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  • 1
    Electronic Resource
    Electronic Resource
    Full-dimensional quantum dynamics study on the mode-specific unimolecular dissociation reaction of HFCO (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 8006-8016 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The mode specificity of the unimolecular reaction of HFCO is studied by six-dimensional quantum dynamics calculations. The energy and mode dependency of the dissociation rate is examined by propagating a number of wave packets with a small energy dispersion representing highly excited states with respect to a specific vibrational mode. The wave packets are generated by applying a set of filter operators onto a source vibrational state. All the information necessary for propagating the wave packets is obtained from a single propagation of the source state, thus allowing a significant decrease of computational effort. The relevant spectral peaks are assigned using the three-dimensional CH chromophore Hamiltonian. The resulting dissociation rate of the CH stretching excited state is in agreement with that obtained from a statistical theory, while the rates of the out-of-plane bending excited states are about one order of magnitude smaller than the statistical rates. A local-mode analysis also shows that the relaxation of the out-of-plane excitation proceeds very slowly within 3 ps. These results clearly indicate weak couplings of the out-of-plane bending excited states with other in-plane vibrational states, which is in qualitative agreement with experimental findings. From a computational point of view, a parallel supercomputer is utilized efficiently to handle an ultra large basis set of an order of 108, and 200 Gflops rate on average is achieved in the dynamics calculations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481400
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of Cr addition on magnetization of Cu-Co alloy. II (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4605-4608 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic behavior of Cu97.7Co2Cr0.3 and Cu97Co2Cr1 alloys was examined in order to investigate the effect of Cr addition to the magnetization of the alloy and prove the presence of Cr atoms in the magnetic clusters. The magnetization of the Cu-Co-Cr alloys is strongly influenced by the amount of Cr added to Cu-Co-Cr alloys. Further, the results indicate there are Cr atoms in the magnetic clusters. The magnetic moment of the cluster was calculated from the experimental data. The results illustrate that the value of the magnetic moment is dependent on the Cr concentration in the noted alloys and this supports the presence of Cr atoms in the magnetic cluster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355929
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of structural irregularity on propagation properties of optical waves in discontinuous magneto-optical media with one-dimensional quasirandom aray structures : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5988-5990 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To elucidate the effect of structural irregularity on propagation properties of optical waves in discontinuous magneto-optical media, theoretical analysis was carried out by employing random matrix technique and a model with one-dimensional quasirandom array structure. The analysis revealed that the effect of structural irregularity was so significant that the dispersion curves of optical waves varied considerably depending on the media structures. However, no matter how the medium structure varies irregularly, dispersion curves of waves always exist within the confines between those of the half (0...01...1) and the alternate (0101...01) structures. This fact suggests that the effect of structural irregularity becomes less significant when the discontinuous media have fine discrete structures, where the dispersion curves of the half and the alternate structures are very close. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362129
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  • 4
    Electronic Resource
    Electronic Resource
    Magneto-optical Faraday effect of discontinuous magnetic media with a one-dimensional array structure (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1611-1624 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To elucidate unique Faraday spectra observed in porous magnetic films, we theoretically analyzed the magneto-optical Faraday effect of discontinuous media with an ideal one-dimensional array structure. The media are constituted by magnetic materials (width DM) and air gaps (width DG) which are aligned interchangingly. Propagation properties of optical waves in the media, such as the dispersion characteristics and the polarization states, were explored circumstantially, and apparent Faraday rotation and ellipticity spectra of the discontinuous media were obtained. The analysis reveals that the apparent Faraday spectra of the media vary to a large extent from those of a continuous medium depending strongly on the media structures. The key factors which govern the magneto-optical effect of the discontinuous media are structural elements of DM and 2(DM+DG): The Faraday spectra are subject to change only when DM〈λ (λ: the wavelength of optical wave in a vacuum). Then, the magneto-optical effect of the magnetic materials is related to mode conversion from TE to TM when 2(DM+DG)〈λ. If DM〈λ〈2(DM+DG), the mode conversions of both directions from TM to TE and TE to TM are possible. The mode conversion dominates the apparent Faraday spectra of the media, causing the enhancement in the Faraday rotation and systematic shift of the spectra toward shorter and/or longer wavelength of the optical waves. These results explain very well the unique Faraday spectra of the porous films. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361005
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  • 5
    Electronic Resource
    Electronic Resource
    Quantum dynamics of unimolecular dissociation reaction HFCO→HF+CO (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9783-9794 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quantum dynamics calculations of the title reaction were performed within planar 4D and 5D models to investigate how the dissociation rate is affected by the change of total energy or vibrational character of the initial states. In the 4D calculations, the possibility for observing the mode specificity in the in-plane modes was examined by generating the initial states that are locally excited with respect to specific vibrational modes and comparing the dissociation rates for these states. In order to generate the appropriate initial states, we employed the spectral filter method combined with the zero-order vibrational Hamiltonian in the bond coordinates. Comparison was also made between the dissociation rate and the intramolecular vibrational energy redistribution (IVR) rate. In the 5D calculations, we have focused on the CH overtone excited states and examined how the dissociation dynamics is changed by the total energy that is above or below the dissociation threshold. We observed quite large fluctuations in the time-dependent rate coefficient for the fifth CH overtone state, which was found to occur due to the resonant oscillations of the CH stretching and bending energies as well as the closeness of the total energy to the dissociation threshold. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477648
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  • 6
    Electronic Resource
    Electronic Resource
    Theoretical study of the dissociation reaction HFCO→HF+CO: New ab initio potential function and classical trajectory analysis (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 6114-6122 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A total of 3261 ab initio energies calculated at the RHF/MP2 level were used to obtain an analytical representation of the potential energy surface (PES) for the title reaction considering all the vibrational degrees of freedom. The analytical potential is constructed by switching three local representations of the PES utilizing a distancelike function, and it reproduces well the ab initio energies up to 20 kcal/mol above the dissociation threshold with the root-mean-square (rms) deviation equal to 1.5 kcal/mol. Two types of classical trajectory studies, i.e., power spectra calculations and product-state distribution analysis, were performed to assess the reliability of the present potential function. The results were found to be in good agreement with the available experimental ones. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474279
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of Cr addition on magnetization of Cu-Co alloy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2453-2457 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization of a Cu-2 at. % Co-0.5 at. % Cr alloy was measured in the temperature range from 77 to 296 K using vibrating sample magnetometer to investigate the effect of Cr addition on magnetization of the Cu-Co alloy. Aging temperature and the range of aging time were 723 K and 1–50 h. The Cu-Co-Cr alloy, as well as the Cu-Co alloy, is found to be superparamagnetic; this indicates the presence of magnetic clusters in the Cu-Co-Cr alloy. From the magnetization versus H/T (H: applied field, T: temperature) plots, magnetization of the Cu-Co alloy can be expressed as a function of H/T while that of the Cu-Co-Cr alloy cannot. Such analytical results suggest that the magnetic moment of the cluster existing in the Cu-Co-Cr alloy is temperature dependent. The temperature dependence of the magnetic moment is attributable to the presence of Cr atoms in the magnetic cluster. From the calculation of nonlinear least-squares fitting in the magnetization, the magnetic moments of the cluster in the Cu-Co-Cr alloy aged for 1 and 5 h were estimated to be about 590 and 4800μB at room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353103
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  • 8
    Electronic Resource
    Electronic Resource
    Combining semiclassical time evolution and quantum Boltzmann operator to evaluate reactive flux correlation function for thermal rate constants of complex systems (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 7335-7349 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The semiclassical (SC) initial value representation (IVR) provides a way for including quantum effects into classical molecular dynamics simulations. Implementation of the SC-IVR to the thermal rate constant calculation, based on the reactive flux correlation function formalism, has two major obstacles: (1) the SC integrand may be highly oscillatory with respect to the initial phase space variables; and (2) matrix elements of the Boltzmannized flux operator, which are crucial in generating the initial (or final) distribution for the SC trajectories, are generally not available in analytic forms. In this paper, we present practical ways of overcoming these two barriers for the SC calculation of thermal rate constants. For the first problem, we show that use of a symmetric flux–flux correlation function, together with the generalized Filinov transformation technique, can significantly smooth the corresponding SC integrand and make the calculation practical for quite large systems. For the second problem, we propose a general method for evaluating matrix elements of the Boltzmannized flux operator "on-the-fly," based on the combination of the imaginary-time path integral technique with the Metropolis random walk algorithm. Using these approaches, it is shown that thermal rate constants can be obtained for systems with more than 100 degrees of freedom, as well as for reactions in the deep tunneling regimes where quantum effects are significant. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1464539
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  • 9
    Electronic Resource
    Electronic Resource
    Antibody-catalyzed double stereoselection in fluorinated materials (1991)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 113 (1991), S. 8573-8575 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00022a083
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  • 10
    Electronic Resource
    Electronic Resource
    Nanometer-scale local oxidation of silicon using silicon nitride islands formed in the early stages of nitridation (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2222-2224 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the silicon nitride (SiN) nucleation on the Si(111) 7×7 surface due to thermal nitridation with scanning tunneling microscopy (STM), and applied the resultant small SiN islands to oxidation masks in local oxidation of Si (LOCOS) process for fabrication of nanometer-scale Si structures. The nitrides appear as dark regions in STM images and the average size increases (the density decreases) with increasing nitridation temperature. When the nitrided surface is successively oxidized in the etching mode with a reaction of Si+O2→SiO↑, the nitrides turn to bright regions by selective etching of the clean 7×7 regions and the brightness (height) increases with increasing etching time. Thus, the microscopic LOCOS process is demonstrated and nanometer-scale Si pillars are fabricated. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117172
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