynamics methyl iodide upon core–hole shallow inner-shell iodine (4d) classically simulate...
The relaxation processes in atomic xenon following core ionization of the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>4</a:mn><a:mi>d</a:mi></a:mrow></a:math> and <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mn>4</b:mn><b:mi>p</b:mi></b:mrow></b:math> subshells by extreme ultraviolet (XUV) pulses from a free-electron laser (FLASH) are investigated using ion time-of-flight spectroscopy. We compare dynamics Auger-Meitner decays at 90-eV photon energy,...
We compute accurate potential energy curves of O$_2$ up to O$_2^{2+}$ for states that are energetically accessible in the photon range 20 42 eV. find dissociation limits these and atomic fragments which they dissociate. use Velocity Verlet algorithm account nuclear dynamics using computed curves. Through Monte Carlo simulations monitor motion electronic structure molecule, we obtain kinetic release distributions O$^+$ + exposed an XUV pulse range. compare theoretical with results obtained...
We present the design, integration, and operation of novel vacuum ultraviolet (VUV) beamline installed at free-electron laser (FEL) FLASH. The VUV source is based on high-order harmonic generation (HHG) in gas driven by an optical system synchronized with timing structure FEL. Ultrashort pulses spectral range from 10 to 40 eV are coupled FEL FL26, which features a reaction microscope (REMI) permanent endstation for time-resolved studies ultrafast dynamics atomic molecular targets. connection...
Abstract Ionization of laser-dressed atomic helium is investigated with focus on photoelectron angular distributions stemming from two-color multi-photon excited states. The experiment combines extreme ultraviolet (XUV) infrared (IR) radiation, while the relative polarization and temporal delay between pulses can be varied. By means an XUV photon energy scan over several electronvolts, we get access to states in dressed atom exhibiting various binding energies, momenta, magnetic quantum...
With a XUV-pump/THz-probe scheme the decay of excited O2 cations that were produced by irradiation with XUV photons has been investigated using Reaction Microscope (ReMi) at free-electron-laser FLASH in Hamburg. The temporal profile electrons emitted due to autoionization Rydberg states traced THz streaking. This way relaxation dynamics was followed. relative shift phase between photoelectrons and analyzed respect emission time delays or lifetimes.