Magnetfeldabhängige Mikrowellen-Absorption und -Dispersion zur Bestimmung von Stoßfrequenz und Stoßmodell bei Flammenplasmen

At atmospheric pressure acetylene-oxygen and acetylene-air flames were burning through anX-band waveguide resonator parallel to the microwave electric field vector and perpendicular to an external magnetic field in the Voigt-geometry commonly used to study electron cyclotron resonance. However, because the electron collision frequency is greater than the angular microwave frequency, absorption and dispersion are merely slowly decreasing functions of the magnetic field strength. They depend—besides on collision frequency—on the nature of the electron collisions. Both, absorption and dispersion were evaluated independently for different classical collision models. Taking into account the tensor-property of conductivity, closest agreement of the two results for the collision frequency and best coincidence of measurement and theory was obtained for the model of an electron-polarizable molecule collision, which corresponds to a collision frequency independent of electron velocity. The collision frequency amounts to 210±4 GHz for our acetylene-oxygen-flames and 249 ± 4 GHz for the acetylene-air-flames.