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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical and experimental investigation of the reaction BH+D2→BHD2 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 479-488 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rate of the association reaction, BH+D2→BHD2 is determined both theoretically and experimentally. In the theoretical calculations, potential-energy surface information is obtained using multiconfiguration self-consistent-field and large-scale multireference configuration-interaction calculations with large correlation consistent basis sets. The preferred direction of approach is found to be along a non-least-motion pathway for which the BH and DD bonds come in nearly parallel to one another. The small computed activation energy of 2.6 kcal/mol for this highly exothermic reaction is found to arise almost exclusively from changes in zero-point vibrational energy. The experimental measurements of the BH disappearance rate are made at temperatures from 298 to 597 K and are shown to be only weakly dependent on total pressure over the range of 1–100 Torr. As a test of the proposed mechanism, we observe the growth of BD and find the BD appearance rate constant to be in excellent agreement with that for BH disappearance. The measured reaction rates are compared to the results of canonical variational transition-state theory calculations of the association rate and are found to be in excellent agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459547
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  • 2
    Electronic Resource
    Electronic Resource
    Photoabsorption and direct dissociation cross sections of C2H2 in the 1530–1930 A(ring) region: A temperature dependent study (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 272-280 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using synchrotron radiation as a continuum light source, the absolute photoabsorption and direct dissociation cross sections of C2 H2 in the 1530–1930 A(ring) region have been measured at 295 and 155 K. In comparison with cross sections obtained at room temperature, the cross sections at absorption peaks typically increase by 10%–40% while those at absorption valleys decrease by as much as 30% at 155 K. Further, the absorption band profiles become narrower as the gas temperature decreases. In the presently studied wavelength region, there are at least three electronic states, namely, the A˜ 1 Au , the B˜ 1 Bu , and a continuum. Using the present low temperature data we have constructed the repulsive potential energy curve of the direct dissociation state according to the Franck–Condon principle. The potential energy curve thus constructed can be more accurate than that constructed by using room temperature cross section data because only the absorption cross section from the ν'=0 level contributes. The present cross section data have also been used in the analysis of oscillator strength distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457513
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  • 3
    Electronic Resource
    Electronic Resource
    Doppler-free polarization spectroscopy of the B 1Πu –X 1Σ+g band system of K2 (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 45-53 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The B 1Πu–X 1Σ+g band system of the K2 molecule is investigated by Doppler-free polarization spectroscopy in a heat pipe oven. The transitions are measured in the region of 615 to 660 nm including vibrational levels up to v″=17 in the X state and all vibrational levels of the B state up to the dissociation limit. A Fabry–Perot interferometer is calibrated using metastable neon and K2 secondary wavelength standards to provide absolute accuracy in the frequency determination of less than 20 MHz. The comprehensive study of the band system is completed by LIF measurements to determine vibrational levels of the ground state up to v‘=62. A detailed analysis has been completed and the coefficients are given in a Dunham expansion that accurately represents the frequencies of lines with specified vibrational and rotational quantum numbers. The B and X potential curves and the Franck–Condon factors for the transitions between B and X states are determined. The dissociation energies have been found to be 4447±15 cm−1 for the X state and 2113±15 cm−1 for the B state. The height of the potential barrier of the B state above the 4 2P3/2+4 2S1/2 atomic levels is 295±17 cm−1 at an internuclear distance of 8.1±0.1 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453591
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  • 4
    Electronic Resource
    Electronic Resource
    Device for measuring sound speeds in reactive liquids at high pressure and temperature (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1402-1408 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have designed a device for measuring sound speeds in reactive liquids at high pressure and temperature. It has been tested in experiments on liquid-potassium metal at pressures up to 0.7 GPa and temperatures up to 423 K. The limitations on pressure and temperature were imposed by auxiliary instrumentation rather than the properties of the device, and it seems likely that it would be suitable for more extreme conditions. The data on potassium agree well with precise room-temperature data. The sound velocities measured as a function of pressure at various temperatures can be used to calculate equation-of-state parameters such as the bulk modulus and its pressure derivatives. The experiments on potassium indicate that bulk modulus can be determined to ±1%, its first pressure derivative to about ±5%, and second pressure derivative to about ±50% (the last for a run with a 0.7-GPa pressure range). The device should permit sound velocity measurements in a variety of liquids which are reactive, corrosive, and/or miscible with pressure media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138493
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  • 5
    Electronic Resource
    Electronic Resource
    Shock structuring due to fabrication joints in targets (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 3327-3336 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of copper-doped beryllium ablators on National Ignition Facility [J. A. Paisner et al., Laser Focus World 30, 75 (1994)] targets, in place of plastic, can require the bonding together of hemispheres with a joint of differing composition. Indirect drive experiments have been conducted on the Nova laser [J. L. Emmet, W. F. Krupke, and J. B. Trenholme, Sov. J. Quantum Electron. 13, 1 (1983)], and the resulting shock structuring compared with code simulations. It is concluded that one of the available codes, the RAGE code [R. M. Baltrusaitis et al., Phys. Fluids 8, 2471 (1996)] provides useful insight into the effect of joints. This code is then employed to obtain a physical picture of the shock front nonuniformity in terms of a secondary rarefaction and an oblique shock interacting with the main shock that propagates in the absence of the joint. A simple analysis reinforces this picture.© 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873572
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  • 6
    Electronic Resource
    Electronic Resource
    Production of enhanced pressure regions due to inhomogeneities in inertial confinement fusion targets : The 41st annual meeting of the division of plasma physics of the american physical society (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 2007-2013 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that regions of enhanced pressure have been produced in targets with indirect radiation drive in planar and cylindrically convergent geometry through the interaction between the flows caused by target inhomogeneities and the main target drive. Design calculations for National Ignition Facility (NIF) [J. A. Paisner et al., Laser Focus World 30, 75 (1994)] targets with beryllium ablators formed by bonded hemi-shells [D. C. Wilson et al., Bull. Am. Phys. Soc. 43, 1667 (1998)] indicate that related behavior produces a seed perturbation in the ablator which can in some cases lead to the suppression of ignition. From simulation and analysis of the NIF problem in the planar geometry analog, a scaling for the perturbation, which should be useful for validation of the behavior with lower energy drive and smaller-scale geometries, is derived. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874022
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  • 7
    Electronic Resource
    Electronic Resource
    Investigation of charge storage in InAs/AlAsSb quantum well capacitors (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1118-1120 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the electrical chracterization of an InAs/AlAsSb quantum well heterostructure capacitor fabricated on material grown by molecular beam epitaxy. Hysteresis associated with electron storage was observed in the capacitance-voltage data from which we derived exponential charge decay constants of 50 s at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101675
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  • 8
    Electronic Resource
    Electronic Resource
    Meeting the challenge of detecting ion plasma waves (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2207-2215 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion plasma waves—purely electrostatic ion waves with a wavelength of order of the electron Debye length and frequency of the order of the ion plasma frequency—have long been known in theory but have proven difficult to detect experimentally. The difficulties stemmed from the techniques used to produce the plasma and to drive and detect the waves. In the work reported here, these problems were overcome by using resonant laser scattering to detect ion plasma waves in a multiply ionized, laser-produced plasma. This nonetheless required careful experimental design to minimize frequency smearing of the scattered signal by plasma gradients. The plasma was extensively characterized, allowing comparison of the theoretical dispersion relation with the wave data. The agreement of these two provides conclusive proof of the detection of ion plasma waves. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871243
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  • 9
    Electronic Resource
    Electronic Resource
    The development and advantages of beryllium capsules for the National Ignition Facility : The 39th annual meeting of division of plasma physics of APS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1953-1959 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Capsules with beryllium ablators have long been considered as alternatives to plastic for the National Ignition Facility laser [J. A. Paisner et al., Laser Focus World 30, 75 (1994)]; now the superior performance of beryllium is becoming well substantiated. Beryllium capsules have the advantages of high density, low opacity, high tensile strength, and high thermal conductivity. Three-dimensional (3-D) calculations with the HYDRA code [NTIS Document No. DE-96004569 (M. M. Marinak et al. in UCRL-LR-105821-95-3)] confirm two-dimensional (2-D) LASNEX [G. B. Zimmerman and W. L. Kruer, Comments Plasmas Phys. Controlled Thermonucl. Fusion 2, 51 (1975)] results that particular beryllium capsule designs are several times less sensitive than the CH point design to instability growth from deuterium-tritium (DT) ice roughness. These capsule designs contain more ablator mass and leave some beryllium unablated at ignition. By adjusting the level of copper dopant, the unablated mass can increase or decrease, with a corresponding decrease or increase in sensitivity to perturbations. A plastic capsule with the same ablator mass as the beryllium and leaving the same unablated mass also shows this reduced perturbation sensitivity. Beryllium's low opacity permits the creation of 250 eV capsule designs. Its high tensile strength allows it to contain DT fuel at room temperature. Its high thermal conductivity simplifies cryogenic fielding. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872865
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  • 10
    Electronic Resource
    Electronic Resource
    Homogeneous nucleation in supersaturated vapors of polar molecules: Acetonitrile, benzonitrile, nitromethane, and nitrobenzene (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 3356-3368 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The critical supersaturations (Sc) required for the homogeneous nucleation of acetonitrile, benzonitrile, nitromethane, and nitrobenzene vapors have been measured over wide temperature ranges using a thermal diffusion cloud chamber. At Tr=0.44, the experimental results are higher than the predictions of the classical nucleation theory by 20% (CH3NO2), 50% (CH3CN), 57% (C6H5NO2), and 112% (C6H5CN). This trend correlates well with the dipole moments and to a lesser extent with the polarizabilities of these substances. Corresponding states of simple fluids and scaled nucleation law show that CH3CN and CH3NO2 have similar nucleation behavior which is different from that of C6H5CN and C6H5NO2. Correlations with other less polar substances are examined. The scaled law, with Ω (the excess surface entropy per molecule) determined from the temperature dependence of the bulk surface tension, gives a better description of the experimental results than the classical theory with the exception of nitromethane. The results suggest that the classical theory does not take proper account of the dipole–dipole interaction in calculating the free energy of the embryonic droplets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464108
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