DIAGNOSTICS
Plasmas as chemistry labs
The smaller a plasma, the larger the experimental setup needed to study it. It is worth the effort, because the reaction conditions found in cubic-millimetre-sized plasmas are very much unique. Even though plasmas at atmospheric pressure are often only a few cubic millimetres in size, they pack quite a punch. This is because special non-equilibrium states can be set up in them, which facilitate physical and chemical processes that are not possible in any other environment. The plasma thus becomes a special kind of laboratory, where atoms and molecules can be excited without their surroundings heating up. “Such excitations could theoretically also be generated in a gas, but to do so we would have to heat it to several thousand degrees Kelvin. As a result, the molecules would decompose,” explains Professor Uwe Czarnetzki, Head of the Chair of Plasma and Atomic Physics at the Faculty of Physics and Astronomy. For many years, he and his team have been developing methods to explore the processes inside plasmas and to characterise the plasmas. Plasmas boast a unique feature: electric fields can be used to supply energy to the electrons in the plasma; the electrons in turn interact with molecules such as nitrogen or carbon dioxide while transferring the energy to them. The molecules are excited, and this happens without the environment heating up in the process, as would be the case in a gas. The molecules that are excited to vibrate have a much higher reactivity than those in the ground state. Plasma can therefore change chemistry or even enable certain chemical processes in the first place. Consequently, plasma provides basic researchers with a unique opportunity to study the excitation of molecules and the associated chemistry beyond thermodynamic equilibrium. Uwe Czarnetzki is therefore primarily interested in the vibrational states of molecules in plasmas.
Due to the current situation, this year's summer school did not take place at the usual location of the physics center in Bad Honnef, but online. The regular programme consisting of basic plasma physics lectures combined with a master class on special topics could not take place as usual. Nevertheless, all teachers have agreed to deliver their basic lectures via an online video format. The summer school was extended to two weeks with two lectures per day. This year more people were able to tune in, because the online format is much easier to reach from regions with limited travel possibilities.
