Open positions

Inviting applications for two doctoral student positions

Research Training Group GRK 2717 DynCAM

Ion mobility mass spectrometry or electronic state chromatography, combined with gas-discharge ion sources, is an ideal tool to select ions of 3d transition elements in ground or excited electronic states that are not necessarily linked by dipole-allowed or one-electron transitions. Here, ion mobility mass spectrometry and cryogenic ion trapping with our ion trap endstation at BESSY II will be employed to prepare cold and electronic state-selected ions of 3d transition elements for x-ray spectroscopy.

Ionization of transition elements in a gas discharge produces ground and excited state electronic configurations that are separated by the mobility analyser. A cryogenic ion trap will be used to accumulate and cool the ions, and serves as the interaction region with X-ray photons. For a given element, ground states, as well as long-lived excited states that differ in 3d electron configuration, will be of particular interest for high-resolution X-ray absorption and X-ray linear dichroism spectra in order to fundamentally test XMCD sum rules, and will give a library of experimental XAS and XMCD data that are important for computational developments in high-level theory for X-ray absorption spectroscopy. Changes in transition metal L-edge excitation energy with 3d electron configuration will also contribute to a fundamental understanding of the empiric concept of oxidation states. First steps towards state or isomer-selective X-ray spectroscopy of larger ions will be made.

The work program will consist of an initial phase of laboratory work to prepare transitions metal ions in well-defined electronic states, followed by campaigns at the BESSY II synchrotron radiation facility for X-ray absorption and XMCD spectroscopy.

See GRK 2717, Dynamics of Controlled Atomic and Molecular Systems (DynCAM) for more information.

Helmholtz-Zentrum Berlin and Max-Planck-Institut Mülheim

We are looking for a PhD student to work on fundamental aspects in energetics and structure of molecular complexes and clusters with wavefunction-based computational protocols (ORCA) and state-of-the-art XAS and XMCD spectroscopy.

The objective is to probe, with wavefunction-based methods, the transition from coordinatively unsaturated to coordinatively saturated transition metal carbonyl cations by stepwise addition of carbonyl ligands to cationic iron, cobalt, and nickel metal centers. A central theme of this project is the investigation of electron localization around the 18-valence-electron count that is scanned by systematic variation of the metal center and the number of carbonyl ligands in gas-phase transition metal carbonyls. This approach will allow us to follow, in detail, the formation of molecular orbitals and to investigate donation and backdonation by quantum-chemical calculations in order to study the interplay of electronic structure and coordinative saturation in coordination entities of 17, 18, and 19 valence electrons.

For comparison with experimental data, the species of interest will be prepared by means of magnetron sputtering and gas-phase ion chemistry. X-ray absorption and XMCD spectra of these complexes will be recorded with our cryogenic ion trap setup at BESSY II.

This PhD project foresees extended stays in the Department of Molecular Theory and Spectroscopy (F. Neese, D. Manganas) at Max-Planck Institut Mülheim for thorough training in theoretical methods and program packages. The PhD student/doctoral researcher will work closely with a team of postdoctoral research associates and doctoral students at MPI and HZB. The project leaves room for individual explorations based on the interest of the successful candidate.