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  • American Institute of Physics (AIP)  (44)
  • National Academy of Sciences  (23)
  • 1985-1989  (67)
  • 1
    Electronic Resource
    Electronic Resource
    Dimensional scaling as a symmetry operation (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7791-7796 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The scaling of the Schrödinger equation with spatial dimension D is studied by an algebraic approach. For any spherically symmetric potential, the Hamiltonian is invariant under such scaling to order 1/D2. For the special family of potentials that are homogeneous functions of the radial coordinate, the scaling invariance is exact to all orders in 1/D. Explicit algebraic expressions are derived for the operators which shift D up or down. These ladder operators form an SU(1,1) algebra. The spectrum generating algebra to order 1/D2 corresponds to harmonic motion. In the D→∞ limit the ladder operators commute and yield a classical-like continuous energy spectrum. The relation of supersymmetry and D scaling is also illustrated by deriving an analytic solution for the Hooke's law model of a two-electron atom, subject to a constraint linking the harmonic frequency to the nuclear charge and the dimension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457247
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  • 2
    Electronic Resource
    Electronic Resource
    Solution of the Percus–Yevick approximation of the multicomponent adhesive spheres system applied to the small angle x-ray scattering from microemulsions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4482-4490 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper describes the application of the numerical solution of the Percus–Yevick approximation for a multicomponent system of sticky hard spheres to small angle x-ray scattering experiments. The effect of polydispersity on the pair correlation function is quantitatively described, thus enabling the analysis of experimental data. In this way quantitative estimates of the size distribution width, interaction radii and the measure of attraction between particles can be obtained. The attractive interaction in a system of sticky spheres is known to give rise to a transition analogous to a gas–liquid phase transition. The effect of polydispersity on this transition is discussed. Finally it is shown how the model can be used to describe small angle x-ray scattering from an AOT microemulsion system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456635
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  • 3
    Electronic Resource
    Electronic Resource
    Numerical simulations of electron spin resonance spectra: Unified description and comparison of the Lanczos algorithm, the generalized Mori method, and Padé approximants (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 4505-4513 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A comprehensive study of the various related methods for the solution of the stochastic Liouville equation is presented. The methods are essentially based on moment expansions and continued fraction representations and lead to efficient algorithms for carrying out numerical simulations of electron spin resonance (ESR) spectra. The convergence, stability, and error propagation are discussed and compared using the model system of an axially symmetric nitroxide molecule tumbling isotropically in solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454790
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  • 4
    Electronic Resource
    Electronic Resource
    Why separable vibrational modes dominate spectra (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2071-2072 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456000
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  • 5
    Electronic Resource
    Electronic Resource
    Intensity distribution in rotational line spectra. II. Analysis of the fluctuations in the Doppler-free S1←S0 spectrum of benzene (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 4633-4637 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The fluctuations in the intensities of rotational bands in the S1 manifold of benzene are analyzed in detail. The extent of mixing is found to increase with energy and those bands which could not be assigned are found to have an intensity distribution characteristic of the chaotic limit. At a given energy, those bands which borrow intensity due to resonance coupling are more mixed and the C6D6 bands are more strongly coupled than those of C6H6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454804
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of transition moment directions in molecules of low symmetry using polarized fluorescence. I. Theory (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4095-4102 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theoretical description of angle-resolved fluorescence depolarization experiments of dye molecules in stretched polymer films is presented. It is shown how the technique can be used for the determination of transition moment directions in organic molecules of low symmetry. The application of these angle-resolved measurements to the determination of the direction of the transition moments in a number of dye molecules is discussed in the following paper. The theoretical treatment implicitly assumes that the motions of the fluorescent molecules are slow on the time scale of their excited state lifetime (in the order of ns) so that their orientation is identical at the times of absorption and emission. Furthermore the molecules are taken to be uniaxially distributed around the stretch direction of the polymer film and it is shown how this can be checked experimentally. The macroscopic orientational distribution is assumed to be invariant for a rotation of 180° of the molecules around a "mechanical'' symmetry axis chosen in the molecular frame as well as to a reflection in the molecular plane (C2v D2h symmetry). The treatment presented makes use of the Wigner rotation matrix formalism in the description of the fluorescence intensities in terms of molecular orientational properties (order parameters and angles between transition moments and the mechanical symmetry axis). The advantge of this formalism is the ease with which rotational transformations are carried out between molecular and laboratory frames and further that the symmetry properties of both the molecules and the system are treated in a simple and general way.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455767
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  • 7
    Electronic Resource
    Electronic Resource
    Determination of transition moment directions in molecules of low symmetry using polarized fluorescence. II. Applications to pyranine, perylene, and DPH (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4103-4111 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The application of angle-resolved fluorescence depolarization techniques to the simultaneous determination of the directions of the transition moments and orientational order of dye molecules incorporated into uniaxially stretched polymer films is discussed and illustrated. The directions of the transition moments of pyranine molecules are determined in a general way, on exciting the molecules in two distinct electronic transitions and monitoring the fluorescence emission under the same conditions. This assumes that the fluorescence emission occurs via the same transition moment for every excited absorption band. Experiments on perylene molecules show that the directions of the transition moments can also be determined from measurements utilizing a single electronic absorption band. In this case the orientational distribution of the molecules is assumed to have the form given by the maximum entropy method. Finally, it is shown the directions of the transition moments of DPH molecules in unstretched polymer films can be determined with this technique. It appears that these molecules are oriented to a very small, yet measurable, extent in unstretched films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455768
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  • 8
    Electronic Resource
    Electronic Resource
    Broad spectral features in the stimulated emission pumping spectrum of acetylene (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5972-5974 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrational spectrumof acetylene is reported. This is the stimulat emission pumping spectrum obtained by stimulated downward transition from an upper electronic state to the ground electronic surface.Broad band and high resolution spectra were recorded at 25840−27250 wave numbers.(AIP)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454510
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  • 9
    Electronic Resource
    Electronic Resource
    Erratum: Determination of transition moment directions in molecules of low symmetry using polarized fluorescence. I. Theory [J. Chem. Phys. 90, 4095 (1989)] (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3281-3281 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457671
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  • 10
    Electronic Resource
    Electronic Resource
    Energy flow pathways and their spectral signatures in vibrationally excited acetylene (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 3379-3381 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Algebraic methods and classical trajectory studies for a model Hamiltonian which includes all in-plane vibrational modes are used to elucidate the origin of spectral structure in the stimulated emission spectra of acetylene. The molecular oscillators responsible for previously established gateway states are determined as well as a plausible description of the overall IVR mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454948
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