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. 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 regular proposal for run 9 (deadline June 22 2022, 4 pm CEST), please contact a member of the instrument team well in advance. All experimental stations, AQS, NQS, and REMI are available. Offered X-ray parameters are listed below. Further information:

Photon Beam Parameter
run 9: January - July 2023
Photon energy
0.5 - 3.0 keV, fully tunable
Pulse energy
up to 10 mJ (depends on photon energy)
Focus size
1 - 3 μm, tunable
Pulse duration
10-25 fs (in normal operation)
~1% in SASE mode or
monochromatized (resolution: 5000 in 1st order)
Number of pulses per train
variable, for example:
400 at 2.2 MHz
200 at 1.1 MHz
100 at 0.5 MHz
20 at 0.1 MHz
Special mode*: two-color operation
Includes a variable time delay between 0 and 1000 fs using a magnetic chicane. (The optical chicane for scanning to negative delays is not yet available.)
Special mode*: short pulses (<10 fs)
Short pulses can be achieved either by special tapering of the undulators or by reducing the electron bunch charge. The latter requires a sufficient number of experiments at several instruments. Time-diagnostics are only partially available.

* Please enquire with the instrument team for details on these modes. Expect significantly reduced pulse energies, more tuning time and less stable operation. Proposals should focus on the development of new techniques facilitated by these modes.