Measurement of CH density In a pulsed-dc hydrocarbon-gas-mixture discharge

摘要

Optical and electrical measurements are performed in methane/diluent mixtures in a 250-ns pulsed-dc discharge using a fast-rise-time pulser. In particular, emission and laser-induced-fluorescence studies of CH produced by direct-electron-impact dissociation reveal the postdissociation kinetics of CH as well as a means of estimating the CH density. In a 20-Torr 10% /20% /70% mixture of argon/methaneitrogen, the instantaneous CH density is determined to be 2.1 X 10~(13) cm~(-3) at the end of the steady-state voltage and current condition. Kinetics analysis reveals that neutral chemistry with methane is the largest loss process for the CH fragments. Analysis of N_2(C-B) rotational temperatures indicates that less than 30% of the input electrical energy is deposited as heat in the gas, with the balance going toward dissociation, excitation of internal molecular states, and ionization.