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  • 1
    Electronic Resource
    Electronic Resource
    Unusual conical intersections in the Jahn–Teller effect: The electronically excited states of Li3 (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 3639-3642 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Conical intersections of the 2 2E′ and 1 2A1′ states of Li3 are considered as a first step in the description of the excited state involved in the absorption at 14 583 cm−1. Quite novel results are obtained. In addition to the standard symmetry-required D3h seam of conical intersection, C2v symmetry-allowed seams are found and their locus determined as a function the symmetric stretch coordinate. The C2v seams of conical intersection intersect the D3h conical intersection seam at two distinct points producing two heptafurcations of the D3h seam. The locus of the C2v conical intersection points is explained in terms of a quadratic Jahn–Teller model. The overall geometric phase effect associated with the D3h and C2v conical intersections is well described using a previously suggested phase factor deduced from molecular properties. In addition to these conical intersections an intersection of the 1 2A1′ and 2 2E′ is states is located. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478252
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  • 2
    Electronic Resource
    Electronic Resource
    Electronic structure aspects of the spin-forbidden reaction CH3(X 2A2″)+N(4S)→HCN(X 1Σ+)+H2(X 1Σg+) (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 4994-4999 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Second order configuration interaction wave functions based on molecular orbitals determined from a state-averaged multiconfigurational self-consistent field procedure are used to investigate the intermediate complex driven model for the spin-forbidden reaction CH3(X 2A2″)+N(4S)→HCN(X 1Σ+)+H2(X 1Σ+). The minimum energy crossing point (MECP), the minimum energy point on the surface of intersection connecting the reactant channel, 3A′′ potential energy surface, and product channel 1A′ potential energy surface, is determined directly, i.e., without a priori characterization of the individual potential energy surfaces. The MECP is found to be 8.2 kcal/mol below of the reactants. The structure at the MECP clearly evinces the incipient formation of a H2 bond. Barrierless paths from the reactants to the intermediate complex-methylnitrene, from the intermediate complex to the MECP, and from the MECP to the products are established. The absence of a barrier on these paths supports the intermediate complex mechanism. Spin–orbit interactions are determined to be ∼30 cm−1 for points on the surface of intersection in the vicinity of the MECP. Spin–orbit interactions and the local potential surface topology at the MECP are used to probe the efficiency of the intersystem crossing using the Landau–Zener model. A reduced dimensionality model is proposed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474862
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  • 3
    Electronic Resource
    Electronic Resource
    On the adiabatic to diabatic states transformation in the presence of a conical intersection: A most diabatic basis from the solution to a Poisson's equation. I (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 20-25 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the first determination of a "most" diabatic basis for a triatomic molecule based exclusively on ab initio derivative couplings that takes careful account of the limitations imposed by the nonremovable part of those couplings. Baer [Chem. Phys. Lett. 35, 112 (1975)] showed that an orthogonal transformation from adiabatic states to diabatic states cannot remove all the derivative coupling unless the curl of the derivative coupling vanishes. Subsequently, Mead and Truhlar [J. Chem. Phys. 77, 6090 (1982)] observed that this curl does not, in general, vanish so that some of the derivative coupling is nonremovable. This observation and the historical lack of efficient algorithms for the evaluation of the derivative coupling led to a variety of methods for determining approximate diabatic bases that avoid computation of the derivative couplings. These methods neglect an indeterminate portion of the derivative coupling. Mead and Truhlar also observed that near an avoided crossing of two states the rotation angle to a most diabatic basis, i.e., the basis in which the removable part of the derivative coupling has been transformed away, could be obtained from the solution of a Poisson's equation requiring only knowledge of the derivative couplings. Here a generalization of this result to the case of a conical intersection is used to determine a most diabatic basis for a section of the 1 1A′ and 2 1A′ potential energy surfaces of HeH2 that includes the minimum energy point on the seam of conical intersection. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476552
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  • 4
    Electronic Resource
    Electronic Resource
    Resonances in the predissociation of the A 2ΠΩ state of MgBr (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 4091-4101 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electronic structure methods and nonperturbative resonance theory are applied to study the radiative and radiationless decay mechanisms of the MgBr (A 2ΠΩ) vibrational levels. The X 2Σ+ and 1,2 2ΠΩ adiabatic electronic states are characterized using ab initio state-averaged multiconfigurational self-consistent field/second order configuration interaction wave functions. Interstate derivative couplings between the 2Π states have been calculated and used to construct a rigorous diabatic basis. The nonrelativistic potential energy curves are modified in the first order of degenerate perturbation theory to take account of the spin–orbit interactions treated within Breit–Pauli approximation. All vibrational levels in the A 2ΠΩ manifold are resonances predissociated by the repulsive 2 2Π state. A recently developed computational approach [S. Han and D. R. Yarkony, Mol. Phys. 88, 53 (1996)] based on a Feshbach formalism is employed to determine energies, linewidths, and radiative and radiationless decay rates in a coupled diabatic states basis within a Hund's case (a) approximation. Large nonadiabatic interactions cause significant energy shifts in the resonances levels. It is shown that a pronounced Ω-dependence in the radiationless decay rates results from the large fine structure splitting in the 2 2ΠΩ diabatic state which corresponds to Mg(1S)Br(2P). Comparisons with absorption and fluorescence spectra reveal important insights into A 2ΠΩ state decay. The spectroscopic constants of the A 2ΠΩ, Ω=3/2 and 1/2 states and the A 2Π3/2 state predissociation are well described in a Hund's case (a) approximation. However it is found that the A 2Π1/2 state predissociation is significantly underestimated in this limit. Rather the A 2Π1/2 state is indirectly predissociated by the 2 2Π3/2 state through rotational coupling to the A 2Π3/2 state. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473103
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  • 5
    Electronic Resource
    Electronic Resource
    Intramolecular Photoassociation and Photoinduced Charge Transfer in Bridged Diaryl Compounds.7.A Semiempirical MO Study of Intramolecular Charge Transfer in the Excited Singlet States of Dinaphthylamines (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 2018-2023 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100059a007
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  • 6
    Electronic Resource
    Electronic Resource
    Intramolecular Charge Transfer and Solvent-Polarity Dependence of Radiative Decay Rate in Photoexcited Dinaphthylamines (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 7416-7420 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100019a026
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