Research

The research within the IMPRS-EPPC focusses on many different aspects of physical chemistry, with a particular emphasis on identifiying the elementary process steps that are ultimately responsible for functionality.

Each university group and FHI department focusses their research efforts on a particular class of systems, scientific questions, and methodologies. Bringing together these different approaches into the overarching concept of the IMPRS-EPPC warrants a universal and interdisciplinary doctoral education program. In the following, the different scientific aspects covered by the School, are summarized.

1.1.1.   Atomistic Length and Time Scales

Primary steps for any chemical or physical functional system, such as a catalyst or opto-electronic device, typically occur at the length scales of single atoms, mole­cules, or chemical bonds and at corresponding ultrafast time scales. Therefore, characterization of the geometric and electronic structure at atomistic length and time scales, as well as the interactions with external stimuli at the single molecule level is indispensable for a microscopic understanding of the mechanisms. Two complementary approaches are employed to achieve such atomistic level understanding: (A) Through analysis on atomistic length scales by (i) studies of isolated single molecules or gas phase clusters or (ii) atomic-resolution micro­scopy, and (B) through time-resolved studies employing (iii) ultrafast spectroscopy techniques.

These complimentary approaches are well represented within the IMPRS-EPPC: The groups of Dopfer, Gühr, Koch, Meijer, and Pagel study (i) isolated molecules or clusters in the gas phase, while the groups of Franke, Roldán, and Wolf employ (ii) atomic-resolution microscopy. Their research program ranges from structural characterization and reaction studies of isolated species in the gas phase (Dopfer, Koch, Meijer, Pagel), quantum manipulation of their properties (Gühr, Koch) to structural properties of molecules and nanostructures at the atomic scale (Franke, Roldán, and Wolf).

On the other end, the groups of Draxl, Ernstorfer, Saalfrank, Stähler, Weinelt, and Wolf are leading experts in (iii) ultrafast spectroscopy. Here, the variety of scientific topics ranges from spin dynamics in ferromagnetic thin films (Weinelt) to charge transfer in organic-inorganic hybrids (Draxl, Stähler) and excitons in two-dimensional materials (Ernstorfer), warranting a unifying theme within the IMPRS-EPPC. The groups of Gühr and Koch combine both ideas by studying the ultrafast dynamics of isolated molecules, and the quantum manipulation thereof, whereas the groups of Franke and Wolf also develop methods for characterization of spatial-temporal resolved processes in scanning probe microscopy.

1.1.2.   From Microscopic Understanding to Complexity

There are multiple approaches for slowly increasing complexity in order to bridge from the fundamental understanding at the atomistic level to real-life conditions of high performance systems. For instance, the group of Roldán employs size- and shape-controlled nanoparticles for catalysis, while the group of Risse provides a detailed understanding of atomic defects in otherwise perfectly controlled single-crystal surfaces.

Most IMPRS-EPPC groups employ advanced spectroscopy techniques to single out (a) certain species from complex mixtures or (b) specific local interactions in complex systems, using the respective specificity. For example, (a) ion-mobility combined with action spectroscopy (Dopfer, Meijer, Pagel) allow to identify and characterize different enantiomers, while (b) chemical shifts in X-Ray spectroscopy (Gühr, Roldán, Weinelt) or surface specific vibrational (Saalfrank, Risse, Wolf) or electron spectroscopies (Ernstorfer, Stähler, Weinelt, Wolf) identify certain reaction mechanisms. Further, the groups of Schlögl and Roldán have developed advanced capabilities to monitor the evolution of catalysts in operando, while the group of Thomas provides extensive expertise in nanostructured materials.

On the theory side, the IMPRS-EPPC faculty members bring in the different microscopic components (Saalfrank: ultrafast surface dynamics, Draxl: organic/ inorganic hybrids, theoretical spectroscopy, Koch: quantum control) as well as the multi-scale modelling competence to bridge across complexity gaps (Draxl, Reuter).

Combining these different levels of investigating processes from microscopic to meso- and macroscopic scales under the roof of the IMPRS-EPPC opens the way to a comprehensive understanding of the processes in physical chemistry, and provides numerous opportunities for fundamentally new discoveries.