Energetic ion, atom, and molecule reactions and excitation in low-current H{sub 2} discharges: Spatial distributions of emissions
- JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309-0440 (United States) and Institute of Physics, University of Belgrade, P.O. Box 86, 11080 Zenum, Belgrade (Serbia)
Spatial distributions of H{sub {alpha}}, H{sub {beta}}, and the near-uv continuum emission from the H{sub 2} a {sup 3}{sigma}{sub g}{sup +} state are measured and compared with a model for low-current electrical discharges in H{sub 2} at high E/N and low Nd, where E is the spatially uniform electric field, N is the gas density, and d is the electrode separation. Data are analyzed for 300 Td<E/N<45 kTd, d=0.04 m, and 2x10{sup 21}<N<2.6x10{sup 22} m{sup -3}. (1 Td=10{sup -21} V m{sup 2}) The excitation is produced by electrons and by hydrogen atoms and molecules with mean energies from 5 to 1500 eV. Electron-induced emission, dominant at low E/N and low pressures, is distinguished by its buildup toward the anode. Excitation of H{sub {alpha}} by fast H atoms dominates at high E/N and increases toward the cathode. The observed H{sub {alpha}} emission at low E/N is normalized to previous experiments to yield absolute experimental excitation coefficients for all E/N and Nd. Small adjustments of model parameters yield good agreement with H{sub {alpha}} data. Cross sections are derived for excitation of the H{sub 2} near-uv continuum by H atoms. Spatial and pressure dependencies of H{sub {alpha}} and H{sub 2} near-uv emissions agree well with a model in which reactions of H{sub 2}{sup +}, H{sub 3}{sup +}, and H{sup +} ions with H{sub 2} lead to fast H atoms and H{sub 2} molecules, which then excite H atoms or H{sub 2} molecules.
- OSTI ID:
- 21294256
- Journal Information:
- Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics (Print), Vol. 80, Issue 1; Other Information: DOI: 10.1103/PhysRevE.80.016408; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1539-3755
- Country of Publication:
- United States
- Language:
- English
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