A5004816010- Laser-Matter Interactions and Applications
- Mass Spectrometry Techniques and Applications
- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Atomic and Molecular Physics
- Spectroscopy and Laser Applications
- Advanced Fiber Laser Technologies
- Advanced X-ray Imaging Techniques
- Advanced Electron Microscopy Techniques and Applications
- Ion-surface interactions and analysis
- Cold Atom Physics and Bose-Einstein Condensates
- Photonic and Optical Devices
- Laser-Plasma Interactions and Diagnostics
- Photochemistry and Electron Transfer Studies
- Laser Design and Applications
- Nuclear Physics and Applications
- Particle Detector Development and Performance
- Molecular Junctions and Nanostructures
- X-ray Spectroscopy and Fluorescence Analysis
- Astrophysics and Star Formation Studies
- Molecular Spectroscopy and Structure
- Various Chemistry Research Topics
- Molecular spectroscopy and chirality
- Quantum Information and Cryptography
- Photoreceptor and optogenetics research
Deutsches Elektronen-Synchrotron DESY
2015-2025
Center for Free-Electron Laser Science
2016-2025
Max Planck Institute for the Structure and Dynamics of Matter
2016-2025
Universität Hamburg
2016-2025
Goethe University Frankfurt
2022
University of Chemistry and Technology, Prague
2022
Jilin University
2022
Fritz Haber Institute of the Max Planck Society
2022
Hamburg Centre for Ultrafast Imaging
2019
University of Oxford
2018
Anion-molecule nucleophilic substitution (S(N)2) reactions are known for their rich reaction dynamics, caused by a complex potential energy surface with submerged barrier and weak coupling of the relevant rotational-vibrational quantum states. The dynamics S(N)2 Cl- + CH3I were uncovered in detail using crossed molecular beam imaging. As function collision energy, transition from complex-mediated mechanism to direct backward scattering I- product was observed experimentally. Chemical...
Tightly tracking charge migration Electron transfer dynamics underlie many chemical and biochemical reactions. Erk et al. examined the between individual carbon iodine atoms during dissociation of iodomethane (ICH 3 ) molecules (see Perspective by Pratt). After initiating scission C-I bond with a relatively low-energy laser pulse, they introduced higher-energy x-ray pulse to instigate ionization migration. Delaying arrival time effectively varied separation distance being probed as fragments...
Ionization and fragmentation of methylselenol (CH(3)SeH) molecules by intense (>10(17) W/cm(2)) 5 fs x-ray pulses (ħω=2 keV) are studied coincident ion momentum spectroscopy. We contrast the measured charge state distribution with data on atomic Kr, determine kinetic energies resulting ionic fragments, compare them to outcome a Coulomb explosion model. find signatures ultrafast redistribution from inner-shell ionized Se atom its molecular partners, observe significant displacement...
The highly exoergic nucleophilic substitution reaction F– + CH3I shows dynamics strikingly different from that of reactions larger halogen anions. Over a wide range collision energies, large fraction indirect scattering via long-lived hydrogen-bonded complex is found both in crossed-beam imaging experiments and direct chemical simulations. Our measured differential cross sections show large-angle low product velocities for all resulting efficient transfer the energy to internal CH3F product....
The understanding of molecular structure and function is at the very heart chemical sciences. Experiments that allow for creation structurally pure samples investigation their dynamics have developed tremendeously over last few decades, although 'there's plenty room bottom' better control as well further applications. Here, we describe use inhomogeneous electric fields manipulation neutral molecules in gas-phase, i.e. separation complex according to size, structural isomer, quantum state....
Recording molecular movies on ultrafast timescales has been a longstanding goal for unravelling detailed information about dynamics. Here we present the direct experimental recording of very-high-resolution and -fidelity over more than one-and-a-half periods laser-induced rotational dynamics carbonylsulfide (OCS) molecules. Utilising combination single quantum-state selection an optimised two-pulse sequence to create tailored wavepacket, unprecedented degree field-free alignment, 〈cos2θ2D〉 =...
Ion imaging experiments and direct chemical dynamics simulations were performed to study the atomic-level for F− + CH3I → FCH3 I− SN2 nucleophilic substitution reaction at 0.32 eV collision energy. The reproduce product energy partitionings velocity scattering angle distribution measured in experiments. reveal that occurs by two mechanisms, is, rebound stripping, an indirect mechanism. Approximately 90% of events occur via a prereaction F−···HCH2I hydrogen-bonded complex. This mechanism may...
We demonstrate an experimental method to record snapshot diffraction images of polyatomic gas-phase molecules, which can, in a next step, be used probe time-dependent changes the molecular geometry during photochemical reactions with femtosecond temporal and angstrom spatial resolution. Adiabatically laser-aligned 1-ethynyl-4-fluorobenzene (C${}_{8}$H${}_{5}$F) molecules were imaged by photoelectrons kinetic energies between 31 62 eV, created from core ionization fluorine ($1s$) level...
Ultrafast electron transfer in dissociating iodomethane and fluoromethane molecules was studied at the Linac Coherent Light Source free-electron laser using an ultraviolet-pump, X-ray-probe scheme. The results for both are discussed with respect to nature of their UV excitation different chemical properties. Signatures long-distance intramolecular charge observed species, a quantitative analysis its distance dependence is carried out states up I21+. reconstructed critical distances good...
Abstract Polycyclic aromatic hydrocarbons (PAHs) play an important role in interstellar chemistry and are subject to high energy photons that can induce excitation, ionization, fragmentation. Previous studies have demonstrated electronic relaxation of parent PAH monocations over 10–100 femtoseconds as a result beyond-Born-Oppenheimer coupling between the nuclear dynamics. Here, we investigate three molecules: fluorene, phenanthrene, pyrene, using ultrafast XUV IR laser pulses. Simultaneous...
We illustrate, experimentally and theoretically, a laser-based method to control the rotations of polyatomic molecules in 3D space. A linearly polarized nanosecond pulse strongly aligns most polarizable axis an asymmetric top molecule along its polarization while orthogonally polarized, femtosecond sets into controlled rotation about aligned axis. As result, strong three-dimensional (3D) alignment occurs shortly after is repeated periodically, reflecting coherent revolution molecular Our...
The sequential inner-shell multiple ionization of krypton was investigated at the Linac Coherent Light Source using ion time-of-flight spectroscopy photon energies above (2 keV) and below (1.5 $L$ edge with two x-ray pulse lengths (5 80 fs, nominally) various energies. At 2.5 mJ energy, charge states up to Kr${}^{17+}$ were recorded for $M$-shell Kr${}^{21+}$ $L$-shell ionization. Comparing experimental state distribution Monte Carlo rate-equation calculations, we find a strong enhancement...
We present a study of the different product channels in reactions OH− and OH−(H2O) with methyl iodide over range collision energies. Direct dynamics classical trajectory simulations are employed to obtain an atomistic comparison experimental results. For experiments we have combined crossed beam ion imaging setup multipole rf trap. The trap allows us prepare molecular cluster ions controlled internal temperature thus provides well-defined initial conditions for reaction at low energy....
This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and X-ray free-electron laser. We present results two experiments aimed at measuring angular distributions laser-aligned 1-ethynyl-4-fluorobenzene (C(8)H(5)F) dissociating, 1,4-dibromobenzene (C(6)H(4)Br(2)) discuss them the larger context molecules. also show how strong nanosecond laser pulse used for...
The dynamics following laser-induced molecular photodissociation of gas-phase ${\mathrm{CH}}_{2}\mathrm{BrI}$ at 271.6 nm were investigated by time-resolved Coulomb-explosion imaging using intense near-IR femtosecond laser pulses. observed delay-dependent photofragment momenta reveal that undergoes C-I cleavage, depositing 65.6% the available energy into internal product states, and absorption a second UV photon breaks C-Br bond ${\mathrm{CH}}_{2}\mathrm{Br}$. Simulations confirm this...
The photodissociation dynamics of CH3I and CH2ClI at 272 nm were investigated by time-resolved Coulomb explosion imaging, with an intense non-resonant 815 probe pulse. Fragment ion momenta over a wide m/z range recorded simultaneously coupling velocity map imaging spectrometer pixel mass spectrometry camera. For both molecules, delay-dependent pump-probe features assigned to ultraviolet-induced carbon-iodine bond cleavage followed explosion. Multi-mass also allowed the sequential...
Due to its element- and site-specificity, inner-shell photoelectron spectroscopy is a widely used technique probe the chemical structure of matter. Here we show that time-resolved can be employed observe ultrafast reactions electronic response nuclear motion with high sensitivity. The ultraviolet dissociation iodomethane (CH$_3$I) investigated by ionization above iodine 4d edge, using photoion spectroscopy. dynamics observed in spectra appear earlier are faster than those seen fragments....
We explore time-resolved Coulomb explosion induced by intense, extreme ultraviolet (XUV) femtosecond pulses from the FLASH free-electron laser as a method to image photo-induced molecular dynamics in two molecules, iodomethane and 2,6-difluoroiodobenzene. At an excitation wavelength of 267\,nm, dominant reaction pathway both molecules is neutral dissociation via cleavage carbon--iodine bond. This allows investigating influence environment on absorption XUV pulse subsequent process. find that...
We report on a new versatile transportable endstation for controlled molecule (eCOMO) experiments providing combination of molecular beam purification by electrostatic deflection and simultaneous ion electron detection using velocity-map imaging (VMI). The b-type deflector provides spatial dispersion species based their effective-dipole-moment-to-mass ratio. This enables selective investigation rotational quantum states, conformers, clusters. Furthermore, the double-sided VMI spectrometer...
We have studied the negative ion reaction ${\mathrm{NH}}_{2}^{\ensuremath{-}}+{\mathrm{H}}_{2}\ensuremath{\rightarrow}{\mathrm{NH}}_{3}+{\mathrm{H}}^{\ensuremath{-}}$ in temperature range from 300 to 8 K. observe a strongly suppressed probability for proton transfer at room temperature. With decreasing temperature, this increases, accordance with longer lifetime of an intermediate anion-neutral complex. At low temperatures, maximum rate coefficient is observed that suggests presence very...
Absolute photodetachment cross sections have been measured for the hydrocarbon chain anions CnH−, n = 2, 4, and 6, which are relevant an understanding of molecular clouds in interstellar medium. Data obtained different photon energies within approximately 1 eV detachment threshold. With our recently developed method we achieved a precision better than 25% on these absolute sections. The experiments carried out by means tomography mass-selected multipole radio-frequency ion trap. accordance...
We demonstrate strong adiabatic laser alignment and mixed-field orientation at kHz repetition rates. observe the degrees of as large ⟨cos2θ⟩2D=0.94 1 operation for iodobenzene. The experimental setup consists a system simultaneously producing pulses 30 fs (1.3 mJ) 450 ps (9 mJ). A cold 1-K state-selected molecular beam is produced same rate by appropriate an Even–Lavie valve. Quantum state selection has been obtained using electrostatic deflector. camera data acquisition records analyses...
The absolute photodetachment cross section of OH- anions at a rotational and translational temperature 170K is determined by measuring the detachment-induced decay rate in multipole radio-frequency ion trap. In comparison with previous results, obtained shows importance initial state distribution. Using tomography scan laser through trapped cloud, derived model-independent thus features small systematic uncertainty. also yields column density 22-pole trap good agreement expected trapping...
We demonstrate the spatial separation of prototypical indole(H${}_{2}$O) clusters from various species present in supersonic expansion mixtures indole and water. The major molecular constituents resulting beam are H${}_{2}$O, indole, indole(H${}_{2}$O), indole(H${}_{2}$O)${}_{2}$. It is a priori not clear whether such floppy systems amenable to strong manipulation using electric fields. Here, we have exploited cold electrostatic deflector separate other as well helium seed gas. experimental...