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  • 1
    Electronic Resource
    Electronic Resource
    Bi- and unimolecular resonances of the collinear reaction F+DBr(arrow-right-and-left)FDBr(arrow-right-and-left)FD+Br (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 6191-6199 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction probability function P(ν'←ν||E) of the bimolecular collinear reaction F+DBr(ν)→FD(ν')+Br shows sharp resonance peaks at certain collision energies Ebi. On the other hand, the unimolecular dissociation FDBr*(ν1ν3)→F+DBr(ν), FD+Br(ν) exhibits long-lived behavior for particular resonance wave functions Ψν1ν3 at energies Euni. Good numerical agreement is found in a comparison of bi- and unimolecular resonance energies and lifetimes by two complementary methods: (i) S-matrix propagation in hyperspherical coordinates for the bimolecular reaction; (ii) the diagonally corrected vibrational adiabatic hyperspherical (DIVAH) method to determine unimolecular resonances, coupled with the fast Hankel transform (FHT) method to propagate them in time. The agreement found suggests a correlation between bi- and unimolecular resonances by the reaction mechanism F+DBr(ν)(arrow-right-and-left)FDBr*(ν1ν3)(arrow-right-and-left)FD(ν')+Br, where the unimolecular resonance states Ψν1ν3 serve as traps or doorway states, blocking or catalyzing the bimolecular reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454750
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  • 2
    Electronic Resource
    Electronic Resource
    Exact time-dependent quantum mechanical dissociation dynamics of I2He: Comparison of exact time-dependent quantum calculation with the quantum time-dependent self-consistent field (TDSCF) approximation (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 2760-2765 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrational predissociation dynamics of a collinear model of the I2(v)He cluster is studied by numerically exact time-dependent quantum mechanics, and by the time-dependent self-consistent field (TDSCF) approximation. The time evolution for the initial excitation levels v=5, 11, 22 is explored. Excellent agreement is found between the TDSCF and the exact evolution of the wave packet; in particular the approximation reproduces well the dephasing events in the dynamics, and the measurable predissociation lifetimes. The results are very encouraging as to the applicability of quantum TDSCF as a quantitative tool in the study of van der Waals predissociation dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453063
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Lifetimes of local and hyperspherical vibrational resonances of ABA molecules (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2626-2638 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The complete spectrum of vibrationally excited ABA* molecular resonance lifetimes is evaluated using the simple Rosen–Thiele–Wilson model of coupled Morse oscillators. Two complementary methods are used: First, unimolecular dissociative resonance wave functions are propagated in time by the Fourier method, where the initial wave functions are obtained as an approximation by linear combinations of symmetry-adapted products of Morse functions. Second, bimolecular reaction S matrices are propagated along the hyperspherical radius of the system giving the diagonalized lifetime matrix, which is analyzed for resonance lifetimes and energies. The resulting uni- and bimolecular resonance energies agree within ±0.002 eV and the lifetimes within ±30%. Uni- and bimolecular assignments of gerade (+) and ungerade (−) ABA* symmetries agree perfectly. On the average, the unimolecular decay times decrease as the resonance energies increase from the ABA*→A+BA to about 3/4 of the A+B+A dissociation threshold; even more highly excited resonances tend to be slightly more stabilized. Superimposed on this overall nonmonotonous energy dependence is a strong, 1–2 orders of magnitude variation of lifetimes, indicating substantial mode selectivity for the decay of individual resonances, irrespective of the excitation energy. The mode selectivity is investigated for hyperspherical mode resonances with lobes extending across the potential valleys, in contrast with local mode resonances with frontier lobes pointing towards the valleys. On the average, hyperspherical mode resonances decay at a slower rate than local mode resonances. This conclusion agrees with our previous analysis of low energy ABA* resonances, and with Hose and Taylor's analysis of the Hénon–Heiles system. However, these correlations are also violated by several important exceptions: the ABA* system has many slowly, but also a few rapidly, decaying hyperspherical resonances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452754
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamics of hyperspherical and local mode resonance decay studied by time dependent wave packet propagation (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 993-1004 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time dependent wave packet propagation of resonance states of ABA molecules is used to demonstrate the correlation between the directionality of the lobes of the wave functions and mode selectivity of the unimolecular decay. This correlation was inferred by Hose and Taylor. The molecule is modeled by the Thiele–Wilson coupled Morse oscillators. A near-degenerate pair of resonances with extreme motions is studied in detail: The local "bond'' mode with lobes pointing towards the exit valleys of the potential decays about 30 times faster than the hyperspherical "restricted precession'' mode with dominant lobe on the potential ridge. This is in close analogy to mode selectivity in the Hénon–Heiles system. The wave function propagation technique also yields detailed insight into the dissociation mechanism. Out of several choices, only a single lobe penetrates into the exit valley. For the local mode resonance vibrational predissociation starts out primarily from extended vibrationally excited diatomic configurations, A↔B(ν*=1)⋅ ⋅ ⋅A→AB(ν'=0)+A. However, the hyperspherical mode resonance prefers compressed diatomic geometry just before dissociation, AB(ν*=3)⋅ ⋅ ⋅A→AB(ν'=0)+A. The results imply some general criteria for mode selective unimolecular chemical reactions, as well as a successful numerical test of the preparation of resonance wave functions and their propagation by the Fourier method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449426
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  • 5
    Electronic Resource
    Electronic Resource
    A parallel interior point algorithm for linear programming on a network of transputers (1993)
    Springer
    Annals of operations research 43 (1993), S. 49-86 
    Details
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract Interior Point algorithms have become a very successful tool for solving large-scale linear programming problems. The Dual Affine algorithm is one of the Interior Point algorithms implemented in the computer program OB1. It is a good candidate for implementation on a parallel computer because it is very computing-intensive. A parallel Dual Affine algorithm is presented which is suitable for a parallel computer with a distributed memory. The algorithm obtains its speedup from parallel sparse linear algebra computations such as Cholesky factorisation, matrix multiplication, and triangular system solving, which form the bulk of the computing work. Efficient algorithms based on the grid distribution of matrices are presented for each of these computations. The algorithm is implemented in occam 2 on a square mesh of transputers. The resulting parallel program is connected to the sequentialFortran 77 program OB1, which performs the preprocessing and the postprocessing. Experimental results on a mesh of 400 transputers are given for a test set of seven realistic planning and scheduling problems from Shell and seven problems from the NETLIB LP collection; the results show a speedup of 88 for the largest problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02024486
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    Paper (German National Licenses)
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