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The H− ion dynamics in the positive column of H2 DC glow discharge was studied by the laser photodetachment technique in a wide range of pressure, 0.1–3 Torr, and current, 1–30 mA, which cover a range of E/N from ∼40 Td up to ∼170 Td. Using a partial modulation of the discharge current, it is shown that the H−concentration follows H atom dynamics due to a fast detachment reaction with the atoms; the higher the H density, the lower the H–/ n e ratio. The dynamics of H atom density during discharge modulation was measured by time-resolved actinometry on Ar atoms, while H2 vibrational temperature was estimated by comparing measured and simulated H2 VUV absorption spectra. The analysis of the experimental dependencies of H− and H/H2 on the discharge parameters allowed estimating the effective rate constant of H− production in the discharge as a function of the reduced electric field. For this discharge model, self-consistent state-to-state vibrational kinetics as well as H2 highly excited electronic states were developed. The main processes that contribute to H− production and loss are discussed in detail. Dissociative attachment to vibrationally excited H2(v) molecules is the main channel of H – production but occurs via the excitation of the well-known low-energy (ϵ th ≈ 3 eV) shape resonance of H2−(X2Σu+) only at low E/N. At high E/N, the H– production mostly occurs via the excitation of high-energy H2− states, such as H2–(B2Σg+, A2Σg+, C2Πu) and Feshbach resonances similar to H2−(2Σg+) Rydberg state. [ABSTRACT FROM AUTHOR]

This work presents the results of developing a set of electronic and chemical reactions for a plasma discharge in octafluoropropane (C3F8). Electronic reactions were obtained using the most relevant set of cross sections at the moment, taking into account experimentally known dissociation and ionization channels. Based on the dissociation products obtained during electronic reactions, a set of chemical reactions was adapted by analogy with the C4F8 reaction scheme from the literature. Next, the resulting complete set of reactions was tested against published experimental data on the concentration of electrons, negative ions, and electronegativity in a capacitive plasma discharge at different gas pressures and discharge input powers. For this purpose, a one-dimensional hydrodynamic drift-diffusion model was used. Reasonable agreement was obtained between the model and experimental data on electronegativity. Eventually, the resulting set of reactions was adapted for a two-dimensional hydrodynamic drift-diffusion model of an ICP discharge. The results of the calculations are two-dimensional distributions of radicals and ions, radical and ion composition of fluxes onto the substrate under conditions typical for industrial reactors. [ABSTRACT FROM AUTHOR]