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  • 11
    Electronic Resource
    Electronic Resource
    Spectroscopic characterization of mesogen order in discotic liquid crystal (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5950-5955 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared and Raman spectra of the discotic liquid crystal molecules benzene–hexa-hexanoate (BH6), benzene–hexa-heptanoate (BH7), benzene–hexa-octanoate (BH8), and benzene–hexa-nananoate (BH9), and of mixtures of BH7 with BH8, are reported as a function of temperature. The 1615 cm−1 infrared band is strong in the Raman spectrum of BH7 and is taken as a characteristic of and diagnostic for central core disorder in all these molecules and mixtures. The aliphatic side chains are shown to disorder at much lower temperatures than the central core, and order in the central core is shown to remain throughout the liquid crystalline region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455546
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  • 12
    Electronic Resource
    Electronic Resource
    Efficient state-specific preparation of highly vibrationally excited NO(X 2Π) (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 116-120 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational levels of nitric oxide (NO) X 2Π from v‘=8–24, whose energies vary from 1.76 to 4.61 eV, have been produced using the stimulated emission pumping (SEP) technique. A narrowband tunable argon fluoride laser is used to access the B 2Π state which provides good Franck–Condon overlap with many vibrational levels of the ground electronic state. Saturation of the transitions is achieved at low pulse energies providing high pumping efficiency. Both spin–orbit states of NO are accessible with this scheme. Accurate molecular constants for v‘=23 and 24 are given for the first time. The feasibility of an optically pumped infrared laser is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458480
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  • 13
    Electronic Resource
    Electronic Resource
    A study of the structure and dynamics of the hydronium ion by high resolution infrared laser spectroscopy. III. The ν3 band of D3O+ (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 3257-3260 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: 294 transitions were measured by velocity modulation spectroscopy using a difference frequency laser system with a D2/O2 discharge and assigned to the ν3 (antisymmetric stretch) band of D3O+. A simultaneous analysis of this data with the ν2 band spectra reported by Sears, et al. [J. Chem. Phys. 83, 2676 (1985)] yielded a refined set of parameters for both the ground and the excited states of both bands. The ν3 bandcenters are 2629.6512(39) and 2624.2376(47) cm−1 for the s–s and a–a inversion components, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457884
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  • 14
    Electronic Resource
    Electronic Resource
    Mössbauer study on the coupling interaction of Fe-based nanocrystalline alloys (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5124-5126 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A two-phase system of Fe-based nanocrystalline alloys is here investigated. The nanocrystalline Fe69.5Cu0.5Cr4V5Si13B8 alloys, which consist of two magnetic phases: α-FeSi grains and an amorphous matrix, were prepared by annealing the amorphous ribbons. Mössbauer spectroscopy and magnetic measurements at elevated temperatures were carried out. The results show that the exchange coupling interaction exists between grains through the amorphous matrix, and obviously affect the soft magnetic properties of the nanocrystalline alloys. A phenomenological coupling model is applied to estimate the coupling intensity for samples annealed at different temperatures and the data can reasonably explain why the nanocrystalline alloys annealed at 540 °C hold the best soft magnetic properties. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369098
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  • 15
    Electronic Resource
    Electronic Resource
    Temperature and cluster size dependence studies of reactions of protonated water clusters with acetonitrile (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 130-134 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The temperature dependence of reactions of protonated water clusters H+(H2O)n with acetonitrile CH3CN was studied in a fast-flow reactor over the temperature range of 300–130 K and for cluster sizes from n equals 1 to 22. The measured rate constants were found to agree well with the calculated values based on a parametrized trajectory method [T. Su and W. J. Chesnavich, J. Chem. Phys. 76, 5183 (1982); over the entire range of the temperatures and cluster sizes studied. The rate constants measured in this work also agree very well with other reported values at room temperature. These results demonstrate that collisional rate constants for the type of the cluster-ion–molecules reactions studied here can be calculated accurately by the theoretical method at room as well as low temperatures. This conclusion not only has a direct bearing on other research fields, e.g., the modeling atmospheric ion chemistry at low temperatures, but also offers insight into the reaction dynamics of cluster-ion–molecule reactions as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461468
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  • 16
    Electronic Resource
    Electronic Resource
    The potential energy function for O2 X(3∑−g ) and the transition dipole moment of the Schumann–Runge band near X-state dissociation (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7114-7117 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Emission spectra were analyzed for transitions of O2 (B 3∑−u, v'→X 3∑−g, v‘) with v‘ as high as 35. The X 3∑−g potential energy function, Vx (r), was determined nearly to the dissociation limit with an estimated accuracy of ±50 cm−1. Vx (r) is compared to the highest level ab initio calculation available. The transition dipole moment function, μ(r), for the O2 Schumann–Runge band is also extended almost to the dissociation limit. The O2 molecule now provides one of the best testing grounds for ab initio theories of dissociation and radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456240
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  • 17
    Electronic Resource
    Electronic Resource
    Broadband density fluctuation measurements using a heavy ion beam probe on the Texas Experimental Tokamak (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3360-3367 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Broad bandwidth (60 kHz ≤f≤500 kHz), long wavelength (k¯θ≤2 cm−1) density fluctuation measurements were made using a heavy ion beam probe on the Texas Experimental Tokamak (TEXT) [K. W. Gentle, Nucl. Technol./Fusion 1, 479 (1981)]. Fluctuation amplitudes and correlation length scalings do not correspond to linear or quasilinear drift wave theory. Power-weighted root-mean-square (rms) wave number estimates are much lower (〈k¯θ〉rmsρs≤0.1, ρs=[miTe]1/2/eB) than quasilinear theoretical expectations (k¯⊥ρs∼0.3). Core results indicate strong turbulence with a wave number spread, Δk∼k¯ at fixed frequency f, consistent with strong turbulence predictions, while edge results can be considered consistent with weak turbulence. In between the core and edge (0.6≤r/a≤0.8) is a transition region. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871170
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  • 18
    Electronic Resource
    Electronic Resource
    Broadband fluctuation wave number measurement technique using a heavy ion beam probe : Eighth topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3058-3060 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The heavy ion beam probe (HIBP) measures localized density fluctuations in the plasma interior. These measurements can be used to calculate two point estimates of interior poloidal wave numbers. The results so far show wave numbers significantly lower than FIR scattering wave numbers and drift wave expectations. Experiments were performed on TEXT to look for possible sources of error in our wave number calculations. The HIBP effects that are considered the possible dominant error terms are finite sample volume size and path effect fluctuations as well as the possible existence of counter-propagating modes. An aperture experiment showed the presence of a finite sample volume effect, but not large enough to correct the measured wave numbers significantly. Simulations using HIBP data show that our processing techniques detect counter-propagating modes. Path effects are discussed. The error analysis so far shows the HIBP calculations to be accurate wave number measurements, but more study on path effects is needed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141726
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  • 19
    Electronic Resource
    Electronic Resource
    MHD magnetic fluctuation measurements using a heavy ion beam probe : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3061-3063 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes a technique for measuring magnetic fluctuations using a heavy ion beam probe (HIBP) and presents the results of the first experiment to measure locally the internal magnetic structure of MHD modes in a hot, tokamak plasma. In these experiments on the TEXT tokamak, the toroidal position of the HIBP beam at the detector is used to measure the toroidal component of the magnetic vector potential fluctuations, A˜φ, at a localized position in the plasma. In an axisymmetric system a purely local measurement is possible. However, the detection method employed and the asymmetries in the tokamak introduce path effects. The importance of the path effects is estimated through numerical simulations of the experiment, and it is found that in this experiment the path effects are small throughout much of the plasma. In addition, toroidal asymmetries reduce the signal amplitude, but do not greatly distort the radial profile. The accuracy of the numerical simulations and detection technique is tested in a plasma with a known A˜φ, with agreement obtained to within 5%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141727
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  • 20
    Electronic Resource
    Electronic Resource
    Intramolecular coupling enhanced predissociation in HCCCN–HCN (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 2727-2734 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effect of intramolecular couplings on the dynamics of predissociation in the HCCCN–HCN complex has been studied using optothermal high resolution IR spectroscopy. Two perturbations have been observed in the ν2 band. In both cases, predissociation is enhanced by the perturbations. Because of the particular values of the rotational level spacing and the unperturbed linewidth (lifetime) of this band, perturbations are seen to affect several levels as the perturbing states tune in and out of resonance with the infrared active state. An analysis of the line intensities indicates that one of the perturbations is anharmonic in nature. A simple Fermi's golden rule two level model for the perturbation around J=10 of the v2=1 state (the one measured with better signal to noise ratio) can not explain the experimental linewidths. Other models involving more than two levels are discussed, but firm interpretation of the data must await for a more complete theoretical analysis which goes beyond the scope of this article.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464154
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