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I will present 3 different research directions that we will build up at Stockholm.
Catalysis is central for many chemical energy transformations that occur at interfaces. One of the dreams is to follow catalytic reactions in real time from reactants over various intermediates to products. The prospective for the study of chemical reactions on surfaces using x-ray free-electron lasers with femtosecond time resolution will be presented together with the first results of CO desorption and CO oxidation. Here new instruments will be constructed that can be used at various future x-ray laser sources.
One of the challenges in catalysis is that reactions occurs at much higher pressures than that what is typically accessible with normal surface physics instrumentations. Recent development in differently pumped photoelectron spectrometer systems currently allows pressures to reach around 10 mbar. However, many of the essential catalytic reactions for our society such as ammonia synthesis or fuel productions take places at pressures around 10 bar or above. A challenge for the future is to develop instrumentation that brings high surface sensitivity for in-situ studies at these high pressures.
Water is the key compound for our existence on this planet and it is involved in many important physical, chemical, biological and geological processes. Although water is the most common molecular substance it is also most unusual with many anomalies in its thermodynamic properties such as compressibility, density variation and heat capacity. The deviation of these properties is strongly enhanced upon supercooling water below the freezing point. Here, we demonstrate a new, general experimental approach to study the structure of liquid states at supercooled conditions below their limit of homogeneous nucleation.
We have used femtosecond x-ray pulses generated by the LCLS x-ray laser to probe evaporatively cooled droplets of supercooled bulk water and find unambiguous experimental evidence for the existence of metastable bulk liquid water down to temperatures of 227 K in the previously largely unexplored “no-man’s land”. There is a hypothesis that these anomalies originate from a critical point deep in the supercooled regime at some unknown high pressure. In the future it is therefore essential to develop experiments that can perform the same type of fast cooling and ultrafast probing under high pressures and search for liquid-liquid transitions and a critical point.