Max Planck Advanced Study Group at CFEL

Hamburg, Germany

Max Planck Advanced Study Group at CFEL

Hamburg, Germany
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Schnorr K.,Max Planck Institute for Nuclear Physics | Senftleben A.,Max Planck Institute for Nuclear Physics | Kurka M.,Max Planck Institute for Nuclear Physics | Rudenko A.,Max Planck Advanced Study Group at CFEL | And 29 more authors.
Physical Review Letters | Year: 2013

The lifetime of interatomic Coulombic decay (ICD) [L. S. Cederbaum et al., Phys. Rev. Lett. 79, 4778 (1997)] in Ne2 is determined via an extreme ultraviolet pump-probe experiment at the Free-Electron Laser in Hamburg. The pump pulse creates a 2s inner-shell vacancy in one of the two Ne atoms, whereupon the ionized dimer undergoes ICD resulting in a repulsive Ne +(2p-1)-Ne+(2p-1) state, which is probed with a second pulse, removing a further electron. The yield of coincident Ne+-Ne2+ pairs is recorded as a function of the pump-probe delay, allowing us to deduce the ICD lifetime of the Ne2+(2s -1) state to be (150±50) fs, in agreement with quantum calculations. © 2013 American Physical Society.


Fukuzawa H.,Tohoku University | Fukuzawa H.,RIKEN | Son S.-K.,German Electron Synchrotron | Motomura K.,Tohoku University | And 31 more authors.
Physical Review Letters | Year: 2013

We have investigated multiphoton multiple ionization dynamics of xenon atoms using a new x-ray free-electron laser facility, SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan, and identified that Xen+ with n up to 26 is produced at a photon energy of 5.5 keV. The observed high charge states (n≥24) are produced via five-photon absorption, evidencing the occurrence of multiphoton absorption involving deep inner shells. A newly developed theoretical model, which shows good agreement with the experiment, elucidates the complex pathways of sequential electronic decay cascades accessible in heavy atoms. The present study of heavy-atom ionization dynamics in high-intensity hard-x-ray pulses makes a step forward towards molecular structure determination with x-ray free-electron lasers. © 2013 American Physical Society.


Jiang Y.H.,Max Planck Institute for Nuclear Physics | Pfeifer T.,Max Planck Institute for Nuclear Physics | Rudenko A.,Max Planck Advanced Study Group at CFEL | Herrwerth O.,Max Planck Institute of Quantum Optics | And 13 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

Using a split-mirror stage combined with a reaction microscope, nonlinear autocorrelation traces of XUV pulses from the Free-electron LASer at Hamburg were recorded for N2 multiphoton-induced fragmentation into noncoincident N2⊃+ and coincident N2⊃++N2⊃+ channels. We find a pulse duration of 40±10 fs along with a sharp spike pointing to a coherence time of 4±1 fs, almost twice as short as in previous observations. Both are well reproduced by a simulation based on the partial-coherence model that includes the molecular dynamics leading to an ~12-fs substructure in the trace. © 2010 The American Physical Society.


Schorb S.,SLAC | Gorkhover T.,TU Berlin | Cryan J.P.,SLAC | Glownia J.M.,SLAC | And 20 more authors.
Applied Physics Letters | Year: 2012

X-ray-optical pump-probe experiments at the Linac Coherent Light Source (LCLS) have so far been limited to a time resolution of 280 fs fwhm due to timing jitter between the accelerator-based free-electron laser (FEL) and optical lasers. We have implemented a single-shot cross-correlator for femtosecond x-ray and infrared pulses. A reference experiment relying only on the pulse arrival time information from the cross-correlator shows a time resolution better than 50 fs fwhm (22 fs rms) and also yields a direct measurement of the maximal x-ray pulse length. The improved time resolution enables ultrafast pump-probe experiments with x-ray pulses from LCLS and other FEL sources. © 2012 American Institute of Physics.


Camus N.,Max Planck Institute for Nuclear Physics | Fischer B.,Max Planck Institute for Nuclear Physics | Kremer M.,Max Planck Institute for Nuclear Physics | Sharma V.,Max Planck Institute for Nuclear Physics | And 11 more authors.
Physical Review Letters | Year: 2012

The strong-field induced decay of a doubly excited, transient Coulomb complex Ar **→Ar2 ++2e - is explored by tracing correlated two-electron emission in nonsequential double ionization of Ar as a function of the carrier-envelope phase. Using <6fs pulses, electron emission is essentially confined to one optical cycle. Classical model calculations support that the intermediate Coulomb complex has lost memory of its formation dynamics and allows for a consistent, though model-dependent definition of "emission time," empowering us to trace transition-state two-electron decay dynamics with sub-fs resolution. We find a most likely emission time difference of ∼200±100 as. © 2012 American Physical Society.


Rajkovic I.,Max Planck Institute for Biophysical Chemistry | Busse G.,Max Planck Institute for Biophysical Chemistry | Hallmann J.,Max Planck Institute for Biophysical Chemistry | More R.,Max Planck Institute for Biophysical Chemistry | And 11 more authors.
Physical Review Letters | Year: 2010

In this Letter, we report the pioneering use of free electron laser radiation for the investigation of periodic crystalline structures. The diffraction properties of silver behenate single nanocrystals (5.8 nm periodicity) with the dimensions of 20nm×20nm×20μm and as powder with grain sizes smaller than 200 nm were investigated with 8 nm free electron laser radiation in single-shot modus with 30 fs long free electron laser pulses. This work emphasizes the possibility of using soft x-ray free electron laser radiation for these crystallographic studies on a nanometer scale. © 2010 The American Physical Society.


Singh K.P.,Indian Institute of Science | Rost J.M.,Max Planck Institute for the Physics of Complex Systems | Rost J.M.,Max Planck Advanced Study Group at CFEL
Chemical Physics | Year: 2010

We investigate dynamics of atomic and molecular systems exposed to intense, shaped random fields and a weak femtosecond laser pulse theoretically. As a prototype example, the photoionization of a hydrogen atom is considered in detail. The net photoionization undergoes an optimal enhancement when a broadband random field is added to the weak laser pulse. The enhanced ionization is analyzed using time-resolved wavepacket evolution and the population dynamics of the atomic levels. We elucidate the enhancement produced by spectrally shaped random fields of two different classes, one with a tunable bandwidth and another with a narrow bandwidth centered at the first atomic transition. Motivated by the large bandwidth provided in the high harmonic generation, we also demonstrate the enhancement effect exploiting random fields synthesized from discrete, phase randomized, odd-order and all-order high harmonics of the driving pulse. These findings are generic and can have applications to other atomic and simple molecular systems. © 2010 Elsevier B.V. All rights reserved.


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 at CFEL | Rost J.-M.,Max Planck Institute for the Physics of Complex Systems | Rost J.-M.,Max Planck Advanced Study Group at CFEL
Chemical Physics | Year: 2013

The photo-electron spectrum resulting from multi-photon absorption of an extended target, such as an atomic cluster or a large molecule, from an intense laser pulse with photon energies larger than the ionization potential of the atomic constituents is discussed. We develop an approximate analytical framework and provide simple analytical expressions for the shape of the photo-electron spectrum in the limit of sequential and parallel ionization, realized by long and short pulses, respectively. The width of the spectrum provides valuable information about the absorbed photons of the target in relation to its extension. © 2012 Elsevier B.V. All rights reserved.


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 at CFEL | Rost J.-M.,Max Planck Institute for the Physics of Complex Systems | Rost J.-M.,Max Planck Advanced Study Group at CFEL
Physical Review Letters | Year: 2012

Massively parallel ionization of many atoms in a cluster or biomolecule is identified as a new phenomenon of light-matter interaction which becomes feasible through short and intense FEL pulses. Almost simultaneously emitted from the illuminated target the photo-electrons can have such a high density that they interact substantially even after photoionization. This interaction results in a characteristic electron spectrum which can be interpreted as a convolution of a mean-field electron dynamics and binary electron-electron collisions. We demonstrate that this universal spectrum can be obtained analytically by summing synthetic two-body Coulomb collision events. Moreover, we propose an experiment with hydrogen clusters to observe massively parallel ionization. © 2012 American Physical Society.


Averbukh V.,Max Planck Institute for the Physics of Complex Systems | Averbukh V.,Imperial College London | Saalmann U.,Max Planck Institute for the Physics of Complex Systems | Saalmann U.,Max Planck Advanced Study Group at CFEL | And 2 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

We consider the Auger decay of atomic inner-shell vacancies in the field of a positive charge, as it occurs in multiply ionized molecules and clusters in strong x-ray laser pulses. First-principles numerical calculations of the decay rate as a function of the ion-charge distance are presented for a series of Auger transitions. The dependence of the rate on the distance is analyzed qualitatively within the Wentzel theory. Our results show that Auger rates can be modified significantly at ion-charge distances of the order of chemical bond lengths. The origin of the predicted effect is traced back to the distortion of the valence orbitals by the field of the positive charge. © 2012 American Physical Society.

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