Recombination and dissociation of H sub 2 sup + and H sub 3 sup + ions on surfaces to form H sub 2 ( v double prime ): Negative-ion formation on low-work-function surfaces

Journal Article · Fri Jun 01 00:00:00 EDT 1990 · Journal of Applied Physics; (USA)

DOI:https://doi.org/10.1063/1.345095· OSTI ID:6807398

Hiskes, J R; Karo, A M ^[1]

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1. Lawrence Livermore National Laboratory, University of California, Livermore, California 94550 (USA)

The recombination and dissociation of H{sup +}{sub 2} and H{sup +}{sub 3} ions incident upon metal surfaces leads to H, H{sub 2}({ital v}{double prime}), and H{sup {minus}} products rebounding from the surface. A four-step model for H{sup +}{sub 2} -ion recombination generates H{sub 2}({ital v}{double prime}) via resonant electron capture through the {ital b} {sup 3}{Sigma}{sup +}{sub {ital u}} and {ital X} {sup 1}{Sigma}{sup +}{sub {ital g}} states. A molecular trajectory analysis provides final-state H{sub 2}({ital v}{double prime}) distributions for incident energies of 1, 4, 10, and 20 eV. The calculated H{sub 2}:H{sup +}{sub 2} yields compare favorably with the observed yields. A similar four-step model for incident H{sup +}{sub 3} proceeds via resonant capture to form the H{sub 3}(2{ital p} {sup 2}{ital E}{prime}{r arrow}2{ital p} {sup 2}{ital A}{sub 1}) ground state, in turn dissociating into H+H{sub 2}({ital v}{double prime}), with the fragment molecule rebounding to give the final H{sub 2}({ital v}{double prime}) distribution. Comparing the final populations {ital v}{double prime}{ge}5 for incident H{sup +}{sub 2} or H{sup +}{sub 3} shows that the H{sup +}{sub 3} ion will be more useful than H{sup +}{sub 2} for H{sup {minus}} generation via dissociative attachment. Molecular ions incident upon low-work-function surfaces generate additional H{sub 2}({ital v}{double prime}) via resonant electron capture through excited electronic states and provide two additional sources of H{sup {minus}} production: Direct H{sup {minus}} production by H dissociation products rebounding from the surface and H{sup {minus}} production through the formation of H{sup {minus}}{sub 2} in the surface selvage that in turn dissociates into H+H{sup {minus}}.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6807398
• Journal Information: Journal of Applied Physics; (USA), Journal Name: Journal of Applied Physics; (USA) Vol. 67:11; ISSN 0021-8979; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
656003 -- Condensed Matter Physics-- Interactions between Beams & Condensed Matter-- (1987-)
74 ATOMIC AND MOLECULAR PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANIONS
CAPTURE
CATIONS
CHARGED PARTICLES
COLLISIONS
DISSOCIATION
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FUNCTIONS
HYDROGEN IONS
HYDROGEN IONS 2 PLUS
HYDROGEN IONS 3 PLUS
IONS
METALS
MOLECULAR IONS
MOLECULE COLLISIONS
NICKEL
RECOMBINATION
RESONANCE
SURFACES
TRANSITION ELEMENTS
VIBRATIONAL STATES
WORK FUNCTIONS