Influence of hydrocarbons on vibrational excitation of H2 molecules

The influence of light hydrocarbons on vibrational excitation of H2 generated in a special source of excited molecules has been studied. Molecule dissociation on the hot tungsten filament and atom recombination on cooled walls is used for the production of molecular excitation in the source. Specific influence of CH4, C2H4 and C2H6 on vibrational distribution of hydrogen molecules from the source is presented here. Production of vibrationally excited H2 molecules due to the thermal dissociation on the hot filament is observed when C2H4 (ethene) and C2H6 (ethane) are introduced alone in the source. These molecules appear to be produced by direct process on the hot filament in the case of ethene while in the case of ethane H2(v)H2(v) is produced by the similar process as for H2. Production of H2(v)H2(v) is not observed when only CH4 is introduced into the source. In this case vibrational relaxation of H2(v)H2(v) is observed when CH4 is introduced into the source in addition to H2. Studied processes are relevant for the modelling of edge plasma in tokamaks.