A5009724840- Laser-Matter Interactions and Applications
- Atomic and Molecular Physics
- Advanced Chemical Physics Studies
- Mass Spectrometry Techniques and Applications
- Laser-Plasma Interactions and Diagnostics
- Nuclear physics research studies
- Spectroscopy and Quantum Chemical Studies
- Advanced X-ray Imaging Techniques
- X-ray Spectroscopy and Fluorescence Analysis
- Ion-surface interactions and analysis
- Electron and X-Ray Spectroscopy Techniques
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Fiber Laser Technologies
- Laser Design and Applications
- Quantum optics and atomic interactions
- Photocathodes and Microchannel Plates
- Analytical Chemistry and Sensors
- Advanced Chemical Sensor Technologies
- Quantum Information and Cryptography
- Molecular spectroscopy and chirality
- Molecular Junctions and Nanostructures
- Gas Sensing Nanomaterials and Sensors
- Astro and Planetary Science
- Advanced Biosensing Techniques and Applications
- Atomic and Subatomic Physics Research
Goethe University Frankfurt
2015-2024
Goethe Institute
2024
Lawrence Berkeley National Laboratory
2014-2015
Fraunhofer Society
2011
Fraunhofer Institute for Physical Measurement Techniques
2011
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 nonsequential double ionization of Ar by a laser pulse consisting two counterrotating circularly polarized fields (390 and 780 nm). The double-ionization probability depends strongly the relative intensity shows kneelike structure as function intensity. conclude that is driven beam nearly monoenergetic recolliding electrons, which can be controlled in energy field parameters. electron momentum distributions show well second escapes from an intermediate excited state Ar^{+}.
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...
Most large molecules are chiral in their structure: they exist as two enantiomers, which mirror images of each other. Whereas the rovibronic sublevels enantiomers almost identical (neglecting a minuscular effect weak interaction), it turns out that photoelectric is sensitive to absolute configuration ionized enantiomer. Indeed, photoionization randomly oriented by left or right circularly polarized light results slightly different electron flux parallel antiparallel with respect photon...
Even though ion/atom-collision is a mature field of atomic physics great discrepancies between experiment and theoretical calculations are still common. Here we present experimental results with highest momentum resolution on single ionization helium induced by 1\,MeV protons compare these to different calculations. The overall agreement strikingly good already the first Born approximation yields theory experiment. This has been expected since several decades, but so far not accomplished....
Strong-field ionization of atoms by circularly polarized femtosecond laser pulses produces a donut-shaped electron momentum distribution. Within the dipole approximation this distribution is symmetric with respect to polarization plane. The magnetic component light field known shift forward. Here, we show that nondipole effect not only in strong-field ionization. We find an electric arises due position dependence and which can be understood analogy Doppler effect. This manifests as increase...
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...
We report on three-dimensional (3D) electron momentum distributions from single ionization of helium by a laser pulse consisting two counterrotating circularly polarized fields (390 nm and 780 nm). A pronounced 3D low energy structure sub-cycle interferences are observed experimentally reproduced numerically using trajectory based semi-classical simulation. The orientation the in polarization plane is verified numerical simulations solving time dependent Schr\"odinger equation.
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,...
If matter absorbs a photon of sufficient energy it emits an electron. The question the duration emission process has intrigued scientists for decades. With advent attosecond metrology, experiments addressing such ultrashort intervals became possible. While these types studies require experimental precision, we present here novel measurement approach that avoids those difficulties. We instead extract delay from interference pattern generated as emitted photoelectron is diffracted by parent...
We report on a joint experimental and theoretical study of photoelectron circular dichroism (PECD) in methyloxirane. By detecting O 1s-photoelectrons coincidence with fragment ions, we deduce the molecule's orientation emission direction laboratory frame. Thereby, retrieve fourfold differential PECD clearly beyond 50%. This strong chiral asymmetry is reproduced by ab initio electronic structure calculations. Providing such pronounced contrast makes fixed-in-space molecules an even more...
We experimentally and theoretically investigate the influence of magnetic component an electromagnetic field on high-order above-threshold ionization xenon atoms driven by ultrashort femtosecond laser pulses. The nondipole shift electron momentum distribution along light-propagation direction for high energy electrons beyond 2U_{p} classical cutoff is found to be vastly different from that below this cutoff, where U_{p} ponderomotive potential driving field. A local minimum structure in...
Chirality is omnipresent in living nature. On the single molecule level, response of a chiral species to probe depends on their respective handedness. A prominent example difference interaction with left or right circularly polarized light. In present study, we show by Coulomb explosion imaging that light can also induce fragmentation planar and thus achiral molecule. The observed enantiomer strongly orientation respect propagation direction helicity ionizing This finding might trigger new...
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...
The photoelectric effect describes the ejection of an electron upon absorption one or several photons. kinetic energy this is determined by photon reduced binding and, if strong laser fields are involved, ponderomotive potential in addition. It has therefore been widely taken for granted that atoms and molecules, photoelectron does not depend on electron’s emission direction, but theoretical studies have questioned since 1990. Here, we provide experimental evidence energies photoelectrons...
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...
We investigate the differential ionization probability of chiral molecules in strong field regime as a function helicity incident light. To this end, we analyze fourfold bromochlorofluoromethane (CHBrClF) with subsequent fragmentation into four charged fragments and different dissociation channels singly ionized methyloxirane. observe variation range several percent. Accordingly, conclude that light is quantity should be considered for theoretical description rate molecules.
We experimentally and theoretically show that the electron energy spectra strongly depend on relative helicity in highly intense, circularly polarized two-color laser fields, which is an unexpected finding. The employed counter-rotating (CRTC) fields corotating (CoRTC) are both a superposition of pulses at central wavelength 390 780 nm (intensity ratio ${I}_{390}/{I}_{780}\ensuremath{\approx}250)$. For CRTC field, measured spectrum dominated by peaks spaced 3.18 eV (corresponds to photon...
The influence of the magnetic component driving electromagnetic field is often neglected when investigating light-matter interaction. We show that light plays an important role in nonsequential double ionization, which serves as a powerful tool to investigate electron correlation. magnetic-field effects ionization xenon atoms driven by near-infrared ultrashort femtosecond laser pulses and find mean forward shift momentum distribution light-propagation direction agrees well with classical...
We present a study on molecular-frame photoelectron angular distributions (MFPADs) of small molecules using circularly polarized synchrotron light. find that the main forward-scattering peaks MFPADs are slightly tilted with respect to molecular axis. This tilt angle is directly connected bond length by simple, universal formula. apply derived formula several examples C 1s and O photoelectrons CO, which have been measured experimentally or obtained means ab initio modeling. In addition, we...
We report on a kinematically complete measurement of double ionization helium by single 1100 eV circularly polarized photon. By exploiting dipole selection rules in the two-electron continuum state, we observed angular emission pattern electrons originating from pure quadrupole transition. Our fully differential experimental data and companion ab initio nonperturbative theory show separation contributions to photo-double-ionization provide new insight into nature quasifree mechanism.