A5044201792- Laser-Matter Interactions and Applications
- Atomic and Molecular Physics
- Advanced Chemical Physics Studies
- Advanced X-ray Imaging Techniques
- Mass Spectrometry Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Quantum optics and atomic interactions
- Laser-Plasma Interactions and Diagnostics
- Coagulation, Bradykinin, Polyphosphates, and Angioedema
- Nuclear Physics and Applications
- Spectroscopy and Quantum Chemical Studies
- Nuclear physics research studies
- Ion-surface interactions and analysis
- Blood Coagulation and Thrombosis Mechanisms
- Venous Thromboembolism Diagnosis and Management
- Advanced Electron Microscopy Techniques and Applications
- Photochemistry and Electron Transfer Studies
Goethe University Frankfurt
2018-2024
Heinrich Heine University Düsseldorf
1996
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....
We report on the non-adiabatic offset of initial electron momentum distribution in plane polarization upon single ionization argon by strong field tunneling and show how to experimentally control degree non-adiabaticity. Two-color counter- co-rotating fields (390 780 nm) are compared that strongly depends temporal evolution laser electric field. introduce a simple method for direct access using two-color fields. Further, single-color circularly polarized at nm we radius observed donut-like...
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...
A central motivation for the development of x-ray free-electron lasers has been prospect time-resolved single-molecule imaging with atomic resolution. Here, we show that photoelectron diffraction—where a emitted after absorption illuminates molecular structure from within—can be used to image increase internuclear distance during x-ray-induced fragmentation an O2 molecule. By measuring molecular-frame emission patterns two-photon sequential K-shell ionization in coincidence fragment ions,...
The ultrafast structural dynamics of water following inner-shell ionization is a crucial issue in high-energy radiation chemistry. We have exposed isolated molecules to short x-ray pulse from free-electron laser and detected momenta all produced ions coincidence. By combining experimental results theoretical modeling, we can image dissociation individual unprecedented detail. reveal significant molecular H2O2+, such as asymmetric deformation bond-angle opening, leading two-body or three-body...
Photoionization is one of the fundamental light-matter interaction processes in which absorption a photon launches escape an electron. The time scale this process poses many open questions. Experiments have found delays attosecond (10-18 seconds) domain between electron ejection from different orbitals, electronic bands, or directions. Here, we demonstrate that, across molecular orbital, not launched at same time. Rather, birth depends on travel molecule, 247 zeptoseconds (1 zeptosecond =...
We experimentally investigate the effects of linear photon momentum on distributions photoions and photoelectrons generated in one-photon ionization an energy range 300 eV≤Eγ≤40 keV. Our results show that for each event is imparted onto photoion, which essentially system's center mass. Nevertheless, mean value ion distribution along light propagation direction backward-directed by −3/5 times momentum. These confirm a 90-year-old prediction.Received 30 March 2020Revised 5 May 2020Accepted 8...
We report on a multiparticle coincidence experiment performed at the European X-ray Free-Electron Laser Small Quantum Systems instrument using COLTRIMS reaction microscope. By measuring two ions and electrons in coincidence, we investigate double core-hole generation O_{2} molecules gas phase. Single-site two-site core holes have been identified their molecular-frame electron angular distributions obtained for breakup of oxygen molecule into doubly charged ions. The measured are compared to...
The recent implementation of attosecond and few-femtosecond X-ray pump/X-ray probe schemes in large-scale free-electron laser facilities has opened the way to visualize fast nuclear dynamics molecules with unprecedented temporal spatial resolution. Here, we present results theoretical calculations showing how polarization-averaged molecular-frame photoelectron angular distributions (PA-MFPADs) can be used hydrogen migration methanol, ethanol, propanol, isopropyl alcohol dications generated...
We experimentally study the influence of binding energy on nondipole effects in $K$-shell single-photon ionization atoms at high photon energies. find that for each event, as expected by momentum conservation, is transferred almost fully to recoiling ion. The distribution electrons becomes asymmetrically deformed along propagation direction with a mean value $8/(5c)({E}_{\ensuremath{\gamma}}\ensuremath{-}{I}_{P})$ confirming an 100 year old prediction Sommerfeld and Schur [Ann. Phys. (N.Y.)...
We investigate angular emission distributions of the $1s$ photoelectrons ${\mathrm{N}}_{2}$ ionized by linearly polarized synchrotron radiation at $h\ensuremath{\nu}=40\text{ }\text{ }\mathrm{keV}$. As expected, nondipole contributions cause a very strong forward-backward asymmetry in measured distributions. In addition, we observe an unexpected with respect to polarization direction, which depends on direction molecular fragmentation. particular, are predominantly emitted forward nitrogen...
We investigate $K$-shell ionization of ${\mathrm{N}}_{2}$ at 40 keV photon energy. Using a cold target recoil ion momentum spectroscopy reaction microscope, we determine the vector momenta photoelectron, Auger electron, and both ${\mathrm{N}}^{+}$ fragments. These fully differential data show that dissociation process ${\mathrm{N}}_{2}^{2+}$ is significantly modified not only by photoelectron but also emitted electron. find energy introduced partitioned with ratio approximately...
Abstract We investigate experimentally and theoretically the N 1s photoionization of fixed-in-space 2 molecules at a photon energy 880 eV. In our experiment, we employed circularly polarized synchrotron radiation for coincident electron fragment-ion detection using cold target recoil ion momentum spectroscopy. The accompanying angle-resolved calculations were carried out by multichannel single-center method code within frozen-core Hartree–Fock approximation. computed emission distributions...
We investigate experimentally and theoretically the C O 1s photoionization of fixed-in-space CO molecules at a photon energy 905 eV. find significant dependence photoelectron angular distributions on direction propagation ionizing radiation. It results from an interplay nondipole effects, one hand, molecular other. The effects lead to increase emission probability in forward along light propagation, wave being scattered by potential gives rise strong peak atom neighboring emitter site. These...
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 ${\mathrm{CH}}_{3}\mathrm{I}$...
This work studies quasifree double photoionization using reaction microscopy and companion $a\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ calculations. The mechanism is confirmed for H${}_{2}$ introduced as a probe the electron-electron cusp density in ground state of two-electron target.
During the last decade, X-ray free-electron lasers (XFELs) have enabled study of light-matter interaction under extreme conditions. Atoms which are subject to XFEL radiation charged by a complex interplay (several subsequent) photoionization events and electronic decay processes within few femtoseconds. The with molecules is even more intriguing, since intricate nuclear dynamics occur as start dissociate during charge-up process. Here, we demonstrate that analyzing photoelectron angular...
We show that the combination of two achiral components - atomic or molecular target plus a circularly polarized photon can yield chirally structured photoelectron angular distributions. For photoionization CO, distribution carbon K-shell photoelectrons is chiral when axis neither perpendicular nor (anti-)parallel to light propagation axis. In photo-double-ionization He, one electron chiral, if other oriented like in former case and electrons are distinguishable by their energy. both...
We report a fully differential study of ionization the Ne L shell by Compton scattering 20 keV photons. find two physical mechanisms that modify Compton-electron emission. Firstly, we observe electrons at their parent nucleus. Secondly, distinct maximum in electron momentum distribution close-to-zero attribute to focusing Coulomb potential.
We experimentally investigated the quasifree mechanism (QFM) in one-photon double ionization of He and H2 at 800 eV photon energy circular polarization with a COLTRIMS reaction microscope. Our work provides new insight into this elusive photoionization that was predicted by Miron Amusia more than four decades ago. found distinct four-fold symmetry angular emission pattern QFM electrons from has previously only been observed for He. Furthermore, we provide experimental evidence momentum is...