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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3190-3197 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The decay rate of the Hg 61P1 level was measured as a function of cold spot temperature (Hg density) and buffer gas pressure in cylindrical, sealed fused silica cells. The decay rates were obtained using a time-resolved laser-induced 185 nm fluorescence experiment with multi-step excitation. Cold spot temperatures from 25 to 100 °C were studied. The Hg densities for this temperature range and with no buffer gas yield the lowest possible decay rates due to radiation trapping with partial frequency redistribution. Decay rates with argon buffer gas pressures of 3 and 30 Torr were also studied. The results are in agreement with published data from a discharge afterglow experiment. Monte Carlo simulations of radiation transport in the cells, including the effects of hyperfine and isotope structure, the effects of foreign gas broadening, and partial frequency redistribution are compared to the experimental data. Reasonably good agreement is obtained, however there is evidence of quenching of Hg 61P1 atoms in collisions with ground state Hg and Ar atoms. An analytic formula for the fundamental mode trapped decay rate of the 61P1 level, which is applicable over a substantial region of parameter space, was devised from the Monte Carlo results. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1546-1554 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The gas temperature in a hot filament activated diamond chemical vapor deposition system is derived from the vacuum ultraviolet absorption spectrum of the H2 molecule. Curves of growth for the optically thick spectra are calculated using a Voigt line shape and published oscillator strengths in order to measure relative populations of H2 in various rotational and vibrational levels of the ground electronic state. The H2 vibrational levels are nearly in equilibrium. The gas temperature field is most strongly influenced by the substrate temperature. Heat conduction from the filament produces a large temperature gradient near the filament. Heat released or absorbed in gas phase hydrocarbon chemical reactions does not significantly affect the temperature field. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3142-3150 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The methyl radical density, acetylene mole fraction, filament properties, and diamond growth rate and film quality are measured in a hot filament chemical vapor deposition system when C2H2 and H2 are used as the input gases. The methyl radical density and acetylene mole fraction depend greatly on the degree of filament surface poisoning. This poisoning prevents diamond growth due to a lack of hydrogen atoms and/or methyl radicals. Understanding the large influence of the filament surface catalytic characteristics is important for developing a gas phase model of this system. The results obtained with C2H2 and H2 as the input gases are compared to those obtained with CH4 and H2 as the input gases. Under conditions when the filament surface is not poisoned, the methyl radical concentrations are similar when either C2H2 and H2 are the input gases or when CH4 and H2 are the input gases.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1900-1904 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The column densities of several molecular radicals are measured in an oxyacetylene torch flame during the growth of diamond films. The column densities of CH, C2, CN, and OH radicals are determined by highly sensitive absorption spectroscopy. The radical densities are measured as a function of position in the flame for different fuel/oxidant ratios. The growth of diamond is confirmed by scanning electron microscopy and Raman spectroscopy. Of the four radicals measured, the C2 and CH densities are the most correlated with diamond growth. The measured densities are compared with numerical flame models. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 9111-9119 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The gas phase densities of atomic carbon, atomic hydrogen, and methyl radicals are measured in a hot filament diamond deposition system by the use of absorption spectroscopy in the vacuum ultraviolet. The ratio of atomic to molecular hydrogen is also determined using the measured C and CH3 densities and the equilibrium constant for the hydrogen abstraction and recombination reactions that link the C and CH3 densities. The flux of C to the diamond surface is inadequate to explain the total growth rate, though C could have an important role in initiating growth. A model indicates that the hydrogen is dissociated at the filament and diffuses quickly throughout the rest of the system; gas phase reactions only have a small effect on the degree of dissociation. An increased input CH4 mole fraction results in lower hydrogen dissociation by poisoning the catalytic properties of the filament. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5340-5343 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline solid solutions of Ag3SI1−xBrx were prepared from the melt and characterized in the superionic β phase by x-ray diffraction and electrical conductivity. Alloy lattice parameters decrease linearly from x=0.0 to x=1.0 within experimental uncertainty. Room-temperature conductivity of Ag3SI is enhanced with the substitution of bromide for iodide while a corresponding, though smaller, effect is observed in Ag3SBr as iodide is substituted for bromide. The transition temperature separating the superionic β phase and the covalent γ phase in these alloys attains a minimum at x=0.80.
    Type of Medium: Electronic Resource
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