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Low Density Matter at FERMI

The Low Density Matter (LDM) beamline has been built as part of the FERMI free-electron laser (FEL) facility to serve the atomic, molecular and cluster physics community.

The LDM beamline features a modular end-station accommodating a broad range of detectors and systems for producing targets. The combined capabilities of the photon source (high brilliance, short pulse length, variable polarization, coherence), photon transport (variable-focusing optics) and end-station allow the investigation of many targets, such as very dilute systems, matter under extreme irradiation conditions (multiple electronic excitation, multiple ionization, Coulomb explosion, non-linear optics) and dichroism. The split-and-delay line as well as, a synchronized optical laser allows time-resolved experiments with different combinations of femtosecond pulses.

The beamline was commissioned in 2012 and is undergoing rapid development. The LDM beamline is now open to external users .

Research highlights | Publications

Symmetry breakdown of electron emission in extreme ultraviolet photoionization of argon

The existence of unexpectedly strong asymmetric emission patterns of electrons from sequentially ionized argon atoms in the vicinity of the respective Cooper minimum has been experimentally demonstrated by using intense femtosecond XUV pulses from the FEL-1 of FERMI. M. Ilchen et al. Nature Communications, Vol. 9, pp. 4659 (2018). 

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Acetylacetone photodynamics at a seeded free-electron laser

The unique combination of high intensity and energy resolution of the FERMI seeded free-electron laser (FEL) provided exceptionally detailed information about the photoexcitation-deexcitation and fragmentation dynamics of acetylacetone in pump-probe experiments on the 50-femtosecond time scale. R.J.Squibb et al. Nature Communications 9, 63 (2018)

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Control of H2 Dissociative Ionization in the Nonlinear Regime Using Vacuum Ultraviolet Free-Electron Laser Pulses

An important step towards the understanding and control of photoinduced fragmentation processes in molecules has been achieved in an experiment on the Hmolecule taking advantage of the unique properties of the FERMI free-electron laser source in the vacuum ultraviolet (VUV) photon energy range. F. Holzmeier  et al. Physical Review Letters, Vol. 121 - 10, pp. 103002 (2018)

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Complete reconstruction of bound and unbound electronic wavefunctions in two-photon double ionization

By controlling the polarization of the VUV–XUV light from the FERMI, the bound and continuum components of the system in the first and second ionization steps leading to the formation of doubly charged neon ions have been determined. P. Carpeggiani et al. Nature Physics. Vol. 15, pp. 170-177 (2019)

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Three-Dimensional Shapes of Spinning Helium Nanodroplets

The single-shot diffraction patterns of individual rotating helium nanodroplets up to large scattering angles have been measured by using intense extreme ultraviolet light pulses from the FERMI free-electron laser. B.Langbehn et al. Physical Review Letters, Vol. 121 - 25, pp. 255301 (2018)

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Impulsive laser-induced alignment of OCS molecules at FERMI

We have demonstrated laser induced alignment of OCS molecules in the impulsive regime. Revival dynamics were observed for ionic fragments produced after ionization and Coulomb explosion in aligned molecules.  M. Di Fraia et al. Physical Chemistry Chemical Physics (2017)

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Slow Interatomic Coulombic Decay of Multiply Excited Neon Clusters

Ne clusters (∼5000  atoms) were resonantly excited (2p→3s) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited clusters can decay nonradiatively via energy exchange between at least two neighboring excited atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites of the Ne clusters were probed. D. Iablonskyi et al. Physical Review Letters, Vol. 117 - 27, pp. 276806 (2016)

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Coherent control with a short-wavelength free-electron laser

Here, we demonstrate the phase correlation of two colours, and manipulate it to control an experiment. Light of wavelengths 63.0 and 31.5 nm ionized neon, and we controlled the asymmetry of the photoelectron angular distribution by adjusting the phase, with a temporal resolution of 3 as. K. C. Prince et al. Nature Photonics, Vol. 10 - N, pp. 176-179 (2016)


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Time-resolved measurement of interatomic Coulombic decay induced by two-photon double excitation of Ne2

The hitherto unexplored two-photon doubly excited states [Ne*(2p−13s)]2 were experimentally identified using the seeded, fully coherent, intense extreme ultraviolet free-electron laser FERMI. These states undergo ultrafast interatomic Coulombic decay (ICD), which predominantly produces singly ionized dimers.  T. Takanashi et al. Physical Review Letters, Vol. 118 - 3, pp. 033202 (2017)

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Circular Dichroism in Multiphoton Ionization of Resonantly Excited He Ion

Intense, circularly polarized extreme-ultraviolet and near-infrared (NIR) laser pulses are combined to double ionize atomic helium via the oriented intermediate He+(3p) resonance state. Applying angle-resolved electron spectroscopy, we find a large photon helicity dependence of the spectrum and the angular distribution of the electrons ejected from the resonance by NIR multiphoton absorption. M.Ilchen et al.  Physical Review Letters, Vol. 118 - 1, pp. 013002 (2017)

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  New VMI + TOF setup for LDM

  An upgrade of the VMI spectrometer has been designed and built up recently at LDM.
  Advantages of the new setup:
  •Less sensitive to the misalignment,
  •Less sensitive to the stray light,
  •Improved ion-TOF collection efficiency.

 Scattering detector commissioning at LDM


  The LDM scattering detector has been recently commissioned. The image shows the single-cluster scattering pattern from a He droplet of diameter 950 nm, taken with FERMI pulses at a wavelength of 64 nm.


Magnetic bottle commissioning at LDM

A magnetic bottle spectrometer, designed and built by Raimund Feifel and co-workers, has been installed, commissioned, and used for beamtime at LDM. The image shows a test spectrum, with O2 as target gas, taken at 21.2 eV photon energy
[contact: http://www.physics.gu.se/english/about-the-department/staff?languageId=100001&userId=xfeira ]

 VMI station at LDM

  An experimental station, devoted to experiments on gaseous samples at the Elettra GasPhase beamline and at LDM, was built and commissioned. The station is based on a Velocity Map Imaging detector for angular resolved photoelectron spectroscopy. A thorough description of this photoelectron analyser has been recently published in Nucl. Instr. Meth. B (2011),  doi:10.1016/j.nimb.2011.07.020. 




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Last Updated on Wednesday, 14 November 2018 14:34