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  • 1
    Electronic Resource
    Electronic Resource
    Semiclassical quantization by circuit counting: Application to SO2 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 882-888 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper a semiclassical quantization method is developed whose formulation and application is simple, general and accurate. We call this method semiclassical quantization by circuit counting (SQCC). SQCC is based upon evaluating the action integral along a trajectory until it undergoes a near recurrence. Several near recurrences are used to obtain a set of independent equations which can then be inverted to yield the actions for the trajectory. Once the actions are obtained a linear extrapolation is used to calculate semiclassical energies. We apply the method to two model systems: (1) three uncoupled Morse oscillators and (2) a realistic three degree of freedom model of SO2. SQCC is found to work very well for these systems. We discuss some of the advantages and disadvantages of SQCC and its application to systems with more than three coupled molecular degrees of freedom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455211
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  • 2
    Electronic Resource
    Electronic Resource
    Cylindrical manifolds in phase space as mediators of chemical reaction dynamics and kinetics. I. Theory (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 8310-8328 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A microcanonical kinetic theory of reactions based upon the structure within phase space is developed. It is shown that the dynamics of reaction across an energetic barrier is mediated by invariant manifolds embedded in phase space that have the geometry of simple cylinders. The ideas are developed by considering molecular systems modeled by two vibrational degrees of freedom, a reaction coordinate and a "bath'' coordinate. The kinetic theory is constructed by focusing on the dynamics between n mapping planes ("n-map'') and the "reactive island'' (RI) structure within them. We discuss how the structure of the conformer population decay in isomerization reactions can be obtained from the RI kinetic model. Formal solutions of the kinetic equations are discussed with specific attention given towards the calculation of the isomerization reaction rate. The formal theory is developed in Paper I of this series. Numerical considerations and applications to the reaction dynamics of model molecular systems with two degrees of freedom will be given in Paper II and extension of the theory and applications to multidimensional systems will be given in Paper III.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460116
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  • 3
    Electronic Resource
    Electronic Resource
    Cylindrical manifolds in phase space as mediators of chemical reaction dynamics and kinetics. II. Numerical considerations and applications to models with two degrees of freedom (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 8329-8341 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In Paper I we discussed the existence of cylindrical manifolds embedded in phase space which mediate the dynamics of chemical reactions. A kinetic theory of population decays and decay rate constants was developed which we called "reactive island'' (RI) theory. In this paper we discuss the details of the numerical implementation of the theory and then apply it to several molecular models (with two coupled degrees of freedom) representing isomerization between two and three states. Numerical simulations of population decays and asymptotic decay rate constants are compared to the RI theoretical predictions as well as the predictions from the Purely Random Theory (PRT) and Transition State Theory (TST) of reactions. Of the ten systems studied we find that RI theory is generally in good to excellent agreement with the numerical simulations. Only one system exhibits significant deviation between the RI and numerical results. This deviation is seen to be a result of a strong intraconformer dynamical bottleneck. Finally, we compare the theoretical prediction and the numerical simulation for the average n-map mapping time Trxn and find that the agreement, within numerical error, is exact irrespective of the character of the dynamics (i.e., chaotic or regular).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460065
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  • 4
    Electronic Resource
    Electronic Resource
    Eigenstates of bilinears in paraboson operators and their inverses (1993)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 34 (1993), S. 2875-2892 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The inverse of paraboson annihilation and creation operators is introduced. The properties of these operators, their number state representation and commutation relations are discussed. Also introduced are the family of eigenstates of bilinears in paraboson operators and their inverses; and study the nonclassical properties, namely, squeezing and fluctuations in number of parabosons in these eigenstates. It is observed that a family of the eigenstates of a+−1a is the parasqueezed vacuum, S(σ)||0,α〉. Similarly, a family of the eigenstates of aa+−1 is the parasqueezed first state, S(σ)||n=1,α〉.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.530102
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  • 5
    Electronic Resource
    Electronic Resource
    Some trigonometric identities encountered by McCoy and Orrick (1995)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 36 (1995), S. 5098-5109 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A proof is given for the trigonometric identities (1.1)–(1.5) arising in the perturbative treatment of chiral Potts model. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.531345
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  • 6
    Electronic Resource
    Electronic Resource
    Correlated states and collective transition operators for multilevel atomic systems. I (1988)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 29 (1988), S. 510-515 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The correlated states of an assembly of N multilevel atoms interacting with resonant radiation fields are determined. On the basis of the duality between the permutation group and the linear group, one can construct the internal states for an assembly of N atoms, with n levels each. The possible states are determined by various allowed Young diagrams, corresponding to various representations of the permutation group SN. The collective transition operators are obtained as the generators of the group SU(n).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.528042
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  • 7
    Electronic Resource
    Electronic Resource
    Correlated states and collective transition operators for multilevel atomic systems. II. Symmetry properties (1988)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 29 (1988), S. 2443-2449 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The symmetry properties of the N-particle multilevel system are studied. For indistinguishable particles, the total wave function must be either symmetric or antisymmetric in the exchange of any two particles. The internal states of the multilevel system are combined with suitable spatial wave functions to produce a totally symmetric or antisymmetric wave function. The problem of degeneracy and the method of combining a given permutational symmetry of the internal wave function with the same or the conjugate symmetry for the spatial part are described. It is found that Young's diagram corresponding to the given irreducible representation of the permutation group plays an important role.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.528132
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  • 8
    Electronic Resource
    Electronic Resource
    Microwave solitons in magnetic films (invited) (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5365-5365 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonlinear waves in the form of solitons in magnetic films are attracting attention because of the interesting possibility of making novel spatial, and temporal, soliton devices that will operate in the technologically important microwave (GHz) frequency window. Some fascinating pioneering experimental work has been performed in this area and there is now every possibility that manipulation of solitonlike microwave pulses will be the basis of an entirely new range of devices. Both theory and experiment show that solitons are extremely robust and behave rather like particles. Magnetic films look set to become as successful as optical fibers in supporting bright envelope solitons; yet soliton behavior can often seem hard to comprehend. While they are subtle in their behavior they can be understood from many points of view that are physically, or mathematically, based. This presentation will explain what bright microwave envelope solitons are, drawing upon as much physical insight and analogy as possible. The necessary and sufficient conditions for soliton existence will be carefully set out, especially with respect to their relationship to the input conditions of a device. A substantial number of numerical examples will be used and the prospects for major expansion in the experimental area will be assessed. In the latter part of the presentation some important applications for solitons will be addressed. These will include the analysis of a switching device but logic devices, and various forms of pump–probe arrangements, will also be retrieved. Finally, the optimistic view that solitons in magnetic materials are now realistic tools will be expressed and the opportunities provided by dark and higher-dimensional solitons will be discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361915
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  • 9
    Electronic Resource
    Electronic Resource
    Laser heating and photoluminescence in GaAs and AlxGa1−xAs (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2469-2471 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature band-to-band photoluminescence of GaAs and AlGaAs excited by the 514.5 nm line of an argon ion laser beam was used as a probe to measure the temperature at the focused laser spot. A combined study of the dependence of band-gap energy on increasing laser power density and temperature was undertaken. The band-gap variation with temperature has been correlated with laser induced temperature at the focused laser spot as a function of laser power density. The induced temperature is lower than anticipated from the theories for cw laser heating. This disagreement can be explained by the contribution of photoexcited carriers to the thermal conductivity, which is not considered by theories available for laser heating in semiconductors. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112710
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of hydrogenation on photoluminescence of GaAlAs grown by molecular beam epitaxy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 6058-6060 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of hydrogenation on GaAlAs layer grown by molecular beam epitaxy stored over a long period of time was investigated using photoluminescence (PL) measurement. Upon hydrogenation, the defects in the GaAlAs are passivated and the PL intensity increased many times. Hydrogenation changes the energy of the defect produced on storage of GaAlAs and new features appear in excitonic emissions. On annealing the hydrogenated GaAlAs at temperatures (approximately-greater-than)500 °C, the defects are depassivated and the PL intensity degraded. Hydrogenation improves the PL intensity of emission from a stack of GaAs/GaAlAs quantum wells (QW) of different well widths by a factor which varies with the depth of the QW from the surface. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359129
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