H− production in hydrogen DC glow discharge Article Swipe
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· 2024
· Open Access
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· DOI: https://doi.org/10.1088/1361-6595/ad57ed
· OA: W4399611071
The H − ion dynamics in the positive column of H 2 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 H 2 vibrational temperature was estimated by comparing measured and simulated H 2 VUV absorption spectra. The analysis of the experimental dependencies of H − and H/H 2 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 H 2 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 H 2 ( 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 H 2 − (X 2 Σ u + ) only at low E/N. At high E/N, the H – production mostly occurs via the excitation of high-energy H 2 − states, such as H 2 – (B 2 Σ g + , A 2 Σ g + , C 2 Π u ) and Feshbach resonances similar to H 2 − ( 2 Σ g + ) Rydberg state.
