Initial Processes in CO2 Glow Discharges

Abstract

Initial dissociation rates of CO2 in pure CO2 glow discharges and CO2 mixtures with He, N2, H2 have been determined in the 1-Torr pressure range using a mass spectrometric sampling technique combined with plasma diagnostic methods. The observed results for the pure CO2 case are discussed in terms of dissociative attachment and collisional dissociation of vibrationally excited CO2 molecules both of which contribute to the dissociation process; most influential in mixtures is H2 which reduces the dissociative process. At the same time, the quasistationary values of the CO2–CO–O2 mixture as well as that of CO2–CO–O2 with He, N2, H2 have been measured: [CO2]/[CO][O2]1/2 is approximately constant at pressures >500 mTorr and linearly dependent upon H2 concentration.