Fritz-Haber-Institut der Max-Planck-Gesellschaft
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Liquid Jet Photoelectron Spectroscopy

We investigate the details of intermolecular interactions between molecules in solution or at the interfaces between liquid/gas or liquid/solid state using different variations of liquid-jet photoelectron spectroscopy. We focus on the electronic structure of the ground-state solution and on radiation induced electron dynamics revealing how on a few-femtosecond time scale energy and charge is transferred between solute and solvent. Such electronic structure information is essential for a better understanding of chemical reactions in solution and at interfaces. Interpretations of our experimental data as well as continuous development of the experimental technique are strongly governed by collaboration with theory and complementary experimental groups. Some of our current and continuous research projects are listed below.

Water is one of the most ubiquitous molecules throughout natural sciences, yet the seemingly simple molecule also constitutes one of the most challenging systems to understand. We study the very fundamental properties of liquid water from hydrogen-bond networks to charge and proton transfer processes.
The liquid jet technique opens a window for studying electronic structure properties of biomolecules in their natural aqueous environment. This enables us to study how the bonding networks of biomolecules respond to changes in the environment such as pH or concentrations, and to investigate complex processes such as radiation damage of DNA or ATP hydrolysis.
Aqueous nano-particles represent an interesting example of the solid-liquid interface. We study how interfacial interactions and reactions evolve all the way from aggregation through to nucleation, thus allowing us to identify important intermediate species.
Chiral species exist in two non-superimposable mirror-image structures that respond differently towards circularly polarized light; in photoionization by circularly polarized light this is manifested as a strong forward/backward asymmetry of the ejected electron. We explore how a liquid environment can affect the dichroic properties of chiral solutes, and how intermolecular interactions with the solvent can extend the chiral system.
Liquid ammonia is a particularly interesting counterpart to liquid water; liquid ammonia possesses a different hydrogen-bonded network, and interestingly, liquid ammonia can accommodate high concentrations of long-lived solvated electrons. Together with collaborators we are building a liquid-jet setup capable of hosting a microjet of liquid ammonia, thus allowing for interesting spectroscopy on solvated electrons, complementary hydrogen bond networks, etc.
Gas-liquid interfacial dynamics and reactivity are highly interesting from fundamental and from atmospheric research perspectives; we focus in particular on energy and matter exchange between the two phases during their interactions. We employ different experimental setups (crossed-beam scattering or gas streaming around cylindrical jets) to vary the conditions for the interfacial dynamics. As an example we study how CO2 can be captured by a water/ethanol-amine mixture with which the CO2 molecules react in the solution.