Highlights

From November 4 - 11, 2024, Johannes Viehmann, Yusaku Terao, Simeon Bürger and Niklas Golchert experimented at the FinEstBeAMS beamline of the synchrotron radiation facility MAX IV in Lund, Sweden. Here they installed the EPIC setup (short for electrons and photons in coincidence) to measure multi-electron photon coincidence spectra of pure neon and mixed neon-krypton clusters. One focus was on the suppression of the ICD (short for: Interatomic Coulombic Decay) process by the presence of a neighboring ion within a cluster.

On 05.11.2024 Daniel Hermann successfully defended his bachelor thesis with the title Simulation Based Comparison of Electrode Configurations for Velocity Map Imaging Spectrometers.

We wish you all the best for your future!

From 22 - 29.10.2024 Emilia Heikura, Adrian Krone, Andreas Anschütz, Dana Bloß and Madhusree Roy-Chowdhury, actively supported by Florian Trinter (FHI Berlin), conducted an experiment on the distance dependence of photoelectron circular dichroism, an effect that occurs during the ionization of chiral molecules by circularly polarized light. For this purpose, a molecular jet was crossed with circularly polarized synchrotron radiation, provided by the P04 beamline of the PETRA III storage ring, and the emitted electrons were measured with a VMI spectrometer (short for Velocity Map Imaging).

On the 15th of October 2024, Julian Hertlein successfully defended his Bachelor thesis with the title Vermessung der lateralen Quanteneffizienz eines positionssensitiven Photonendetektors.

We wish you best of luck for your future!

On 10th of September 2024, Volodymyr Zhyrnyi successfully defended his Bachelor thesis with the title Untersuchung von Systemen mit doppeltem Exchange Bias für den Transport magnetisch funktionalisierter Partikel.

We wish you best of luck for your future!

Since August 2024, we are glad to welcome former Master student Nikolai Weidt as PhD student in our group. We wish you best of luck!

From 21.07. - 30.07.2024 Johannes Viehmann, Yusaku Terao and Niklas Golchert, actively supported by Ouassim Hocine Hafiani (Uppsala University, Sweden), experimented at the PLÉIADES beamline of the synchrotron Soleil. They were interested in the fluorescence spectra of noble gas clusters after inner-shell excitation with a special focus on the postulated neighbor induced recapture process, whose photon spectrum has never been investigated before.

On 18.06.2024, Nikolai Weidt successfully gave the defense of his Master thesis with the title Remote-Controlled Transport of Superparamagnetic Particles in Liquid: Simulation and Experimental Analysis of Three-Dimensional Trajectories.

We wish you only the best for your future!

From 16.06. - 25.06.2024, Niklas Golchert, Yusaku Terao, Madhusree Roy-Chowdhury, Emilia Heikura and Andreas Hans experimented at the GALAXIES beamline of the synchrotron Soleil, where they were supported by Minna Patanen (University of Oulu) and Oksana Travnikova (CNRS). During this first-time combination of our setup EPIC (electrons and photons in coincidence) with a hard x-ray beamline, multielectron-photon coincidence spectra of Argon clusters after 1s ionization were measured. The resulting spectra will contain information about the different non-local processes occuring during the relaxation of these excited systems.

From 05.06. - 12.06.2024, Yusaku Terao, Johannes Viehmann, Gabriel Klassen, Christina Zindel und Catmarna Küstner-Wetekam experimented at the P04 beamline of the PETRA III accelerator in Hamburg. They recorded luminescence spectra of solvated nucleotides (Adeninmonophosphate AMP and Uridinemonophosphate UMP). These are supposed to yield information about the deexcitation of DNA components after X-ray irradiation when they are embedded in a watery environment.

On 30.05.2024,  our group published an article in Nature Communications. A radiation damage cycle in X-ray-ionized solvated Mg ions is reported by the authors leading to production of water radicals and low-energy electrons. The Mg ion ends in its initial state quickly and can restart the cycle, multiplying the local damage. 

D. Bloß et al., "X-ray radiation damage cycle of solvated inorganic ions", Nature Communications, 15, 4594 (2024).
DOI: https://doi.org/10.1038/s41467-024-48687-2

Also interesting: Press release of the university of Kassel.

In the period from 19.05. - 04.06.2024, our group absolved two beamtimes at the FlexPES beamline of the MAX IV storage ring in Lund, Sweden. The experiments were performed by Yusaku Terao, Niklas Golchert, Johannes Viehmann, Joel Herrmann, Gabriel Klassen, Emilia Heikura, Dana Bloß, Andreas Hans and Adrian Krone with the helpful support of Noelle Walsh and Maxim Tchaplyguine.

During the first experiment, the fluorescence of solvated nucleotides (Cytidinmonophosphate CMP) was measured, in order to investigate their relaxation after inner-shell ionization by X-rays. For this purpose, a liquid microjet was combined with a Seya-Namioka spectrometer. In the second experiment, a magnetic-bottle-type electron spectrometer was used in combination with a rare-gas cluster source in order investigate multiple (non-local) processes in prototypical many-particle systems with the multielectron coincidence technique.

On 16.05.2024, our group published an article in Physical Review Letters, where the Auger decay of an atom inside of a cluster is discussed, while an elementary charge is present in its close viscinity. This charge influences the measured electron spectra in dense media and needs to be considered for their correct interpretation. 

A. Hans et al., "Experimental realization of Auger decay in the field of a positive elementary charge", Physical Review Letters 132, 20 (2024).
DOI: 10.1103/PhysRevLett.132.203002

From 22. - 29.04.2024, Emilia Heikura, Andreas Hans, Johannes Viehmann, Leon Schwarz and Madhusree Roy-Chowdhury were experimenting at the P04 beamline of the PETRA III storage ring in Hamburg. They were studying photoelectron circular dichroism (PECD) on electrons with high kinetic energy after participator Auger decay in the chiral molecule methyloxirane.

Welcome Joel Herrmann and Leon Schwarz. We wish you a good time in the AG Ehresmann!

From 31.03. - 09.04.2024, Madhusree Roy-Chowdhury, Andreas Hans, Christina Zindel, Emilia Heikura, Johannes Viehmann and Niklas Golchert experimented at the FinEstBeAMS beamline of the MAX IV storage ring in Sweden. They investigated the fragmentation pattern of pyrmidine-water clusters after inner-shell ionization of the water and pyrimidine molecules using the PePiPiCo (Photoelectron-Photoion-Photoion-Coincidence) method. The results are expected to give additional insights in the protective or destructive effects of watery environments to X-ray irradiated biomolecules.

From 17. -22.03.2024, Bhavadip Rakholiya, Christian Janzen, Jonas Bugase, Nikolai Weidt, Rico Huhnstock and Yahya Shubbak participated in the Spring meeting of the German Physical Society (DPG) for the Section condensed matter (SKM) in Berlin. They contributed 3 talks, 3 posters and 1 science slam to the scientific programme of the conference.

From 10. - 15.03.2024, Adrian Krone, Andreas Hans, Arno Ehresmann, Catmarna Küstner-Wetekam, Christina Zindel, Dana Bloß, Emilia Heikura, Johannes Viehmann, Lutz Marder, Madhusree Roy-Chowdhury, Niklas Golchert and Yusaku Terao participated in  the Spring meeting of the German Physical Society DPG for the Section Atoms, Molecules, Quantum Optics and Photonics (SAMOP) in Freiburg. They contributed 10 talks and 1 poster to the scientific programme of the conference.

From 28.02. - 06.03.2024, Niklas Golchert, Adrian Krone, Andreas Anschütz, Andreas Hans, Emilia Heikura and Johannes Viehmann performed an experiment at the P04 beamline of the storage ring PETRA III in Hamburg. They investigated the local and non-local relaxation mechanisms occuring in rare-gas clusters after excitation with X-rays. For this purpose, they combined an electron spectrometer with a mirror system, therefore enabling the coincident detection of multiple electrons and photons.

Welcome Volodymyr Zhyrnyi. We wish you a good time in the AG Ehresmann!

From 11. - 16.02.2024 Dana Bloß, Emilia Heikura, Niklas Golchert and Yusaku Terao participated at the 44. EAS conference in Riezlern, Austria. In more than 50 talks, recent research results regarding light-matter interaction, highly charged ions, structured light and many other topics were presented. In between the scientific program in the morning and evening, the afternoon could be utilized for skiing or hiking in the mountains.

On 17.01.2024, Valerija Music successfully defended her doctoral thesis with the title Towards the investigation of ultrafast dynamics in chiral systems using free-electron lasers. 

We wish you only the best for your future!

Since december 2023, Dr. Madhusree Roy-Chowdhury supports the spectroscopy team as a postdoc. We wish you a successful time in the AG Ehresmann!

From 29.11. - 01.12.2023 Andreas Hans, Dana Bloß and Emilia Heikura represented our group with one talk and two posters at the "Soft X-ray Science at PETRA" workshop on the DESY (Deutsches Elektronen-Synchrotron) campus in Hamburg. 

From 18.11 - 27.11.2023 Yusaku Terao, Dana Bloß, Gabriel Klassen, Johannes Viehmann, Andreas Hans, Adrian Krone and Niklas Golchert performed an experiment at the FlexPES beamline of the storage ring MAX IV in Lund, Sweden. They used a liquid micro-jet to investigate the electron emission spectra of solvated salts and biomolecules. Special focus lied on the multiple relaxation mechanisms that occur after ionization by X-rays.

From 26.10.-03.11.2023, Arne Vereijken, Varun Vanakalapu, Christian Janzen and Rico Huhnstock employed polarized neutron reflectometry at the world's most potent neutron source, the ILL in Grenoble, in order to examine the magnetization of their samples at varying depths and under the influence of an external magnetic field. They intended to confirm the formation of magnetic spiral states induced by two arbitrarily set exchange-bias effects.

Welcome Julian Hertlein and Christopher Wilke. We wish you a good time in the AG Ehresmann!

On 18.10.2023, Sapida Akhundzada successfully defended her doctoral thesis with the title Asymmetric magnetization reversal processes in exchange-biased microstructures. 

We wish you only the best for your future!

In October 2023, Lutz Marder and Niklas Golchert participated at an inhouse beamtime of the Small Quantum Systems (SQS) group of the European X-ray free-electron laser facility (EuXFEL). Goals of the experiment were on one hand the establishment of the "angular streaking" method as a tool for the characterization of attosecond soft X-ray pulses and on the other hand the implementation of intelligent online data analysis by machine learning.

From 01.10-10.10.2023, Emilia Heikura, Christina Zindel, Andreas Hans, Catmarna Küstner-Wetekam, Lutz Marder and Johannes Viehmann conducted an experiment at the synchrotron radiation facility SOLEIL in France. During this experiment, it was investigated how the distance of an atom to the stereocenter of a chiral molecule (here: sec-butyl trimethylsilylether) influences the inner-shell photoelectron circular dichroism (PECD), a common measure for the chirality of molecules.

From the 27.09.-29.09.2023, our yearly group retreat took place. The objective of this event was the discussion of scientific topics in a relaxed environment as well as strengthening the team spirit within the group.