Atomic and molecular surface and volume processes in the analysis of negative hydrogen discharges
The principal source of negative ion generation in hydrogen discharges is now recognized to be low-energy electron attachment to H/sub 2/(/nu//prime//prime/) molecules excited to the middle portion of the vibrational spectrum. Electron excitation processes are generally taken to be the principal source of H/sub 2/(/nu//prime//prime/) generation, with high-energy excitations through the singlet spectrum being the principal excitation process populating the active portion of the vibrational spectrum. A description of the collisional re-excitation from level /nu//prime//prime/, to level /nu//prime//prime/, requires 15 /times/ 15 matrix of cross sections linking all initial and final levels. These cross sections have been evaluated and incorporated into the modelling code. An additional source of vibrational excitation may be derived from recombination of H/sub 2//sup +/ and H/sub 3//sup +/ ions on the surfaces of the discharge. In this case the molecular ions will impinge with kinetic energies given by the plasma potential, 1--10 eV. In this paper we report the evaluation of H/sub 2/(/nu//prime//prime/) resulting from the surface recombination process. The use of low-work-function materials for the discharge surfaces makes possible two additional source of negative ions: the direct formation of negative ions by hydrogen atoms rebounding from the surface, and the dissociation of H/sub 2//sup /minus// ions formed in the surface selvage. A recent paper has demonstrated the efficacy of Ba surfaces as an active medium for H/sup /minus// formation. Here we shall extend our discussion to H/sub 2//sup +/, H/sub 3//sup +/ collisions on Ba surfaces and inventory the generation of H, H/sub 2/(/nu//prime//prime/), and H/sup /minus// rebounding from these surfaces. 16 refs., 4 figs.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5820729
- Report Number(s):
- UCRL-101309; CONF-890697-1; ON: DE89015705
- Resource Relation:
- Conference: NATO Advanced Study Institute on non-equilibrium processes in partially ionized gases, Acquafredda di Maratea, Italy, 4-17 Jun 1989; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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SUPERCONDUCTIVITY AND SUPERFLUIDITY
74 ATOMIC AND MOLECULAR PHYSICS
HYDROGEN IONS 1 MINUS
PRODUCTION
BARIUM
CROSS SECTIONS
DISSOCIATION
ELECTRON ATTACHMENT
HYDROGEN IONS 1 PLUS
ION-MOLECULE COLLISIONS
RECOMBINATION
SURFACES
VIBRATIONAL STATES
WEAKLY IONIZED GASES
WORK FUNCTIONS
ALKALINE EARTH METALS
ANIONS
CATIONS
CHARGED PARTICLES
COLLISIONS
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FLUIDS
FUNCTIONS
GASES
HYDROGEN IONS
ION COLLISIONS
IONIZED GASES
IONS
METALS
MOLECULE COLLISIONS
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