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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.


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.


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.


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.

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