15 research outputs found
Two-photon double ionization of neon using an intense attosecond pulse train
We present the first demonstration of two-photon double ionization of neon
using an intense extreme ultraviolet (XUV) attosecond pulse train (APT) in a
photon energy regime where both direct and sequential mechanisms are allowed.
For an APT generated through high-order harmonic generation (HHG) in argon we
achieve a total pulse energy close to 1 J, a central energy of 35 eV and a
total bandwidth of eV. The APT is focused by broadband optics in a
neon gas target to an intensity of Wcm. By tuning
the photon energy across the threshold for the sequential process the double
ionization signal can be turned on and off, indicating that the two-photon
double ionization predominantly occurs through a sequential process. The
demonstrated performance opens up possibilities for future XUV-XUV pump-probe
experiments with attosecond temporal resolution in a photon energy range where
it is possible to unravel the dynamics behind direct vs. sequential double
ionization and the associated electron correlation effects
High-resolution macromolecular crystallography at the FemtoMAX beamline with time-over-threshold photon detection
Protein dynamics contribute to protein function on different time scales. Ultrafast X-ray diffraction snapshots can visualize the location and amplitude of atom displacements after perturbation. Since amplitudes of ultrafast motions are small, high-quality X-ray diffraction data is necessary for detection. Diffraction from bovine trypsin crystals using single femtosecond X-ray pulses was recorded at FemtoMAX, which is a versatile beamline of the MAX IV synchrotron. The time-over-threshold detection made it possible that single photons are distinguishable even under short-pulse low-repetition-rate conditions. The diffraction data quality from FemtoMAX beamline enables atomic resolution investigation of protein structures. This evaluation is based on the shape of the Wilson plot, cumulative intensity distribution compared with theoretical distribution, I/σ, Rmerge /Rmeas and CC1/2 statistics versus resolution. The FemtoMAX beamline provides an interesting alternative to X-ray free-electron lasers when studying reversible processes in protein crystals
Photodissociation dynamics of the diamondoid adamantane induced by attosecond XUV pulses
International audienceSynopsis Adamantane is the simplest of the diamondoid molecules, which due to their high stability are of high interest both in astrophysics and nanotechnology. This work investigates the molecular photodissociation after ionization by attosecond XUV pulses. The fragmentation dynamics is inferred by means of velocity map imaging spectrometry, covariance analysis techniques and quantum chemistry calculations
Two-photon double ionization of neon studied with intense attosecond pulse trains
We focused an intense attosecond pulse train into a neon gas target and observed Ne2+ resulting from two-photon double ionization. By modifying the photon spectrum we find that the process is dominated by the sequential ionization via the Ne+ ion
Energy scaling of gas nonlinear optics
Nonlinear light-matter interactions, such as filamentation or high-order harmonic generation, are at the heart of nonlinear optics. Scaling of such effects is crucial to benefit optimally from novel laser developments. We introduce and discuss a general scaling model for nonlinear light-matter interactions in gases
High-average power high-harmonic and attosecond sources : Status and prospects
Experiments employing extreme ultraviolet sources based on high harmonic generation often suffer from photon flux limitations. We discuss current status and prospects for scaling such sources to higher repetition rate, pulse energy and average power