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  • 1
    Electronic Resource
    Electronic Resource
    The vibrational spectrum and rotational constants of difluoroethyne FC 3/4 CF. Matrix and high resolution infrared studies and ab initio calculations (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5660-5669 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared spectra of the short-lived difluoroethyne molecule have been recorded in neon and argon matrices between 200 and 5000 cm−1. Fourier transform infrared spectra with a resolution of 0.004 cm−1 have been measured in the gas phase around 1350 cm−1 (ν3, ν2+ν4+ν5, hot bands) and 2150 cm−1 (ν2+ν3, ν1−ν5, hot bands). The high resolution study yields rotational parameters of the ground and all singly excited vibrational states. The interpretation of the experimental data has been guided by ab initio calculations at the SCF (self-consistent-field) level and the correlated MP2 level (Moller–Plesset second order perturbation theory) employing three different large basis sets. The theoretical calculations provide the SCF and MP2 harmonic fields as well as the SCF anharmonic force field of FCCF. The agreement between the available theoretical and experimental results is generally quite good, with the exception of the spectroscopic constants involving the trans-bending mode ν4 where more theoretical work is required. The combined use of theoretical and experimental information leads to an estimate of the equilibrium structure [D∞h, re(CC)=1.1865 A(ring), re(CF)=1.2832 A(ring)] and to recommended "best'' values for the wave numbers of all fundamental vibrations based on the matrix and high resolution infrared data and some ab initio anharmonicity constants. The present study demonstrates the advantages of a combined theoretical and experimental approach to the spectroscopy of short-lived molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461640
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  • 2
    Electronic Resource
    Electronic Resource
    High-resolution rotation–vibration spectroscopy of difluorophosphorane: A combined theoretical and experimental study (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4603-4614 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The harmonic and anharmonic force fields of PH3F2 have been calculated at the ab initio self-consistent-field level using polarized split-valence and triple-zeta basis sets. PH3F2 has been prepared in pure form and identified unambiguously in the gas phase by Doppler-limited Fourier transform infrared spectroscopy. Guided by the theoretical predictions for the rotation–vibration spectra and the spectroscopic constants, the observed bands have been assigned and several of them rotationally analyzed, in particular ν4/2ν±27, ν2+ν4/ν2+2ν±27, and ν5/ν3+ν8. PH3F2 is found to have a D3h structure, ro(PH)=1.394(4) A(ring) and ro(PF)=1.6468(2) A(ring). The theoretical results are in good agreement with experiment, both for the structure and for the available spectroscopic constants. The present study demonstrates the advantages of a combined theoretical and experimental approach to the spectroscopy of reactive molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458700
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  • 3
    Electronic Resource
    Electronic Resource
    Fractional diffusion and wave equations (1989)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 30 (1989), S. 134-144 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Diffusion and wave equations together with appropriate initial condition(s) are rewritten as integrodifferential equations with time derivatives replaced by convolution with tα−1/Γ(α), α=1,2, respectively. Fractional diffusion and wave equations are obtained by letting α vary in (0,1) and (1,2), respectively. The corresponding Green's functions are obtained in closed form for arbitrary space dimensions in terms of Fox functions and their properties are exhibited. In particular, it is shown that the Green's function of fractional diffusion is a probability density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.528578
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  • 4
    Electronic Resource
    Electronic Resource
    Chemical reactivity of size-selected supported clusters: An experimental setup (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1986-1994 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe an experimental setup for the investigation of the chemical reactivity of size-selected, supported clusters. The clusters are generated by a high frequency laser vaporization source. After mass selection and energy control the clusters are deposited under ultrahigh-vacuum conditions and with low kinetic energy onto thin oxide films grown on metal single crystals. Such films are ideal in their function as supports for size-selected deposited metal clusters. Measured currents of mass-selected niobium cluster ions were of the order of 1 nA and are high enough for fast deposition rates. Adsorbed molecules used on the one hand as probes to characterize the supported clusters and on the other hand for studying chemical reactions on these clusters are investigated in situ by Fourier transform infrared spectroscopy, temperature desorption spectroscopy, and Auger electron spectroscopy. The performance of these analytical tools is illustrated with CO adsorbed on Ni atoms supported on thin MgO(100) films grown on a Mo(100) single crystal. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148113
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  • 5
    Electronic Resource
    Electronic Resource
    Improvement of q-profile measurement by fast observation of pellet ablation at ASDEX Upgrade (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 4051-4060 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The q-profile measurement presented in this article is based on the observation of pellets injected into the plasma and viewed with a fast-framing camera. The pellets sublimate in the plasma and the ablated material is ionized. The ions move along the magnetic field lines, while an ablation cloud is forming. This ablation cloud contains a small fraction of neutral particles which emit visible light after collisional excitation. It is therefore possible to visualize the magnetic field lines along which the pellet passes. The inclination angle of the magnetic field lines with respect to the torus midplane can be determined from this observation. The results are compared with the inclination angles delivered by an equilibrium code. Further analysis shows that it is not meaningful to determine the q-profile from the data of only the pellet ablation, in the case of an elongated plasma as in ASDEX Upgrade. However, the accuracy of the q-profile determined by an equilibrium code, especially in the plasma center, can be greatly improved by using the pellet measurements as additional input data. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148386
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  • 6
    Electronic Resource
    Electronic Resource
    Apparent superstructures in scanning tunneling microscopy (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 921-923 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Apparent superstructures have been observed with scanning tunneling microscopy (STM) on well-ordered Ag(110) surfaces. These superstructures are due to the discrete sampling of the atomic corrugation in STM. Such sampling effects may explain superstructures observed previously with STM on graphite surfaces. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114695
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  • 7
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    Development of the CD Symcap platform to study gas-shell mix in implosions at the National Ignition Facility (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-09-10
    Description: Surrogate implosions play an important role at the National Ignition Facility (NIF) for isolating aspects of the complex physical processes associated with fully integrated ignition experiments. The newly developed CD Symcap platform has been designed to study gas-shell mix in indirectly driven, pure T 2 -gas filled CH-shell implosions equipped with 4 μ m thick CD layers. This configuration provides a direct nuclear signature of mix as the DT yield (above a characterized D contamination background) is produced by D from the CD layer in the shell, mixing into the T-gas core. The CD layer can be placed at different locations within the CH shell to probe the depth and extent of mix. CD layers placed flush with the gas-shell interface and recessed up to 8  μ m have shown that most of the mix occurs at the inner-shell surface. In addition, time-gated x-ray images of the hotspot show large brightly radiating objects traversing through the hotspot around bang-time, which are likely chunks of CH/CD plastic. This platform is a powerful new capability at the NIF for understanding mix, one of the key performance issues for ignition experiments.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 8
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    A uniformly valid solution for the hypersonic flow past blunted bodies (1968)
    Cambridge University Press
    Details
    Publication Date: 1968-01-29
    Description: The plane and axisymmetric hypersonic flow past blunted bodies is investigated as an inverse problem (shock shape given). The fluid may behave as a real gas in local thermodynamic equilibrium. Viscosity and heat conduction are neglected. An analytical solution uniformly valid in the whole flow field (from the stagnation region up to large distances from the body nose) is given. The solution is based on two main assumptions: (i) the density ratio ε across the shock is very small, (ii) the pressure at a pointPof the disturbed flow field isnotvery small compared with the pressure immediately behind the shock in the intersection point of the shock surface with its normal throughP.TermsO(ε) are neglected in comparison with 1, but it is not necessary for the shock layer to be thin. The change of velocity along streamlines is taken into account. In order to calculate the flow quantities one has to evaluate only two integrals (equations (49) and (53) together with the boundary values (5) and (10)). The application of the solution is illustrated and the accuracy is tested in some examples.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 9
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    Kinematic-wave theory of sedimentation beneath inclined walls (1982)
    Cambridge University Press
    Details
    Publication Date: 1982-07-01
    Description: The two-phase flow in settling vessels with walls that are inclined to the vertical is investigated. By neglecting inertial effects and the viscosity of the suspension it is shown that the particle concentration remains constant on kinematic-wave fronts. The wave fronts are horizontal and propagate in a quasi-one-dimensional manner, but are imbedded in a two-dimensional or three-dimensional basic flow which, in turn, depends on the waves via the boundary conditions. Concentration discontinuities (interfaces) are described by kinematic-shock theory. The kinematic shocks are shown to be horizontal, with the possible exception of discontinuities that separate the suspension from the sediment. At downward-facing inclined walls conservation of mass enforces the existence of a boundary-layer flow with relatively large velocity. As G/R2→∞ and G/R4→0, where G and R are respectively a sedimentation Grashof number and a sedimentation Reynolds number, the entrainment of suspended particles into the boundary-layer flow of clear liquid is negligibly small. This provides an appropriate boundary condition for the basic flow of the suspension. Thus, in the double limit considered, a kinematic theory suffices to determine the convective flow of the suspension due to the presence of inclined walls. As an example batch sedimentation in vessels with inclined plane or conical walls is investigated. The settling process is terminated after a time that can be considerably smaller than the time required in a vertical vessel under the same conditions. Depending on the initial particle concentration, there are centred kinematic waves that are linked to a continuous increase of the particle concentration in the suspension. In an appendix, the flow in the boundary layer at a downward facing, inclined wall is investigated. With G/R2→∞ and G/R→0 the boundary layer consists of an inviseid particle-free main part, a viscous sublayer at the wall, and a free shear sublayer at the liquid/particle interface. © 1982, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 10
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    Flow induced by jets and plumes (1981)
    Cambridge University Press
    Details
    Publication Date: 1981-07-01
    Description: The order of magnitude of the flow velocity due to the entrainment into an axisymmetric, laminar or turbulent jet and an axisymmetric laminar plume, respectively, indicates that viscosity and non-slip of the fluid at solid walls are essential effects even for large Reynolds numbers of the jet or plume. An exact similarity solution of the Navier-Stokes equations is determined such that both the non-slip condition at circular—conical walls (including a plane wall) and the entrainment condition at the jet (or plume) axis are satisfied. A uniformly valid solution for large Reynolds numbers, describing the flow in the laminar jet region as well as in the outer region, is also given. Comparisons show that neither potential flow theory (Taylor 1958) nor viscous flow theories that disregard the non-slip condition (Squire 1952; Morgan 1956) provide correct results if the flow is bounded by solid walls. © 1981, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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