Energetic ion, atom, and molecule reactions and excitation in low-current H{sub 2} discharges: Model

Journal Article · Mon Jun 15 00:00:00 EDT 2009 · Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics (Print)

DOI:https://doi.org/10.1103/PHYSREVE.79.066401· OSTI ID:21294299

Phelps, A V ^[1]

---

1. JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309-0440 (United States)

Models of the elastic, inelastic, and reactive collisions of energetic hydrogen ions, atoms, and molecules are developed for predicting H{sub {alpha}} and H{sub 2} near-uv emission, H{sub {alpha}} Doppler profiles, and ion energy distributions for low-pressure, low-current discharges in H{sub 2}. The model is applied to spatially uniform electric field E to gas density N ratios of 350 Td{<=}E/N{<=}45 kTd and 8x10{sup 19}{<=}Nd{<=}10x10{sup 21} m{sup -2}, where d is the electrode separation and 1 Td=10{sup -21} V m{sup 2}. Mean ion energies at the cathode are 5-1500 eV. Cross sections for H{sup +}, H{sub 2}{sup +}, H{sub 3}{sup +}, H, H{sub 2}, and excited H(n=3) collisions with H{sub 2} and reflection probabilities from electrodes are updated and summarized. Spatial and energy distributions of ions and fast neutrals are calculated using a ''multibeam'' technique. At the lower E/N and Nd, electron excitation of H{sub {alpha}} dominates near the anode. Excitation of H{sub {alpha}} by fast H atoms near the cathode increases rapidly with pressure through a multistep reaction sequence. At higher E/N, fast H atoms produced at the cathode surface excite much of the H{sub {alpha}}. The model agrees with experimental spatial distributions of H{sub {alpha}} emission and Doppler profiles. Ion energy distributions agree with experiments only for H{sub 2}{sup +}. Cross sections are derived for excitation of the near-uv continuum of H{sub 2} by H atoms.

• OSTI ID: 21294299
• Journal Information: Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics (Print), Vol. 79, Issue 6; Other Information: DOI: 10.1103/PhysRevE.79.066401; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1539-3755
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ANODES
ATOM-MOLECULE COLLISIONS
CATHODES
CROSS SECTIONS
DOPPLER EFFECT
ELECTRIC DISCHARGES
ELECTRIC FIELDS
ELECTRONS
ENERGY SPECTRA
EV RANGE
EXCITATION
HYDROGEN
HYDROGEN IONS 1 PLUS
HYDROGEN IONS 2 PLUS
HYDROGEN IONS 3 PLUS
ION-MOLECULE COLLISIONS
MOLECULE-MOLECULE COLLISIONS
REACTION KINETICS
SPATIAL DISTRIBUTION
TAIL IONS