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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of high-energy plasma formation in hydrogen (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6718-6725 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Analysis is presented on the position, velocity, acceleration, mass, size, and shape of the hydrogen plasma formed by a 88-kJ pulse within a coaxial injection and accelerated into a coaxial expansion chamber. Within the expansion chamber of the 1.25-m-long apparatus, the velocity was obtained near the positions of three sets of current probes and exceeds 44 cm/μs. The acceleration of the plasma in the acceleration chamber increases with time to values approaching 30 cm/μs2 and the plasma length averages nearly 30 cm. Numerical inversion of the circuit current measured by a current probe near the base of the injection chamber yields the time variation of the circuit inductance produced by the motion of the plasma. From the inductance the position of the plasma during the pulse is inferred throughout the whole of the apparatus up to the end wall of the expansion chamber. The inversion analysis agrees with the probe analysis if it is assumed that the plasma extrudes from the injection chamber at approximately the radius of that chamber. Mass is lost by the accelerated plasma and specific mass values are derived, versus time, for cases when plasma momentum is conserved and not conserved. Both values extrapolate, at zero time, to the measured mass of injected hydrogen. There is good indication that the plasma survives reflection from the end wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349846
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative time-resolved observations of ground-state zinc atoms, methyl radicals, and excited CH radicals resulting from the 193 nm photodissociation of dimethylzinc (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6962-6971 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ArF laser photodissociation dynamics of dimethylzinc at 193 nm have been studied, and their implications for the growth of ZnSe thin films are discussed. A broadband, vacuum ultraviolet argon plasma emission has been used to acquire time-resolved absorption profiles from ground-state Zn atoms and methyl radicals. Time-resolved fluorescence from excited CH radicals has also been studied. The results indicate that the Zn concentration remains constant from 100 ns to 2 ms after the dissociating ArF pulse, indicating that this system is a good source for free Zn atoms. The CH3 radicals are formed immediately after the dissociation pulse and recombine within several hundred microseconds to form ethane. There was no indication of monomethylzinc (MMZn) formation, and the detected CH radical is likely to combine with H2 to form CH3 within several microseconds. This implies that the major sources for carbon contamination in the growth process (CH3, MMZn, CH) are unlikely to reach the growth surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355046
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  • 3
    Electronic Resource
    Electronic Resource
    Carbon diffusion in uncoated and titanium nitride coated iron substrates during microwave plasma assisted chemical vapor deposition of diamond (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4643-4647 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Auger electron spectroscopy has been employed to investigate the effectiveness of thin films of TiN as barriers to carbon diffusion during chemical vapor deposition (CVD) of diamond onto Fe substrates. Auger depth profiling was used to monitor the C concentration in the TiN layer, through the interface and into the substrate both before and after CVD diamond deposition. The results show that a layer of TiN only 250 A(ring) thick is sufficient to inhibit soot formation on the Fe surface and C diffusion into the Fe bulk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352119
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  • 4
    Electronic Resource
    Electronic Resource
    Accurate multireference configuration interaction calculations of the potential energy function and the dissociation energy of N2 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1264-1270 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The potential energy function of the N2 molecule is calculated using the internally contracted multireference CI method (CMRCI) and complete active space SCF (CASSCF) reference wave functions. A full CI calculation in a DZP basis set is used to estimate the errors associated with the CMRCI wave function. The dependence of the computed spectroscopic constants and the dissociation energy on the basis set is also investigated. Uncontracted and segmented basis sets are compared with ANO (atomic natural orbital) and other generally contracted basis sets. It is found that the energy optimized "correlation consistent'' basis sets of Dunning yield substantially better results than ANO basis sets of the same size. In the largest calculations, which included up to h type basis functions and also accounted for core–core and core–valence correlation effects, the remaining errors are 0. 0003 A(ring), 8 cm−1, and 0.7 kcal/mol for re, ωe, and De, respectively. The inclusion of an i type basis function reduces the error in the dissociation energy to 0.3 kcal/mol (0.013 eV).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460696
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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical assignment of the visible spectrum of singlet methylene (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 118-132 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The potential energy surfaces of the two lowest-lying singlet electronic states of methylene (CH2) are determined by internally contracted multireference configuration interaction calculations, using a full-valence reference space, with an extended Gaussian basis set. The rotation–vibration levels on these surfaces are calculated by diagonalizing the rovibrational Hamiltonian matrix in a contracted basis. The rovibronic mixing due to the strong Renner–Teller interaction in this system is treated through the Coriolis term in the kinetic energy operator, using geometry-dependent electronic angular momentum matrix elements calculated from ab initio wave functions. The agreement between experiment and this high-quality ab initio calculation is sufficiently good that the calculation can be used to assign the observed vibronic bands in this very complex spectrum, where 90% of the observed lines remain unassigned. Many of the previous vibronic band labels are found to be incorrect. Most of the K〉0 bands previously labeled b˜ 1B1 are actually predominantly a˜ 1A1 in character, and the vibrational numbering of their b˜ 1B1 components are also incorrect. This work demonstrates the importance of supplementing experimental data with good quality ab initio calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460385
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  • 6
    Electronic Resource
    Electronic Resource
    On obtaining interatomic potentials from multiproperty fits to experimental data (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 296-309 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High-resolution differential cross section (DCS) and accurate new limiting diffusion measurements for all the unlike-pair He+rare-gas systems are combined in constructing new multiproperty interatomic potentials. The new potentials predict most properties available for these systems, including independent high-resolution DCS measurements. Remaining discrepancies with earlier multiproperty potentials for HeKr and HeXe are attributed to incompatibilities among data sets used in the multiproperty fitting procedure. It is also shown that the 5% difference in well depths between two recently proposed potentials for HeXe is due to some of the data used in constructing these potentials, and that the DCS measurements of those studies are mutually consistent. Finally, the present potentials are refined slightly for agreement with high-energy cross section measurements. At the present level of reliability for DCS and dilute-gas data, it seems likely that high-resolution DCS and accurate (limiting) diffusion measurements will assist in determining He+molecule potentials. These two properties are particularly useful because they are independent of uncertainties in the corresponding molecule+molecule potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460397
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  • 7
    Electronic Resource
    Electronic Resource
    The electric field response of periodic chemical wave trains in folded slow manifold systems (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 1062-1068 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The properties of periodic chemical wave trains in an applied electric field are analyzed for a two variable model. The model reduces to a free boundary problem in the limit where certain reactions are fast. The dispersion relation (frequency vs wave vector) was obtained and compared with the field-free case studied earlier. Electrochemical periodic wave trains were shown to emerge as a bifurcation at a fixed wave vector as the field strength decreases through a wavelength dependent critical value. As the field exceeds its critical value, periodic waves of a given wavelength are annihilated at finite amplitude. The results presented here differ significantly from the small amplitude bifurcation analysis whereby the wave amplitude passes through zero as the field exceeds its critical value. No finite amplitude extinction is observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458168
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  • 8
    Electronic Resource
    Electronic Resource
    Transient photophysical hole-burning spectroscopy of the hydrated electron: A quantum dynamical simulation (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6916-6924 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results for the time-dependent adiabatic eigenspectrum of an electron in water evolving in dynamic equilibrium have been obtained via quantum molecular dynamics simulation and used to evaluate the results expected from time-resolved transient optical hole-burning experiments. The dependence on excitation frequency and pulse length have been explored. The calculated results indicate that a relatively broad hole is created, but that, for ultrashort pump–probe time delays (≤100 fs) and comparably short pulses, the shape is distinctly different from the equilibrium spectrum. A slower component in the spectral evolution is also present, but appears likely to be difficult to distinguish experimentally. The shape of the absorption deficit is characteristic of the inhomogeneously broadened 1s, 2p-type electronic state structure found previously to underlie the equilibrium spectrum, and distinguishes between this description and a number of proposed alternatives. With pulse durations comparable to the best now available, the phenomenon appears experimentally accessible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456266
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  • 9
    Electronic Resource
    Electronic Resource
    Anisotropic intermolecular potentials for HeC2H2, HeC2H4, and HeC2H6, and an effective spherical potential for HeCHF3 from multiproperty fits (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4218-4227 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Differential cross section (DCS) measurements are reported for scattering of a He atomic beam by crossed beams of C2H2, C2H4, C2H6, and CHF3. In addition, interaction virial measurements and accurate limiting diffusion measurements are presented for these systems. Damping of the DCS diffraction oscillations is used to extract anisotropic intermolecular potentials, which are constrained in multiproperty fits to accurately reproduce the dilute gas data. The radial anisotropies determined are in the sequence C2H6〉C2H4∼C2H2〉CHF3, as sampled by the He probe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453830
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  • 10
    Electronic Resource
    Electronic Resource
    On the correlation between like ion pairs in water (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4046-4047 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The consequences of the subtle balance of intermolecular forces for like charge interionic correlations in solution are considered. The potential of mean force (PMF) for Cl−–Cl− and Na+–Na+ ion pairs using simple point charge (SPC and SPC/E) water models are examined in detail, and it is demonstrated that the results depend qualitatively on the details of the model. Features in the ion–ion cavity potential are shown to be responsible for much of the observed sensitivity with respect to parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461859
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