Speaker
Description
Liquid-vapor interfaces drive numerous important processes in the environment and technology, such as the sequestration of CO2 by the oceans and the uptake and release of trace gases by aerosol droplets. Our understanding of the physical and chemical properties of liquid-vapor interfaces under realistic environmental and operating conditions on the molecular scale still falls far short of what has been achieved for solid-vapor interfaces over the past decades. This limitation still hampers the development of, e.g., more precise climate models.
The main reason for this situation is the often vastly greater difficulty in the preparation of liquid-vapor interfaces (compared to solids) with controlled properties and their investigation with high interface specificity under realistic conditions. This is partly due to the spatial fluctuations in the position of the interface and the fast diffusion from the interface into the bulk and vice versa. In addition, traditional (vacuum-based) methods for the preparation of clean surfaces are not applicable for liquid-vapor interfaces. We are thus facing the double challenge to move forward with the investigation of these critical interfaces with increased fidelity while in parallel developing new methods for their preparation and interrogation.
Two new instruments will address these scientific and technological challenges through a combination of soft X-ray and IR based spectroscopies. While core-level spectroscopy (e.g., APXPS) provides information on the elemental and chemical composition at the interface, IR spectroscopy (here in particular RAIRS) yields complementary information about the orientation and bonding of molecules at the liquid-vapor interface, expands the pressure range of the operando experiments, and provides an excellent method to monitor possible radiation-induced damage to the interface and surrounding media in X-ray based spectroscopies.
This concept will be realized in a laboratory-based instrument at the FHI and also in a new dipole magnet beamline at BESSY. While the laboratory-based instruments allows the simultaneous investigation of the interface by APXPS and RAIRS from adjacent sample areas, the new beamline at BESSY will use IR radiation from the storage ring which can be focused to the same spot size as the X-rays, thus enabling simultaneous measurements from the same sample location. The modular concept of the beamline instrument also opens up opportunities for investigations of other interfaces, such as solid-liquid and solid-vapor.
