Recombination of non-equilibrium plasma in water vapor- and hydrocarbon-containing mixtures

The kinetics of non-equilibrium discharge plasma when the ion composition is dominated by water or hydrocarbon ions is discussed. Plasmas with water ions are formed in atmospheric discharges and discharges in the presence of liquid water or water vapor, including plasma applications for air purification, medicine and combustion. Reactions with hydrocarbon ions play an important role in interstellar chemistry, plasma enhanced chemical vapor deposition, synthetic diamond film deposition and plasma assisted combustion. The modeling of water ion chemistry and chemistry of hydrocarbon-containing plasmas requires large amount of data on the rates of ion formation and loss. Particular attention is given to cluster ions, which are important at not-too-low gas pressures, whereas the majority of studies of ion-molecule reactions have been performed at low pressures in the absence of cluster ions. To illustrate importance of the described processes, the development of streamer discharges in long humid air gaps are discussed and the influence of water ions on the streamer properties is demonstrated. In addition, the decay of non-equilibrium plasma with water and hydrocarbon ions is analyzed in combustible gaseous mixtures excited by a repetitively pulsed nanosecond discharge.