Scientific Instrument SQS

The SQS (Small Quantum Systems) instrument is dedicated to investigations of fundamental processes of light-matter interaction in the soft X-ray wavelength regime. Typical targets are isolated species in the gas phase, such as atoms, molecules, ions, clusters, nanoparticles and large bio-molecules. The main applications focus on processes occurring under irradiation with ultra-short, highly intense X-ray pulses using a variety of spectroscopic techniques.  In particular, studies of non-linear phenomena, such as multiple ionization and multi-photon processes, time-resolved experiments following dynamical processes on the femtosecond timescale, and investigations using coherent scattering techniques are targeted.

The experiments are performed using a state-of-the art experimental platform, taking advantage of the ultrashort pulses, the extreme brilliance, and the high coherence of the soft X-ray pulses at the European XFEL. A powerful and tunable optical laser system is available for time-resolved studies. The SQS instrument provides three experimental stations to the scientific community:

AQS (Atomic-like Quantum Systems), dedicated to experiments on atoms and small molecules,

NQS (Nano-size Quantum Systems), dedicated to investigation on larger systems, such as clusters and nano-particles,

REMI (REaction MIcroscope), enabling the complete characterization of the ionization and fragmentation process for small systems.

A wide range of experimental techniques for spectroscopic investigations using electrons, ions and photons is available, as well as various set-ups for introducing the target sample. The design of the spectrometers has been optimized to take advantage of the high repetition rate, and to enable various types of coincidence methods. The use of soft X-ray photons enables controlled excitations of specific electronic subshells in atomic and site- or element specific excitation in molecular targets.

If you consider submitting a proposal for run 6 (deadline December 11th 2019 16:00 CET), please contact Michael Meyer well in advance. More details on the parameters can be found in the table below and under Instrument.

Photon Beam Parameter
run 6: July - November 2020
Final Operation
Photon energy
0.5 - 3.0 keV, fully tunable
0.27 - 3.0 keV
linear (horizontal)
linear & circular
Pulse energy
up to 5 mJ
up to 10 mJ
Focus size
1 - 3 μm, tunable
> 0.5 μm
Pulse duration
25 fs (calculated)
2 - 100 fs
~1% in SASE mode
monochromator can be used
0.5% (SASE)
0.01 (monochromator)
Number of pulses per train
variable, for example:
400 at 2.2 MHz
200 at 1.1 MHz
100 at 0.5 MHz
10 at 0.1 MHz
up to 900 at 4.5 MHz