News Archive

On the 8th of September 2023, the summer barbecue of the Physical Chemistry working groups took place at the Oberförsterwiese nearby the TU Darmstadt Lichtwiese site. In addition to the current staff members, many alumni also attended.

The Schäfer group was represented at the “21st International Symposium on Small Particles and Inorganic Clusters (ISSPIC XXI)”, which took place in Berlin from 3rd to 8th of September 2023.

On July 17, 2023 Andreas Lehr successfully defended his doctoral thesis with the title “The Interplay of Geometric and Electronic Structure in (Doped) Tetrel Clusters: A Study of Optical Spectroscopy and Magnetic Deflection in the Molecular Beam”. Congratulations!

On 30 June 2023, Thomas Fuchs was awarded the Kurt-Ruths Doctoral Prize for his exceptional scientific achievement. Congratulations! The doctoral thesis is entitled “Spin Dynamics of Doped Tin Clusters in the Molecular Beam”.

AK Schäfer was represented at this year's “Cluster Meeting 2023” in the field of cluster catalysis and related areas. The conference took place in Prague from June 18 to 23, 2023.

The AK Schäfer was represented at this year's Bunsen Conference on the topic “Physical Energy of the Energy Transition”. This was organized by the German Bunsen Society in the period 05.06-07.06 at the bcc Berlin Congress Center.

In early 2023, the VUV spectroscopy and UV-Vis spectroscopy experiments were combined. The existing molecular beam apparatus and the associated laser systems were dismantled and combined into one apparatus. At the new apparatus it is thus possible to generate clusters in a molecular beam and subsequently ionize them using the VUV laser system or perform photodissociation experiments using the UV-Vis laser system. Thus, both the ionization potentials and the optical properties of the clusters can be studied in a combined experiment.

A Magnetic Molecular Beam Deflection Study Coupled with Modern Quantum Chemistry

Molecular Magnetism is a thriving field of research with remarkable discoveries being made with single-molecule magnets where d- and f-block elements serve as paramagnetic centers. Tetrel clusters p-doped with elements of the triel group also state magnetically highly relevant systems. If lead is chosen as tetrel cage element, the endohedral clusters are found to exhibit peculiar spin-orbit coupling effects with strongly impacted electronic g-factors.

Our publications in recent months are about a correlated study of the Zeeman and Stark effect on the p-doped tin clusters MSn 12 with M=Al, Ga, In, as well as the observation of linearly scaling dipole moments of quasispherical Si clusters in electric deflection experiments, both supported by modern quantum chemistry.

On December 12, 2022 Julian Baranyai successfully defended his doctoral thesis with the title “Cluster Catalysis Under Technical Conditions: Design of a High-Pressure Cell to Study Coinage Metal Clusters as Heterogeneous Catalysts”. Congratulations!

Since December 2022, Timo Schwab is a PhD student in the Schäfer group. As part of his PhD, he continues the study clusters by means of photodissociation action spectroscopy in the UV-vis spectral range. In the long term, an extension of the experiment by an electric deflection unit for isomer-selective spectroscopy on small neutral clusters is planned.

Roman Kornievskii successfully completes his bachelor thesis in the Schäfer group on 28rd of November, 2022. Congratulations! The thesis is entitled “Investigation of the Electric Deflection of Cold p-Doped Pb 12 M Clusters (M=Al, Ga, In)” and was written in the research field of electric deflection.

A new laser system for the VUV spectroscopy has been installed. With this light source it is possible to determine the ionization potentials of clusters more precisely. In addition, the intensity of the light is much more intense than with the previously used monochromator setup, allowing more cluster species to be measured.

This year's conference of the SFB 1487 “Iron, upgraded!”, which started in January 2022, took place in Weinheim at the Bergstraße. Here, the six universities/institutes came together to present and discuss research progress and prospects, but also future collaborations.

The Schäfer group was attending this year's “Clustertreffen 2022” conference in the field of cluster physics and related areas, held October 2-7, 2022, at the Herzogenhorn in the Black Forest.

From September 21 to 23, 2022, the Faraday Discussion was held in London on the topic “Nanoalloys: Recent Developments and Future Perspectives”, where Prof. Dr. Rolf Schäfer gave a presentation on the topic “Magnetic and Optical Properties of Nanoalloys”.

The Schäfer group was attending this year's conference on “Dynamics of Electrons in Atomic and Molecular Nanoclusters” held by the International School of Solid State Physics of the Ettore Majorana Foundation and the Centre for Scientific Culture in Erice (Sicily), August 25-31, 2022.

Timo Schwab successfully completes his master thesis in the Schäfer working group on 3rd of June, 2022. Congratulations! The thesis is entitled “Design of a Laser Ablation Source for the Production of Small Neutral Clusters and the Integration of a Reactive Gas into the Cluster Formation Process” and was written in the research field of VUV Spectroscopy.

On May 20, 2022, Thomas Fuchs was awarded the PhD prize of the Freunde der TU Darmstadt for his outstanding scientific achievement. Congratulations! The PhD thesis is entitled “Electron Spin Dynamics of Doped Tin Clusters in the Molecular Beam”.

On May 6, 2022, Marc Jäger received the Wolfgang-Paul-Studienpreis of the German Society for Mass Spectrometry for his outstanding scientific dissertation. Congratulations! The PhD thesis is entitled “Optoelectronic properties of molecular semiconductor systems”.

Our publications in recent months are about a long-term study of neutral tin clusters, whose geometrical and optical properties have been investigated by means of electrical deflection and photodissociation spectroscopy experiments in the molecular beam, with the aid of elaborate quantum chemistry. In addition, the construction and testing of a high-pressure cell to study catalytic reactions of surface-deposited nanoclusters was written up.

Since May 2022, David Büchner is a PhD student in the Schäfer group. The aim of his PhD is the further development of the TPD experiment for the analysis of the kinetics of desorption processes as well as oxide reactions on mass-selected, supported metal clusters.

Since January 2022, the Deutsche Forschungsgemeinschaft (DFG) is funding a new Collaborative Research Center at the Technical University of Darmstadt, in collaboration with five other universities/institutes. The Schäfer group participates in this collaborative research center with the project “C07: Influence of Tetrel Atoms as Ligands”.

David Büchner successfully completes his master thesis in the Schäfer working group on 3rd of March, 2022. Congratulations! The thesis is entitled “Temperature Programmed Desorption Study on Monodisperse Deposited Platinumclusters” and was written in the research field of Cluster Catalysis.

On November 1, 2021 Thomas Fuchs successfully defended his doctoral thesis with the title “Electron Spin Dynamics of Doped Tin Clusters in the Molecular Beam”. Congratulations!

Our publications in the last months are related to p-doped tin clusters studied in electric and magnetic deflection experiments. First, the spin dynamics of the Sn12Al cluster was studied in double deflection experiments (magnet-magnet), where it was observed that an increase in the number of nuclear spins leads to increased spin flips. In another work with Sn12Al, two fractions were observed in the electric deflection experiment, which were also studied isomer-selectively in double deflection experiments (electrode-magnet), showing that two isomers are simultaneously present in the molecular beam. In the third work, the focus was on determining the vibrational, rotational, and translational temperatures of SnNGa clusters, thus extending our general understanding regarding cluster formation and cooling in our apparatus.

Chiara Schleif successfully completes her bachelor thesis in the Schäfer working group on 8 July 2021. Congratulations! The thesis is entitled “Laser-Spectroscopic Investigation of Charged and Neutral Tin Clusters in the Molecular Beam” and was written in the research field of UV-Vis Spectroscopy.

As part of this year's digital working group presentation, we have put together a video that will give you a closer look at the workflow in the Schäfer group. In addition, you can get an insight into our laboratory and our way of working.

Our publications in recent months include an experimental-quantum chemical combined study of small cationic CdSe nanoclusters, where besides structure elucidation also the optical behaviour by photoabsorption was investigated. Larger species of these nanoclusters (<27 atoms) were illuminated in a purely theoretical work, which mainly highlights differences to the optical behaviour of colloidal CdSe quantum dots. To elucidate catalytic properties of clusters on surfaces, a radiation heater for high-temperature ultra-high vacuum synthesis was constructed and designed using finite element simulations for the preparation of defined surfaces.

Niklas Wolf successfully completes his bachelor thesis in the Schäfer working group on 25 February 2021. Congratulations! The thesis is entitled “Vacuum Photoion Yield Spectroscopy of Small Tin Clusters: A Theoretical and Experimental Examination” and was written in the research field of VUV Spectroscopy.

On January 25, 2021 Marc Jäger successfully defended his doctoral thesis with the title “Optoelectronic Properties of Molecular Semiconductor Systems”. Congratulations!

Daniel Dyck successfully completes his bachelor thesis in the Schäfer working group on 18 December 2020. Congratulations! The thesis is entitled “Determination of Ionization Potentials of Small Sn N Clusters (N=6-12,15,16)” and was written in the research field of VUV Spectroscopy.

Our publications of the last months include a study on coordination numbers in gadolinium-doped tin clusters. Unusually high coordination numbers of up to 19 were observed. In addition, an apparatus for magnetic resonance experiments on particles in a molecular beam was described and validated on an atomic europium beam. Finally, quantum dynamics studies beyond the Born-Oppenheimer approximation were performed on a small heterocycle in order to be able to interpret vibrationally-resolved absorption spectra of clusters in the context of vibronic coupling in the future.

Niklas von Rhein successfully completed his bachelor thesis in the Schäfer group on September 10, 2020. Congratulations! The thesis is entitled “Adsorption Studies of Small Lewis Bases on Metal and Oxide Surfaces Using Density Functional Theory” and was prepared in the field of cluster catalysis.

An Investigation of the Optical Properties of Sn₁₄

The cluster research of isolated particles in the molecular beam differs fundamentally from the preparation and characterization of mostly ligand-stabilized nanoparticles in colloidal solutions. While the former is particularly suitable for elucidating fundamental properties and thus belongs to classical basic research, the synthesis of clusters in solution is a direct way to explore potential applications in e.g. catalysis. It is therefore of central interest to clarify the extent to which results from the gas phase can be transferred to cluster systems in solution. In this context, we have for the first time investigated isolated clusters, here Sn₁₄, in a molecular beam with respect to their optical behavior and compared them with a ligand-stabilized analogue in a benzene solution.

On June 29, 2020 Martin Gleditzsch successfully defended his doctoral thesis with the title “Doping of Nanoscale Tin Clusters: Molecular Beam Experiments and Density Functional Theory”. Congratulations!

David Schlander successfully completed his bachelor thesis in the Schäfer group on June 19, 2020. Congratulations! The thesis is entitled “Construction and Testing of a Radiant Heating System for the Preparation of Pure and Oxidic Silicon Surfaces in Ultra-High Vacuum” and was prepared in the field of cluster catalysis.

Due to the TUDa's guidelines on digital teaching, we will also make our lectures available online at Moodle. On Thursdays both lectures will be available for one week. The exercises can either be obtained directly from Moodle or as usual from our website. The exercises are released on Mondays with the sample solution of the previous week.

On April 6, 2020 Oxana Sander successfully defended her doctoral thesis with the title “Construction and Testing of an Ion Beam Apparatus for the Determination of Bond Dissociation Energies”. Congratulations!

On November 27, 2019 Prof. Dr. Rolf Schäfer received the Athens Prize for good teaching, especially for extremely well-structured classical blackboard lectures.

In November 2019 Alexander Macion and Filip Rivic started working as doctoral students in the Schäfer group. Alexander Macion is working on the setup of an experiment for VUV spectroscopy to measure redox and ionization potentials. Filip Rivic expands and continues research on the electrical deflection of clusters in the molecular beam.