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, 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 5: Jan. - June 2020
Final Operation
Photon energy
0.27 - 3.0 keV
0.27 - 3.0 keV
1% (SASE mode)
monochromator can be used
0.5% (SASE)
0.01 (monochromator)
Pulse duration
25 fs (calculated)
2 - 100 fs
Pulse energy
0.5 - 3 mJ
up to 10 mJ
Number of pulses per train
up to 200
up to 900
Repetition rate
1.1 MHz
4.5 MHz
linear (horizontal)
linear & circular
Focus size
1.5 - 2.5 μm
> 0.5 μm