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  • 1
    Electronic Resource
    Electronic Resource
    Molecular bonding in SF6 measured by elastic electron scattering (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 8197-8200 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Elastic differential cross-section measurements of gaseous SF6 were made with 30 keV electrons in the range of 0.25 bohrs−1≤s≤10 bohrs−1. Structural parameters derived in this study closely matched those found in an earlier total (elastic plus inelastic) scattering investigation. Multiple-scattering effects were incorporated in the structural refinement. The discrepancies between the independent atom model and the measured differential cross section reproduce earlier total scattering results for momentum transfers of greater than 5 bohrs−1. By extending the measurements to smaller s values, a closer examination of a Hartree–Fock calculation for SF6 was possible. It was found that the difference curve obtained from the Hartree–Fock calculation matched the experimental data in this region. A more quantitative analysis was performed using the analytic expressions of Bonham and Fink to compute moments of the molecular charge distribution from the differential cross-section data. Comparison of these results with similar fits to the Hartree–Fock calculation confirmed the good agreement between the Hartree–Fock calculation and the current elastic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463442
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  • 2
    Electronic Resource
    Electronic Resource
    An electron diffraction study of alkali iodide vapors (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6053-6057 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structures of NaI, KI, RbI, and CsI in the vapor phase were determined via standard electron diffraction counting techniques with nozzle temperatures ranging from 770–866 K. The data analysis yielded the structure parameters and the ratio of the monomeric to dimeric compounds. The mean amplitudes of vibration for the monomeric molecules were held at values based on microwave frequencies and the harmonic potential approximations. The corrected monomer distances re agree well with microwave-spectroscopy results. Rhombic geometries with bonded dimer distances ranging from 3.00 to 3.57 A(ring) and I–M–I angles that ranged from 95° to 102° were observed. The dimer mole fraction in the vapor varied from 3% to 18%. There was no significant amount of any trimeric species observed in the vapor. The bonded distance of KI was found to be equal to the interionic separation of the crystal. The observed dimer mole fractions were compared with various theoretical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455419
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  • 3
    Electronic Resource
    Electronic Resource
    An electron diffraction study of alkali fluoride vapors (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6058-6063 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structures of NaF, KF, RbF, and CsF in the vapor phase were determined via standard electron diffraction counting techniques with nozzle temperatures ranging from 798 to 1123 K. The reactivity of the fluorides combined with the higher temperature requirements necessitated a new nozzle design as well as modification to the oven. The data analysis yielded the structure parameters and the ratio of monomeric to dimeric compounds. The mean amplitudes of vibration of the monomeric molecules were held at values based on microwave frequencies and the harmonic potential approximation. The corrected monomer distances re agree well with microwave-spectroscopy results. Rhombic geometries with bonded dimer distances ranging from 2.08 to 2.70 A(ring) were observed. The F–M–F bond angles were found to be nearly constant, varying only from 82.2° to 85.5°. The dimer mole fractions in the vapor were observed to vary from 5% to 18%. There were no significant amounts of any trimeric species observed in the vapor. The observed dimer mole fractions were compared with existing measurements from velocity selection experiments and found to be in excellent agreement. The dimer mole fractions were also compared with various theoretical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455420
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  • 4
    Electronic Resource
    Electronic Resource
    Structure of zinc phthalocyanine by gas phase electron diffraction (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 6416-6420 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Gas phase electron diffraction data have been successfully recorded for zinc phthalocyanine. Molecular structure parameters have been determined by least square fitting a geometrically consistent model of C4v symmetry to the data. The results agree well with previous x-ray diffraction studies of crystals. However, the zinc atom was found to be slightly out the plane of the molecule in contrast with the x-ray results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465880
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  • 5
    Electronic Resource
    Electronic Resource
    Vortex dynamics investigation using an acoustic technique (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 3380-3389 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new acoustic technique using the double time-reversal mirrors system and based on geometrical acoustics, is used to study a vortical flow. The interaction between the sound and a vortex is described in details. This technique has been applied to the study of a stretched vortex. This vortex is generated by stretching the vorticity of a boundary layer in a low velocity water channel. It is shown that the velocity field can be reconstructed from the phase distortion of an ultrasonic wave. The technique gives access to a complete characterization of the vortex dynamics, such as the temporal evolution of its size, its circulation and its position. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870197
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  • 6
    Electronic Resource
    Electronic Resource
    A high-temperature pulsed supersonic nozzle (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 3020-3021 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A pulsed supersonic nozzle is presented which can be heated to 1300 K and cooled to 4 K. The whole system is composed of quartz to prevent the decomposition of the molecules at a high temperature. The nozzle has produced gas pulses at a rate of 10 Hz and pulse lengths of 5 ms. The performance of the system is demonstrated by the flight time and the rotational temperature of NO molecules as a function of the stagnation pressure and the nozzle temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144351
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  • 7
    Electronic Resource
    Electronic Resource
    New vapor phase spontaneous Raman spectrometer (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3280-3284 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A highly sensitive, spontaneous Raman spectrometer designed for the study of vapors and other low-density samples is discussed. The high sensitivity is achieved by means of the novel combination of a multipass light cell and a high-temperature gasdynamic focusing system. A complete description of the apparatus is given, along with the results of a sensitivity test in ambient air, as well as results demonstrating gasdynamic focusing of a vapor and Raman transitions in such a sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142537
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  • 8
    Electronic Resource
    Electronic Resource
    A pulsed supersonic molecular beam with high rotational temperatures (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 407-411 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The construction and operation of a novel high temperature pulsed quartz nozzle employed for the generation of rotationally excited supersonic molecular beams are reported herein. At high stagnation pressures ((approximately-greater-than) 1 bar) the NO molecules in the beam pulse exhibit a translational and rotational behavior identical to heated continuous nozzles (Trot〈50 K; Ekin≈7/2 kTN). At reduced stagnation pressures (10 mbar–1 bar) the rotational temperatures of the beam molecules are increased substantially (up to Trot≈700 K) accompanied by a translational behavior, which can be characterized by a small Mach number. The design has produced the rotationally hottest supersonic beam ever prepared in the pulsed mode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145147
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  • 9
    Electronic Resource
    Electronic Resource
    Optical probing of pulsed, focused ultrasonic fields using a heterodyne interferometer (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 153-155 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The pulsed acoustic field of a piezoelectric focused transducer transmitted in water has been investigated by using an optical heterodyne interferometer. The probe beam is reflected by a thin membrane that follows the motion of the fluid particle. Absolute measurements of the mechanical displacement have been performed in the frequency range 5–15 MHz with a spatial resolution better than 0.1 mm and a sensitivity of 0.1 nm with a 20 MHz detection bandwidth that corresponds to a minimum detectable acoustic energy density of 2 μJ/m2. The experimental results all agree quantitatively with diffraction theory predictions of impulse response at the focus of the transducer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108202
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  • 10
    Electronic Resource
    Electronic Resource
    Transient elastic wave generation by an array of thermoelastic sources (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3276-3278 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A set of 16 thermoelastic strip sources, equivalent to a phased array of ultrasonic transducers has been implemented on a solid by irradiating its surface with a multiple beam pulsed YAG laser. Longitudinal elastic waves were focused in the sample by time delaying each laser pulse. Results of experiments performed on duraluminum in the thermoelastic regime are presented and compared with simulations based on the surface center of the expansion model. It is shown that with this technique, a high energy focusing, together with an ultrasonic beam scanning can be achieved in a wide angular range leading to a significant improvement in the signal-to-noise ratio of a laser based ultrasonic system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110173
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