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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7997-7999 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The double resonance technique has been applied to a molecular ion. We have observed microwave-infrared double resonance signals of HN+2 produced in a hollow cathode discharge at low pressures (20–200 mTorr). A color center laser with 2–20 mWatts of power provided the infrared signal radiation, and a millimeter wave klystron with ∼400 mWatts of power provided the microwave pump radiation. The frequency of the microwave radiation was swept and the double resonance signal was detected through variation of the infrared power. Using the R(1) and P(1)infrared transitions we have observed the J=1←0 rotational transition in both the ground state and the ν1 state. We have observed not only the direct three-level double resonance signals, but also collision-induced four-level double resonance signals indicating the existence of some selection rules for the Langevin potential dominated ion–neutral interaction. The major results of this paper are: (1) The double resonance method is now applicable to molecular ions and (2) ion–molecule collisions have selection rules.
    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 93 (1990), S. 87-93 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared–microwave double resonance spectroscopy has been used to study the simple molecular ion HN+2. This is the first application of this powerful method to a molecular ion. The HN+2 ion was produced in a hollow cathode discharge cell, which served two purposes. First, the hollow cathode discharge is capable of producing relatively large concentrations of ions at the low pressures required for saturation. Also, the hollow cathode serves as a waveguide for the propagation of the microwave radiation. A color center laser was used as the infrared source. Its high power was essential in this work for saturation of the infrared transitions. The HN+2 ion was chosen as a test case for double resonance because of the availability of detailed spectroscopic information and its ease of production. We have observed the pure rotational transition J=1←0 in both the ground and ν1 states using the ν1 infrared fundamental. The determined molecular constants are eqQ=−5.88(10) MHz and B=46 586.895(18) MHz for the ground state, and eqQ=−5.71(17) MHz and B=46 208.986(27) MHz for the ν1 state. The high sensitivity of the double resonance technique has also allowed us to study the direct l-type doubling transitions in the ν2 and ν1+ν2 states using the ν1+ν2←ν2 infrared hot band. To the best of our knowledge, this is the first centimeter wave spectrum of a molecular ion. The determined molecular constants are q=254.966(11) MHz and qJ =−2.83(17) kHz for the ν2 state, and q=258.912(32) MHz and qJ =−3.15(65) kHz for the ν1+ν2 state.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 8725-8735 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A high resolution spectroscopic study of HI+ has been carried out for the first time. The absorption spectrum in the inverted 2Π ground electronic state has been measured with a linewidth of 0.004 cm−1 between 1995 and 2245 cm−1. A total of 117 vibration–rotation transitions were observed with a tunable diode laser spectrometer coupled to an ac glow discharge cell employing velocity modulation. Lines were measured in the vibrational fundamental of the 2Π1/2 spin substate and in the three lowest (v+1←v) bands of the 2Π3/2 spin substate. A good fit to the data was obtained using a standard vibration–rotation, fine structure Hamiltonian. Equilibrium values were determined for 16 molecular parameters including the harmonic vibrational frequency ωe, the rotational constant Be, and the Λ-doubling constants pe and qe. A review of the ground state properties of the hydrogen halide ions HX+ (X=F, Cl, Br, I) shows that the harmonic force constant is, to excellent approximation, a linear function of the internuclear spacing. In ten different vibration–rotation transitions of the two spin substates of HI+, hyperfine splittings were observed. A total of 58 relative splittings of hyperfine components were analyzed to determine the iodine quadrupole coupling constant eQq0 as well as the Frosch–Foley magnetic hyperfine constants a, (b+c), and d. The results have been used to investigate the electronic properties of the ion. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 5977-5987 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A color center laser spectrometer along with velocity modulation detection was used to record the absorption spectrum of H2O+ produced in an AC glow discharge between 3180 and 3390 cm−1 with a gas mixture of He/H2O. The predominant role of the reaction of metastable helium with H2O has been observed. The H2O+ ion is also present in the spectra recorded between 3100 and 3600 cm−1 with a gas mixture of He/H2/O2 and some features are illustrated. The ν1 and ν2+ν3−ν2 bands have been assigned and the previous analysis of the ν3 band [J. Mol. Spectrosc. 127, 1 (1988)] has been extended. The ν1 and ν3 states have been fitted together taking into account the vibration–rotation interaction. The molecular constants have been obtained for the ν1 and ν2+ν3 states and they have been improved in the case of the ν3 and the ground vibrational states. The equilibrium structure has been derived [re=0.9992(6) A(ring), θe=109.30(10)°] and the quadratic and cubic force field constants have been evaluated.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Molecular Spectroscopy 123 (1987), S. 251-253 
    ISSN: 0022-2852
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 145 (1988), S. 153-159 
    ISSN: 1615-6102
    Keywords: Golgi apparatus ; Microtubules ; Video-enhanced fluorescence microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Communications in Applied Numerical Methods 5 (1989), S. 253-261 
    ISSN: 0748-8025
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The relative performances of five pressure-velocity coupling solution algorithms, SIMPLE, CTS SIMPLE, SIMPLER. SIMPLEC and FIMOSE, are evaluated for three turbulent flow problems. The characteristics of these methods are investigated based on the computational effort required to reach certain levels of residuals in mass, momentum and turbulent kinetic energy. Comparisons of these methods used to solve turbulent flows in the present study and laminar calculations in previous literature are made to reveal the characteristic behaviour of these algorithms in the computation of these two flow regimes. It is found that SIMPLEC is the most efficient and stable method for solving the complex turbulent flows and its performance is not always identical to CTS SIMPLE. SIMPLER needs the fewest iterations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Communications in Applied Numerical Methods 5 (1989), S. 99-104 
    ISSN: 0748-8025
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A modified model based on the turbulent kinetic energy equation is used to predict the recirculating swirling flowfield. The model properly includes the wave and oscillation nature of the swirling flow and redefines the energy budget in the turbulent kinetic energy equation. This brings about significant improvements in the recirculation zone as well as the recovery region, as compared with the results from models used by Rodi and Launder et al. of the Richardson number type corrections in the dissipation equation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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