LDM

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

Generation and measurement of intense few-femtosecond superradiant extreme-ultraviolet free-electron laser pulses

Three-stage superradiant cascade (SRC) starting from an ultraviolet (UV) seed pulse and reaching the EUV spectral range have been realized at FERMI in order to shorten the pulse duration with femtosecond accuracy. N. S. Mirian et al.Nature Photonics 15, 523 (2021)

Enhancement of Above Threshold Ionization in Resonantly Excited Helium Nanodroplets

Clusters and nanodroplets hold the promise of enhancing high-order nonlinear optical effects due to their high local density. Here we explore the nonlinear optical response of He nanodroplets prepared in multiply excited states by irradiation with relatively intense XUV pulses.R.Michiels et al.Physical Review Letters 127 093201 (2021)

Ultrafast Resonant Interatomic Coulombic Decay Induced by Quantum Fluid Dynamics

Here, we directly measure the timescale of interatomic Coulombic decay (ICD) in resonantly excited helium nanodroplets using a high-resolution, tunable, extreme ultraviolet free-electron laser. A.C.LaForge et al. Physical Review X 11, 021011 (2021)

Photoelectric effect with a twist

Photons have fixed spin and unbounded orbital angular momentum (OAM). Here we have found, that the OAM of an optical field can be imprinted coherently onto a propagating electron wave. Our results reveal new aspects of light–matter interaction and point to a new kind of single-photon electron spectroscopy. G. De Ninno et al. Nature Photonics, 14, 554 (2020)

Tracking attosecond electronic coherences using phase-manipulated extreme ultraviolet pulses

The direct control and manipulation of the phase of individual pulses within an XUV pulse sequence opens exciting possibilities for coherent control and multidimensional spectroscopy, but has not been accomplished. Here, we overcome these constraints in a highly time-stabilized and phase-modulated XUV-pump, XUV-probe experiment, which directly probes the evolution and dephasing of an inner subshell electronic coherence. A. Wituschek et al. Nature Communications 11, 883 (2020)

New Method for Measuring Angle-Resolved Phases in Photoemission

Here we present a new attosecond-precision interferometric method of angle-resolved measurement for the phase of the photoionization amplitudes, using two phase-locked extreme ultraviolet pulses of frequency ω and 2ω, from a free-electron laser. D.You et al. Physical Review X, 10, 031070 (2020)

Ultrafast relaxation of photoexcited superfluid He nanodroplets

Superfluid He nanodroplets are ideal model systems for studying the photodynamics in weakly-bound nanostructures, both experimentally and theoretically. The present work shows that it is now possible to follow the relaxation dynamics of free nanodroplets in great detail using ultrashort tunable XUV pulses.
M. Mudrich et al. Nature Communications 11, 112 (2020)

Attosecond pulse shaping using a seeded free-electron laser

We demonstrate amplitude and phase manipulation of the harmonic components of an attosecond pulse train in combination with an approach for its temporal reconstruction. The results presented here open the way to performing attosecond time-resolved experiments with free-electron lasers.
P. K. Maroju et al. Nature 578, 386 (2020)

Illustration: J.Oschwald and C.Callegari.

Tracking the ultraviolet-induced photochemistry of thiophenone during and after ultrafast ring opening

Here we apply time-resolved photoelectron spectroscopy with a seeded extreme ultraviolet free-electron laser to trace the ultrafast ring opening of gas-phase thiophenone molecules following ultraviolet photoexcitation. S. Pathak et al. Nature Chemistry 12, 795 (2020)

Deep neural networks for classifying complex features in diffraction images

This work provides a general introduction on the capabilities of neural networks and provide results on the first domain adaption of neural networks for the use case of diffraction images as input data. J. Zimmermann et al. Physical Review E 99, 063309 (2019)

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News

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.

User Area

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Call for proposals
Click here to check the status of the call for external users (both on FEL-1 and FEL-2).

Last Updated on Thursday, 30 July 2020 11:39