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  • American Institute of Physics (AIP)  (31,708)
  • Copernicus
  • 1985-1989  (32,011)
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Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Further theoretical studies on B2H4 and B2H+4 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5118-5119 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vertical ionization potentials of the D2d and C2v structures of B2H4 are reported at the G1 level of ab initio molecular orbital theory. The results support the interpretation by Ruscic, Schwarz, and Berkowitz of their new photoionization experiment in terms of a C2v bridged structure of B2H4. In addition, the bridged C2v B2H+4 cation is found to have a very small barrier to inversion (1 kcal/mol).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457605
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  • 2
    Electronic Resource
    Electronic Resource
    Approximate radii for singly negative ions of 3d, 4d, and 5d metal atoms (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5123-5124 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The radii and electrostatic potential of singly−negative ions of the 3d,4d and 5d transition series have bee calculated. This gives a quantitative estimate of the size of these ions.(AIP)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457607
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  • 3
    Electronic Resource
    Electronic Resource
    A theoretical study of multidimensional nuclear tunneling in malonaldehyde (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4061-4072 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Various aspects of the intramolecular proton transfer in malonaldehyde have been investigated theoretically within the reaction surface Hamiltonian framework, which was recently applied with a two-dimensional surface to this molecule by Carrington and Miller. The present calculation, which involves a three-dimensional reaction surface and a high level of ab initio accuracy, gives a tunneling splitting which is ∼50% smaller than experiment and a hydrogen/deuterium isotope effect that is within 40% of experiment with no adjustable parameter. The vibrational wave function has been analyzed to extract an effective curvilinear tunneling path on the hypersurface. The path calculations, and other analysis, clearly demonstrate the limitations of one-dimensional models for polyatomic tunneling systems like malonaldehyde. In addition, tunneling splittings have been calculated for excited vibrational states of malonaldehyde, leading to new insight into the multidimensional character of proton transfer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456836
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  • 4
    Electronic Resource
    Electronic Resource
    Solvent influence on the magnetic field effect of polymethylene-linked photogenerated radical ion pairs (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4098-4105 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The solvent viscosity and polarity dependence of the magnetic field effect in polymethylene-linked radical ion pairs, which were generated by photoinduced intramolecular electron transfer in compounds of the type pyrene–(CH2)n–N,N-dimethylaniline, has been studied. A stochastic Liouville equation is used, in which the dynamics of the polymethylene chain, the spin Hamiltonian as a function of the varying radical distance (exchange interaction), and a distance-dependent back electron transfer rate are incorporated. The results are compared with predictions made on the basis of the (static) subensemble approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457624
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  • 5
    Electronic Resource
    Electronic Resource
    Direct determination of scattering time delays using the R-matrix propagation method (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4106-4110 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A direct method for determining time delays for scattering processes is developed using the R-matrix propagation method. The procedure involves the simultaneous generation of the global R matrix and its energy derivative. The necessary expressions to obtain the energy derivative of the S matrix are relatively simple and involve many of the same matrix elements required for the R-matrix propagation method. This method is applied to a simple model for a chemical reaction that displays sharp resonance features. The test results of the direct method are shown to be in excellent agreement with the traditional numerical differentiation method for scattering energies near the resonance energy. However, for sharp resonances the numerical differentiation method requires calculation of the S-matrix elements at many closely spaced energies. Since the direct method presented here involves calculations at only a single energy, one is able to generate accurate energy derivatives and time delays much more efficiently and reliably.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456839
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  • 6
    Electronic Resource
    Electronic Resource
    The Hamiltonian formulation of configurationally constrained bimolecular kinetics: A test against simulations (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4111-4117 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Hamiltonian-based model developed by the authors [N. J. Cotes and M. G. Sceats, J. Chem. Phys. 89, 2816 (1988)] for bimolecular reactions which exhibit severe configurational restrictions, such as orientational requirements for reaction at surface sites, provides an analytical expression for the reaction rate which involves the evaluation of the potential of mean force along the radial coordinate that describes the binding. The expression for the reaction rate is evaluated for the case of a charged molecule interacting with a binding site on a dipolar particle. The results of the model are compared with the multidimensional Brownian-dynamics simulations of Northrup et al. [J. Chem. Phys. 84, 5536 (1986)] and excellent agreement is obtained in the diffusion limit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456840
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  • 7
    Electronic Resource
    Electronic Resource
    Cage effect for the abstraction of H from H2O in Ar matrices (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4128-4133 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A red wing in the absorption of H2O in the first continuum which extends beyond 200 nm is induced by the matrix. A threshold energy of 6.95 eV is found for the quantum efficiency of permanent dissociation of H2O into OH and H. This corresponds to an additional barrier of 1.8 eV due to the matrix cage. The barrier is attributed to the sum of repulsive H–Ar pair potentials in an interstitial site of D3 symmetry, which has to be surmounted by the H atom on the way from the initial substitutional H2O site to the final stable Oh site of the abstracted H atom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456842
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular integrals with Slater basis. II. Fast computational algorithms (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4213-4222 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new algorithm for the calculation of molecular integrals involving STOs is reported. The algorithm enables us to obtain every two-center one-electron integral and the long-range many-center one- and two-electron integrals. The efficient implementation of the algorithm is discussed and its performance is thoroughly tested. The analysis on the stability of the relations employed in the calculation of multipolar moments is included. Futhermore, the computer time required to carry out each step (construction of basic matrices, calculation of multipolar moments, and calculation of two-electron integrals) has also been analyzed. The range of validity of this approach is shown in several molecular integrals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456800
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  • 9
    Electronic Resource
    Electronic Resource
    Application of projection techniques to the electron correlation problem (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4223-4228 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: By applying projection techniques a unified description of weakly and strongly correlated electronic systems can be given. For that purpose the theory is formulated in Liouville instead of Hilbert space. By introducing an appropriate metric in terms of cumulants it is ensured that all energies are size consistent. An energy expression is derived which is a generalization of Goldstone's linked cluster theorem for arbitrary Hamiltonians. It is suitable for applying the projection method of Zwanzig and Mori. The equations for the correlation energy within the Local Ansatz and within coupled electron pair approximation CEPA-2 follow straightforwardly from the present theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456801
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  • 10
    Electronic Resource
    Electronic Resource
    Cumulant methods and short time propagators (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4242-4248 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The present paper clarifies a number of issues concerning the general problem of constructing improved short time quantum mechanical propagators. Cumulant methods are shown to be a particularly convenient tool for this task. Numerical results comparing methods based on partial averaging and on gradient approaches are presented for simple model problems and for many particle quantum fluids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456803
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