The community of scientists that use soft X-rays from PETRA III (beamline P04) and related sources gathered at DESY to discuss their recent insights as well as new developments and installations that will be made in the near future. US participants could join only by remote connection due to the US government shutdown. (Credit: DESY)
The scientific insights achieved with soft X-rays from the PETRA III were discussed in an international workshop at DESY on 17 and 18 November 2025. The over 80 participants from three continents, discussed results and developments in 26 talks and 25 posters. Soft X-rays are generated and delivered for user experiments at the PETRA III beamline P04. This range of the X-ray spectrum enables detailed studies of the interaction of radiation with matter.
Following a welcome by the DESY Photon Science director, Britta Redlich, the first day saw a broad range of deep insights from photoionization experiments on molecules, including studies of the molecular structure in photodissociation studies. Namely, the use of circular polarization of the X-rays from the beamline P04 led to discoveries about the chiral structure of highly relevant molecules, both in the gas phase and dissolved in water. Atomic ions that are also found in interstellar dust were further studied in laboratory-based experiments, which are crucial for the correct interpretation of space-borne telescopes.
The high degree of coherence of these X-rays is a key enabling factor for studies of magnetic structures and other emergent textures in materials. These structures and their dynamics were discussed in several presentations on the second day. This day was opened by a keynote lecture by Jens Viefhaus of Helmholtz-Zentrum-Berlin (HZB). He presented the vision behind and the works conducted to outfit the synchrotron BESSY II of HZB with the most pressingly needed synchrotron beamlines and bringing research one step further by the planned upgrade BESSY III.
The third major topic of the workshop was the experiments conducted on novel materials that show intriguing quantum phenomena. These materials are intensely studies on beamline P04 by several instruments that use the technique of angle-resolved photoemission spectroscopy. The quantum structures, that include chiral nano-currents and a Berry phase tornado, display their full repertoire of potentially very useful electronic phenomena through their electronic structure that is visualized in the photoemission experiments and further clarified by the use of the additional symmetry of the polarization of the X-rays.
The workshop was conducted by the consortium of scientists interested in the use of soft X-rays. This included both experts in the field as well as students. The discussions during the coffee breaks and at the workshop dinner, as well as the lively exchange about the content of the posters displayed during the workshop, were very useful.
To solve open questions, users will continue to benefit from the soft X-rays at P04 at PETRA III and, in future, also from the planned upgrade to PETRA IV.
