Research Group Prof. Dr. G. Friedrichs

Heatable Photolysis Flow Reactor

In many cases, a sensitive and time-resolved detection system capable of measuring various kinds of reacting species (atoms, radicals, molecules) is needed for investigating the kinetics of chemical reactions. With such an instrument the rate constant of a single elementary reaction as well as the product distribution of the reaction can be measured. This information is useful for developing - step by step - complex reaction mechanisms which are needed for the understanding of practically important chemical processes. Examples stem from the field of combustion (ignition, pollutant formation), atmospheric chemistry (ozone layer, pollutant degradation), chemical vapor deposition (CVD), and exhaust gas cleaning technologies (DeNOx, Reburning). With a detailed reaction mechanism it is possible to model and, where applicable, to optimize these processes.


ms-bildMass spectrometry (MS) is a quite universal detection method for measuring all different kinds of species by "weighing" its masses. The five basic parts of any mass spectrometer are: a vacuum system; a sample introduction device; an ionization source; a mass analyzer; and an ion detector. The sample, a mixture of different components in the gas phase, is ionized (and fragmented) in a high-vacuum chamber. The ionized, charged particles are directed electrostatically into a mass analyzer, separated according to their mass (m/e ratio) and are finally detected. The Figures illustrate our experimental setup that couples laser photolysis with time-resolved mass spectrometric detection. Through a pinhole in the heatable flow reactor part of the reaction gases continuously expand into a differentially pumped vacuum chamber and are analyzed by electron impact ionization and quadrupole mass filtering. Radicals are formed by excimer laser photolysis. Data sampling and spectrometer operation are automated and controlled by a PC. As apparent from the photo of the experimental setup, the test gas mixtures were prepared in a gas manipulation system made out of glass and were sampled through calibrated mass flow controllers.

Contributing researchers: G. Friedrichs, J. Gripp, F. Temps and (formerly) G. Eshenko, C. Kerst, T. Köcher