Spectroscopy of molecular processes (FS-SMP)

Welcome to the “Spectroscopy of Molecular Processes” group!

We develop modern spectroscopic techniques to analyse complex molecules and molecular mixtures, aiming at a detailed understanding and control of chemical processes at the molecular level. The group is part of the “Photon Science” division at DESY and also integrated into the Institute of Physical Chemistry at the Christian-Albrechts-Universität zu Kiel and the Center for Molecular Water Science (CMWS), which is a bottom-up initiative with more than 40 national and international partners.

Our main expertise is on molecular rotational spectroscopy in the gas phase. Modern broadband rotational spectroscopy using chirped microwave pulses provides us high-level structures of molecules and molecular complexes, but also studies of molecular dynamics and tunneling processes become possible. Our research can be roughly divided into three research areas, which are strongly interconnected.

1. We are interested in unraveling non-covalent intermolecular interactions at play in molecular recognition. We want to understand in detail, which forces determine how molecules bind to each other. For this, we study model complexes under isolated conditions in the gas phase. A special emphasis is put on the interplay between dispersion interactions and hydrogen bonding, i.e., highly non-directed vs. directed binding. We complement these studies with modern quantum-chemical calculations. Another research interest in this subgroup is micro-solvation. We study molecules surrounded by increasing amounts of water molecules in order to learn how both the solute and the solvent network adjust their structures to maximize intermolecular interactions.

2. In a second research theme, we develop methods to investigate chiral molecules, which are at the heart of all of biochemistry. Using microwave three-wave mixing, a chirality-sensitive rotational spectroscopy approach, the two enantiomers of chiral molecules can be differentiated. Furthermore, in a recent extension, controlled and enantiomer-selective population transfer could be achieved. One aim of these research activities is to separate chiral molecules, for example to then exploit them for precision measurements.

3. More than 200 molecules have been identified in the interstellar medium (ISM) till today. Most of the detections were based on a combination of radioastronomy and rotational spectroscopy. They exploit the fingerprint character of rotational spectroscopy. In astrochemistry, we want to understand which chemical processes occur in interstellar space, which is characterized by extreme conditions such as low temperature and harsh radiation, and why. It is one of the main themes of astrochemistry to unravel the underlying chemical processes, both in the gas phase and on tiny ice grains, which are supposed to be valuable reaction centers in space. These topics are investigated in our astrochemistry subgroup. In addition to high-level rotational spectroscopy studies, we also actively exploit modern light sources, such as PETRAIII and FLASH at DESY, FELIX in Nijmegen, the Netherlands, and SOLEIL in Orsay, France, to understand how polycyclic aromatic hydrocarbons (PAHs), one of the prominent molecule classes in the ISM, react under harsh radiation.

We operate four molecular-beam rotational spectrometers in our laboratory (three broadband chirped-pulse rotational spectrometers covering the frequency ranges 2-18 GHz, 18-26 GHz, and 75-110 GHz, respectively, and a high-resolution cavity spectrometer from 6-20 GHz. A molecular-beam IR-UV spectrometer is currently being set up. The broadband rotational spectrometer operating in the W band frequency range (75-110 GHz) is optimized for measurements of room-temperature samples to study molecules in vibrationally excited states, for example.

Our research is funded by the Deutsche Forschungsgemeinschaft via a project in the Sonderforschungsbereich 1319 “Extreme light sensing of chiral molecules”, ELCH, at the U Kassel, a project in the Schwerpunktprogramm 1807 “Control of London dispersion interactions in molecular chemistry”, and (until April 2020) via the ERC Starting grant “ASTROROT”.

For more Information regarding the ELCH consortium, click here.

For more information regarging the SPP programm, click here.

We are a very international group and have regular visitors from Universities and research institutions all over the world. If you are interested in one or several of the above mentioned topics and interested in joining us, please get in touch with us.