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

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)

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)

Complete Characterization of Phase and Amplitude of Bichromatic Extreme Ultraviolet Light

Here we demonstrate a method of determining the absolute phase between two wavelengths in a bichromatic XUV beam, as well as the coherent fraction of the relative intensity. The determination of phase is independent of the intensity of the two wavelengths. M. Di Fraia et al. Physical Review Letters 123, 213904 (2019)

Coherent control schemes for the photoionization of neon and helium in the Extreme Ultraviolet spectral region

This work presents a detailed description of how a seeded Free-Electron Laser can be used to perform some coherent-control experiments using the fundamental and second and third harmonics. The flexible design of FERMI provides excellent control of the wavelength, phase, and amplitude of light emitted by the FEL. L.Giannessi et al. Scientific Reports 8, 7774 (2018)

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)

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 H₂molecule 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 121, 103002 (2018)

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 15, 170 (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.

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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