A pioneering experiment for the study of reaction networks in flames by using Photoelectron Photoion Coincidence (iPEPICO) spectroscopy was realized at the Synchrotron Light Source (SLS) from the Paul Scherer Institute (PSI). This new analytical tool for the investigation of reaction networks was developed and applied to questions regarding chemical reaction-kinetics in collaboration with Prof. Dr. Tina Kasper from the University Duisburg-Essen.
The experiment combines a molecular beam flame sampling setup with the analytical possibilities of the iPEPICO technique – both being two highly-sensitive and specialized diagnostic methods. The combination of these techniques is characterized by the possibility of a comprehensive, quantitative and isomer selective analysis of reaction intermediates occurring in the combustion process. Conclusively, it provides a new analytical dimension with high precision and sensitivity.
In detail, synchrotron radiation for soft single photoionization is used to determine the mass of an ionized particle in coincidence with the energy of the corresponding electron. Key to this experiment is the light source providing a high energy output with tunable wavelength over a broad range (here 4 – 20 eV). For applying the iPEPICO setup in combustion environment, the University of Duisburg-Essen has developed a combustion chamber housing a one-dimensional flat flame and a molecular beam interface. The combustion chamber design can be coupled to the iPEPICO spectrometer of the VUV-beamline. In general, the instrument is well suited for the investigation of chemical reaction networks in flames. Intermediate species in combustion processes can be studies and quantified, while the setup is particularly suited for detecting radical species. The superior identification capabilities are demonstrated for the isomeric species propine / propadiene (see figure).
The iPEPICO combustion setup is a significant addition to the institute’s core activities like fuels and pollutants and combines scientific fundamental research with wider generic societal issues. Current studies are particularly focused on the initial formation of fuel radicals and their branching ratios i.e. the first steps in the fuel decomposition mechanism. The activities are funded by the DFG project “PEPICO in combustion research”.