Max Planck Advanced Study Group

Hamburg, Germany

Max Planck Advanced Study Group

Hamburg, Germany

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Saalmann U.,Max Planck Institute for the Physics of Complex Systems | Saalmann U.,Max Planck Advanced Study Group
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2010

Clusters exposed to intense laser radiation quickly turn into nanoplasmas: short-lived electron plasmas confined by the charged cluster ions on a nanometre scale. Although the cluster will eventually explode, the transient multi-electron dynamics during the pulse is of great interest and largely unexplored. It determines the mechanism of energy absorption and thus may help to understand measured electron and ion spectra, also in other samples, such as large molecules. Furthermore, an experimental setup with short pulses and access to observables, which becomes possible because of the sample's finite size, offers novel possibilities of investigating the non-equilibrium dynamics of plasmas. Here, the formation, excitation and relaxation of nanoplasmas in rare-gas clusters driven by strong pulses from free-electron lasers (FELs) with photon frequencies in the range of about 10 to 100 eV as currently available at FLASH are discussed. It is the unique combination of brilliant, tunable and short-pulse radiation in this machine and upcoming x-ray FELs which makes such studies feasible. © 2010 IOP Publishing Ltd.


Kastner A.,Max Planck Institute for the Physics of Complex Systems | Saalmann U.,Max Planck Institute for the Physics of Complex Systems | Saalmann U.,Max Planck Advanced Study Group | Rost J.M.,Max Planck Institute for the Physics of Complex Systems | Rost J.M.,Max Planck Advanced Study Group
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2012

Soft recollisions are laser-driven distant collisions of an electron with its parent ion. Such collisions may cause an energy bunching, since electrons with different initial drift momenta can acquire impulses which exactly counterbalance these differences. The bunching generates a series of peaks in the photo-electron spectrum. We will show that this series could be uncovered peak by peak experimentally by means of phase-stabilized few-cycle pulses with increasing duration. © 2012 IOP Publishing Ltd.


Kimberg V.,Max Planck Institute for the Physics of Complex Systems | Kimberg V.,Max Planck Advanced Study Group | Rohringer N.,Max Planck Institute for the Physics of Complex Systems | Rohringer N.,Max Planck Advanced Study Group
Physical Review Letters | Year: 2013

We predict high-gain x-ray lasing in molecular nitrogen by ultrafast core ionization with an x-ray free-electron laser source. To estimate the spectral and temporal output of this molecular x-ray laser, we solve generalized Maxwell-Bloch equations, keeping track of the electronic and nuclear degrees of freedom. The spectrum of the amplified x-ray emission shows a strong dependence on the gain-length product. Whereas the emission at small gain length is similar to the relatively broad x-ray fluorescence band, the spectrum is determined by a single frequency in the linear gain region. The vibrational wave packet dynamics during the x-ray emission process is examined. By preparation of the initial vibrational quantum state, the x-ray emission frequency can be tuned within the fluorescence band. The present scheme is applicable to other homo- and heteronuclear diatomic systems, thereby extending the spectral range of coherent x-ray radiation sources based on amplification on bound transitions. © 2013 American Physical Society.


Gnodtke C.,Max Planck Institute for the Physics of Complex Systems | Saalmann U.,Max Planck Institute for the Physics of Complex Systems | Saalmann U.,Max Planck Advanced Study Group | Rost J.-M.,Max Planck Institute for the Physics of Complex Systems | Rost J.-M.,Max Planck Advanced Study Group
New Journal of Physics | Year: 2011

Intense light with frequencies above typical atomic or molecular ionization potentials as provided by free-electron lasers couples many photons into extended targets such as clusters and biomolecules. This implies, in contrast to traditional multi-photon ionization, multiple single-photon absorption. Thereby many electrons are removed from their bound states and either released or trapped if the target charge has become sufficiently large. We develop a simple model for this photo-activation to study electron migration and interaction. It satisfies scaling relations that help to relate quite different scenarios. Understanding this multi-electron dynamics on very short time scales is vital for assessing the radiation damage inflicted and for paving the way to coherent diffraction imaging of single molecules. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.


Zarrine-Afsar A.,University of Hamburg | Zarrine-Afsar A.,University of Toronto | Barends T.R.M.,Max Planck Institute for Medical Research | Barends T.R.M.,Max Planck Advanced Study Group | And 9 more authors.
Acta Crystallographica Section D: Biological Crystallography | Year: 2012

A new chip-based crystal-mounting approach for rapid room-temperature data collection from numerous crystals is described. This work was motivated by the recent development of X-ray free-electron lasers. These novel sources deliver very intense femtosecond X-ray pulses that promise to yield high-resolution diffraction data of nanocrystals before their destruction by radiation damage. Thus, the concept of diffraction before destruction requires rapid replenishment of the sample for each exposure. The chip promotes the self-assembly of an array of protein crystals on a surface. Rough features on the surface cause the crystals to adopt random orientations, allowing efficient sampling of reciprocal space. © 2012 International Union of Crystallography Printed in Singapore - all rights reserved.


Manschwetus B.,Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy | Rottke H.,Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy | Steinmeyer G.,Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy | Foucar L.,Max Planck Advanced Study Group | And 3 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

We investigate double ionization of argon dimers in high-intensity ultrashort Ti:sapphire laser pulses. We are able to identify several strong-field excitation pathways of the dimer that terminate in atomic ion pairs from a Coulomb explosion. The explosion starts from two-site double-ionized dimers and from one-site double-ionized ones after radiative charge transfer at small internuclear separation. One-site double ionization is accomplished by laser-induced charge transfer in the high-intensity laser pulse following two-site double ionization. The highest energy ion pairs we observed can be attributed to "frustrated triple ionization" of the argon dimer. © 2010 The American Physical Society.


Averbukh V.,Max Planck Institute for the Physics of Complex Systems | Saalmann U.,Max Planck Institute for the Physics of Complex Systems | Saalmann U.,Max Planck Advanced Study Group | Rost J.M.,Max Planck Institute for the Physics of Complex Systems | Rost J.M.,Max Planck Advanced Study Group
Physical Review Letters | Year: 2010

Inner-shell ionization of atoms and molecules leads to the creation of highly excited ionic states that often decay by electron emission. The dynamics of the decay is usually assumed to be exponential and the process is characterized by a decay rate. Here we show that in a multiply ionized cluster created by interaction with a high-intensity free-electron laser (FEL) radiation, trapping of the emitted electron by the neighboring ions changes the character of the decay dynamics qualitatively to the extent that it can become oscillatory instead of exponential. Implications of the predicted effect on Coster-Kronig and interatomic Coulombic decay processes induced by FELs are investigated. © 2010 The American Physical Society.


Krasniqi F.,Max Planck Advanced Study Group | Najjari B.,Max Planck Institute for Nuclear Physics | Struder L.,Max Planck Advanced Study Group | Rolles D.,Max Planck Advanced Study Group | And 3 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

A scheme based on (i) upcoming brilliant x-ray free-electron laser (FEL) sources, (ii) innovative energy and angular-dispersive large-area electron imagers, and (iii) the well-known photoelectron holography is elaborated that provides time-dependent three-dimensional structure determination of small to medium-sized molecules with Ångström spatial and femtosecond time resolution. Inducing molecular dynamics, wave-packet motion, dissociation, passage through conical intersections, or isomerization by a pump pulse this motion is visualized by the x-ray FEL probe pulse launching keV photoelectrons within a few femtoseconds from specific and well-defined sites, deep core levels of individual atoms, inside the molecule. On their way out, the photoelectrons are diffracted generating a hologram on the detector that encodes the molecular structure at the instant of photoionization, thus providing "femtosecond snapshot images of the molecule from within." Detailed calculations in various approximations of increasing sophistication are presented and three-dimensional retrieval of the spatial structure of the molecule with Ångström spatial resolution is demonstrated. Due to the large photoabsorption cross sections the method extends x-ray-diffraction-based time-dependent structure investigations envisioned at FEL's to new classes of samples that are not accessible by any other method. Among them are dilute samples in the gas phase such as aligned, oriented, or conformer-selected molecules, ultracold ensembles and/or molecular or cluster objects containing mainly light atoms that do not scatter x rays efficiently. © 2010 The American Physical Society.


Ullrich J.,Max Planck Institute for Nuclear Physics | Ullrich J.,Max Planck Advanced Study Group | Ullrich J.,Physikalisch - Technische Bundesanstalt | Rudenko A.,Max Planck Institute for Nuclear Physics | And 2 more authors.
Annual Review of Physical Chemistry | Year: 2012

Free-electron lasers are fourth-generation light sources that deliver extremely intense (>10 12 photons per pulse), ultrashort (∼10 -14 s = 10 fs) light pulses at up to kilohertz repetition rates with unprecedented coherence properties and span a broad wavelength regime from soft (∼10 eV) to hard X-ray energies (∼15 keV). They thus enable a whole suite of novel experiments in molecular physics and chemistry: Inspecting radiation-induced reactions in cold molecular ions provides unprecedented insight into the photochemistry of interstellar clouds and upper planetary atmospheres; double core-hole photoelectron spectroscopy offers enhanced sensitivity for chemical analysis; the dynamics of highly excited molecular states, pumped by vacuum ultraviolet pulses, can be inspected; and vacuum ultraviolet or X-ray probe pulses generally hold the promise to trace chemical reactions along an entire reaction coordinate with atomic spatial and temporal resolution. This review intends to provide a first overview on upcoming possibilities, emerging technologies, pioneering results, and future perspectives in this exciting field. © Copyright ©2012 by Annual Reviews. All rights reserved.


Kastner A.,Max Planck Institute for the Physics of Complex Systems | Saalmann U.,Max Planck Institute for the Physics of Complex Systems | Saalmann U.,Max Planck Advanced Study Group | Rost J.M.,Max Planck Institute for the Physics of Complex Systems | Rost J.M.,Max Planck Advanced Study Group
Physical Review Letters | Year: 2012

We introduce soft recollisions in laser-matter interaction. They are characterized by the electron missing the ion upon recollision in contrast with the well-known head-on collisions responsible for high-harmonic generation or above-threshold ionization. We demonstrate analytically that soft recollisions can cause a bunching of photoelectron energies through which a series of low-energy peaks emerges in the electron yield along the laser polarization axis. This peak sequence is universal, it does not depend on the binding potential, and is found below an excess energy of one tenth of the ponderomotive energy. © 2012 American Physical Society.

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