Interaction of XUV Radiation with Atoms, Molecules and Clusters (FERMI)

A primary goal in both chemistry and physics is to map the energetics and dynamics of molecular reactions on their corresponding timescales. Sample systems and molecular processes come from a wide range of different fields and correspondingly the relevant timescales can cover many orders of magnitude. Examples include the dynamics of proteins folding and unfolding in molecular biology, proton transfer reactions important in atmospheric or radiation chemistry as well as nonadiabatic dynamics in excited or ionized molecules.

The recent progress of extreme ultraviolet (XUV) and X-ray free electron lasers (FELs) has opened up many new and exciting possibilities to study reaction dynamics in real-time. Such studies complement static studies using synchrotron radiation with information on the dynamics of the observed processes. This includes processes triggered by the ionization of a molecular sample with XUV radiation as well as the observation of optically-driven reactions by XUV photoelectron spectroscopy.

In this project we use radiation from large-scale research facilities, including synchrotron light sources and free electron lasers, to conduct studies on molecules and molecular clusters. Examples include molecular dissociation reactions after XUV ionization and double ionization of molecules as well as electronic relaxation processes involving solvated electrons in molecular clusters.

A specific focus is currently on microsolvated biomolecules, i.e. complexes of small biomolecular building blocks like amino acids and nucleobases with water molecules. After XUV ionization from the inner valence shell of such complexes, these systems can emit slow secondary electrons via various non-local autoionization processes. One aim of this project is the study of the energetics and dynamics of these non-local autoionization mechanisms that are of high relevance for an understanding of how radiation damages biological materials.

Schematic representation of secondary electron production via intermolecular Coulombic decay (ICD): 1. An electron is removed from the inner valence shell of a water molecule. 2. In an ICD process the created water cation energetically relaxes by transferring its excess energy to the neighboring thymine molecule, which emits a secondary electron. 3. In a Coulomb explosion the now doubly-charged molecular complex dissociates with a high kinetic energy release.

Contact:

Dr. Sebastian Hartweg

Prof. Dr. Frank Stienkemeier

Funding:

Deutsche Forschungsgemeinschaft

RTG DynCAM