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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of the H2 vibrational distribution in a hydrogen discharge (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 508-510 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The H2(v‘) vibrational distribution observed in a medium-density hydrogen discharge is analyzed in terms of standard collisional processes. All processes in the model are specified independently of adjustable parameters. The calculated distribution is found to be a sensitive function of the wall relaxation process. The warm-gas-temperature discharge analyzed here leads to a substantially more rapid H2(v‘) wall relaxation than is inferred from cold-gas systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100914
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  • 2
    Electronic Resource
    Electronic Resource
    Optimum extracted negative-ion current densities from tandem high-density systems (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 1759-1764 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A tandem high-density hydrogen negative-ion-source system is optimized for the purpose of identifying the maximum possible extracted ion current densities. In the first chamber, vibrational excitation occurs by high-energy electron excitation (E-V process); in the second chamber negative ions are formed by dissociative attachment. The electron, atom, and molecular densities are varied together with the length of the second chamber. Electron excitation cross sections to the B1∑u and C1∏u states are calculated as a function of vibrational excitation. The vibrational excitation approaches an asymptotic value as the first-chamber electron density increases. For a system with scale length R=10 cm the optimum extracted current densities occur for gas densities near 1015 mol cm−3 for first-chamber electron densities equal to 1013 cm−3, and for second-chamber electron densities in the 4–6×1012 cm−3 range. For atomic densities equal to one-tenth the molecular density and for second-chamber scale lengths as short as Z/R=0.2, extracted current densities are approximately 30 mA cm−2. As Z/R decreases toward 0.1, the current density is doubled. If the atomic density is increased to one-fifth the molecular density, these current densities are halved; for atomic densities equal to the molecular density, these current densities are reduced by a factor of 6. Applying the system scaling law and varying R from 10 cm toward 1 cm, the extracted current densities tend toward several hundred mA cm−2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336025
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  • 3
    Electronic Resource
    Electronic Resource
    Recombination and dissociation of H2+ and H3+ ions on surfaces to form H2(v‘): Negative-ion formation on low-work-function surfaces (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6621-6632 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The recombination and dissociation of H+2 and H+3 ions incident upon metal surfaces leads to H, H2(v‘), and H− products rebounding from the surface. A four-step model for H+2 -ion recombination generates H2(v‘) via resonant electron capture through the b 3Σ+u and X 1Σ+g states. A molecular trajectory analysis provides final-state H2(v‘) distributions for incident energies of 1, 4, 10, and 20 eV. The calculated H2@B:H+2 yields compare favorably with the observed yields. A similar four-step model for incident H+3 proceeds via resonant capture to form the H3(2p 2E'→2p 2A1) ground state, in turn dissociating into H+H2(v(underbar)‘), with the fragment molecule rebounding to give the final H2(v‘) distribution. Comparing the final populations v‘≥5 for incident H+2 or H+3 shows that the H+3 ion will be more useful than H+2 for H− generation via dissociative attachment. Molecular ions incident upon low-work-function surfaces generate additional H2(v‘) via resonant electron capture through excited electronic states and provide two additional sources of H− production: Direct H− production by H dissociation products rebounding from the surface and H− production through the formation of H−2 in the surface selvage that in turn dissociates into H+H−. The H−2 in the selvage is formed by resonant capture to the low-lying vibrational levels of H2(v‘), and complements dissociative attachment to high-lying levels in the discharge. The H, H2(v‘), and H− yields are inventoried for H+3 incident upon barium surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345095
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  • 4
    Electronic Resource
    Electronic Resource
    Shock dynamics in the sub-nanometer femtosecond domainWork performed in part under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract number W-7405-ENG-48 and under the auspices of the Office of Naval Research. (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 277-289 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New experimental techniques combined with computer molecular dynamics simulations of increasing complexity are beginning to permit a detailed examination of the initial steps in the complex chemistry describing the high-temperature, high-pressure regime associated with combustion and detonation as well as processes that may be involved in shock-induced chemistry. We present the results of several simulations that describe the generation of moderately strong shocks and their interaction with molecules embedded in weakly-bound clusters, with material defects such as microscopic voids, and with molecular species placed in the neighborhood of such defects.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382428
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulations of energy transfer in shocked molecular systems (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 30 (1986), S. 763-765 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560300765
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of lasers on experimental and theoretical studies of second order Raman spectra (1981)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 10 (1981), S. 229-233 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The history of experimental and theoretical studies of second order Raman spectra is illustrated by studies that have been made on sodium chloride. It is shown how the introduction of polarized laser sources radically transformed the experimental situation by demonstrating that the observed spectra are highly sensitive to scattering geometry and drastically different from previous results obtained using unpolarized mercury are sources. This necessitates abandonment of previous interpretations of these spectra as simple maps of the two-phonon joint density of states. Results are presented which show how the inclusion of the Raman polarizability in the scattering calculations, using a simple phenomenological model, also dramatically alters the predicted spectra. Moreover, it does so in such a way as to produce the same degree of agreement between theory and experiment as existed between the earlier spectra and the joint density of states. A short overview of attempts to refine the theory further is presented. It is concluded that subsequent extensions of phenomenological and semi-phenomenological theories, amied at producing a precise fit to the observed spectra, are not satisfactory. It is therefore argued that attempts be made in the future to derive the Raman polarizabilities from first principles.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250100146
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    Paper (German National Licenses)
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