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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1812-1819 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A tunable far-infrared difference frequency spectrometer has been used to examine the fully protonated form of malonaldehyde in the region near the ground-state tunneling frequency (21 cm−1). An extremely dense and complex spectrum is observed in which the strongest features have been assigned as pure rotational lines involving high values of J and K−1. These transitions, which occur within the individual rotational manifolds of the two halves of the ground-state tunneling doublet, have been analyzed simultaneously with existing microwave data for this species. The value of the ground-state tunneling splitting, determinable indirectly from analysis of vibration–rotation interactions, is 21.584 76(17) cm−1, and is in close agreement with that similarly obtained in previous microwave work. A thorough treatment of the centrifugal distortion in this system significantly extends the range of rotational states whose energies may be reliably calculated, and should therefore be valuable in the future direct measurement of the tunneling frequency. Aspects of the far-infrared spectrum of this species, and of the indirect method of determining the tunneling splitting, are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 2413-2421 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The two Σ and four Π states of the weakly bound complex Ar–NH3 correlating to j=2, k=±1 ammonia have been observed by tunable far infrared difference frequency-microwave sideband spectroscopy. The results have been combined with published data to determine a new angular potential energy surface for the system. The barrier to threefold internal rotation of the NH3 about its C3 axis in the complex is estimated to be 25.606(24) cm−1 near the minimum energy (T-shaped) configuration. The potential also exhibits maxima at both symmetric top configurations, with energies approximately 53 and 31 cm−1, respectively above that of the global minimum. The location and splitting between the symmetric and antisymmetric Σ states are indicative of a strong interaction with another pair of unobserved states, most likely the first excited intermolecular stretch built on j=1, k=±1 Ar–NH3.
    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 74 (1993), S. 7521-7530 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reaction products contained in the exhaust gas of a dc plasma jet reactor system were detected using mass spectrometry. The major reaction products formed from a feed gas mixture of 96% H2, 3% CH4, and 1% O2 injected into an argon plasma jet were CH4, C2H2, C2H6, CO, and H2O. The products formed without O2 in the reactor feed were CH4, C2H2, and C2H6. Addition of O2 to the reactor gas feed increased the diamond deposition rate by ∼30% with no degradation in quality. A chemical kinetics model for flames was adapted to this reactor and accurately predicted the major reaction products formed for a reactor feed without O2, indicating the gas phase chemistry may be described by a reaction set developed for hydrocarbon combustion and the chemistry is thermally driven. When compared to experimental results, the model predicts: (1) a maximum temperature in the gas of 3000 K, (2) only 1.2% of the H2 in the reactor feed is dissociated, and (3) CH3 is the primary diamond growth precursor.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2487-2489 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A significant enhancement in the quality of diamond films grown using a remote CH4 carbon source was observed in a direct current arcjet chemical vapor deposition reactor. The linewidths of the diamond peak at 1332 cm−1 in the Raman spectra from these films were reduced from 9.0 to 6.5 cm−1 with no reduction in mass deposition rate as compared to films grown using premixed reactor gas feeds. For diamond growth conditions, the percentage of the reactor feed carbon reaching the substrate was measured to be ∼35%. The enhanced quality of the films is attributed to reduced residence times of the carbon source in the plasma, which would limit the gas phase chemistry from proceeding beyond CH3 formation before the gas reaches the substrate.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 10630-10637 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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