Analysis of decomposition process of BrCN with microwave discharge flow of Ar

Abstract

CN(X 2Σ+) radicals were produced from the dissociative excitation reaction of BrCN with the microwave discharge flow of Ar. This plasma reaction was studied by the combined analysis of the laser-induced fluorescence (LIF) and electrostatic-probe measurements. The Ar pressure, PAr, was in the range 0.2–0.5 Torr. The absolute densities of CN(X 2Σ+) radicals, nCN(X), and that of the metastable state of Ar atoms, nM, were determined by observing the CN(A 2Πi–X 2Σ+) and Ar(3P1–3P2) transitions, respectively. The temperature, Te, and the density, ne, of free electrons were determined from the electrostatic-probe measurement. When a trace amount of H2O vapour was introduced into the reaction system, nCN(X), nM, Te and ne were varied. By comparing the decrements of nCN(X), nM and ne upon the addition of H2O vapour into the reaction system, the production process of CN(X 2Σ+) was found, predominantly, to be the energy transfer from the metastable state of Ar atoms.