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  • 1
    Electronic Resource
    Electronic Resource
    A multisurface DIM trajectory study of the reaction: O(1Dg)+H2(X 1Σ+g)→OH(X 2Π)+H(2S) (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3629-3637 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The diatomics-in-molecules method has been used to compute potential energy surfaces for the interactions between O(1Dg) atoms and hydrogen molecules, and a multisurface quasiclassical trajectory study of the reaction dynamics for collisions at several different reagent translational energies has been carried out using these potentials. The multisurface nature of the problem was explicitly included by using a surface-hopping computational technique, based on Landau–Zener transition probabilities, which made all of the relevant surfaces available to the trajectory. The product energy distributions predicted by three slightly different DIM models of these surfaces are computed. In all cases, the dynamics of the reactions which begin on the first excited surface are dramatically different from those of reactions which occur on the lowest surface, the only one which was considered in all previous dynamical calculations on this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453913
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  • 2
    Electronic Resource
    Electronic Resource
    Diatomics-in-molecules models for H2O and H2O−. II. A self-consistent description of the 1A′, 1A″, 3A′, and 3A″ states of H2O (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 2863-2874 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper describes a small (6 to 9 basis functions) model for the potential energy surfaces relevant to the chemical reaction O(1D)+H2→OH(X 2Π)+H. The model is optimized with respect to the 1A′ and 1A″ states correlating with the reagents and products of this reaction; this is done in such a way as to simultaneously provide a qualitatively correct description of the 3A′ and 3A″ states of H2O. In this sense the model is self-consistent. In agreement with other semiempirical work, the results indicate that two 1A′ surfaces and one 1A″ surface are pertinent for a dynamical study of this reaction. The model adequately represents the most important features of H2O potential energy surfaces and is at the same time small enough to be used directly in a trajectory calculation of the reaction cross section.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453074
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  • 3
    Electronic Resource
    Electronic Resource
    Diatomics-in-molecules models for H2O and H2O−. I. Valence bond diatomic fragment matrices (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 2352-2364 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Valence bond wave functions for the ground states OH(X 2Π) and OH−(X 2Σ+) were analyzed in order to arrive at DIM models for those states of H2O and H2O− correlating with the ground states of the separated atoms. The models are meant to provide a framework for studying the negative ion reaction O−+H2 → OH−+H and to test the utility of DIM in describing at a simple level the bonding in the water molecule. Projection analysis of the ab initio wave functions shows that in addition to the VB structures arising from the coupling of ground state atoms, ionic structures are important, especially for H2O, but that structures with excited states of H can be neglected. Within the space of the DIM model basis functions, diatomic fragment matrices were computed by the VB method to produce library files for eight state manifolds of OH−, six manifolds of OH, two manifolds of OH−−, and four manifolds of H−2. These will be useful as input for future DIM calculations on molecules containing O–H bonds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448331
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of reagent excitation on the dynamics of the reaction O(1D2)+H2→OH(X 2Π)+H (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 8038-8047 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effect of H2 translational, rotational, and vibrational excitation on the dynamics of the O(1D2)/H2 reaction are explored in a semiclassical trajectory study involving both of the energetically accessible potential energy surfaces of the system. Landau–Zener probabilities determine surface hopping. At low reagent excitation, the deep H2O potential minimum dominates the dynamics, causing the reagents to reorient towards a H–O–H (insertion) configuration and form the H2O intermediate, irrespective of the initial approach geometry. High vibrational excitation enhances the probability for transitions onto the excited state potential during the interaction. Reactions which sample the excited state potential have fundamentally different dynamics from those which remain on the lower state. For reactions involving H2(v=4), the OH product has a bimodal vibrational distribution, peaking in OH(v'=2) and OH(v'=9). The lower peak is due to reactions which access the excited state potential; the higher peak results from those which remain on the lower state for the entire interaction. High translational excitation shortens the interaction time and reduces the effect of the potential minimum to reorient the reagents. Rotational excitation also reduces the effect of the potential minimum by causing the system to rotate out of the insertion geometry before entering the potential minimum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461284
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  • 5
    Electronic Resource
    Electronic Resource
    Classical path surface-hopping dynamics. II. Application to Ar+3 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 156-165 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A classical path surface-hopping trajectory approach is applied to the study of the dissociation of singly charged argon trimer-ions produced in the ionization process Ar3→Ar+3→Ar+2+Ar. Production of the ions in each of the first three adiabatic states is investigated with a view to describing the dynamics of the newly produced ion from its formation up to the time it dissociates. In the ground state, the motion typically involves several sequences of a vibration of the charged pair in a dimer subsystem Ar+2, followed by charge transfer to form a different dimer subsystem. In the second and third states, there is concerted motion until passage of a nonadiabatic region leads to a transition to the ground state, from whence dissociation occurs via a sequence of pair collisions. In the third state, the motion is more erratic, the charge being delocalized a large fraction of the time. The different dynamical mechanisms are interpreted in terms of charge migration and nonadiabatic effects. A few trajectories for Ar+n for n=3, 4, and 5 exhibit similar charge migration behavior, suggesting the applicability of these dissociation mechanisms to small clusters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461471
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  • 6
    Electronic Resource
    Electronic Resource
    Classical path surface-hopping dynamics. I. General theory and illustrative trajectories (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 141-155 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A formulation of a trajectory surface-hopping method is presented which starts with some of the basic ideas of the standard method, extends these to include more than two states, and enlists the classical-path equations not only to propagate through the nonadiabatic region but also to effect the transitions, or surface hops, themselves. The latter is accomplished by letting the Hamiltonian matrix elements in the time-dependent Schrödinger equation become complex, allowing manipulation of the fluctuation in the various adiabatic state populations. The procedure automatically conserves total energy and angular momentum as well as probability, and ensures that energetically inaccessible states are not significantly populated. In regions of extended degeneracy, the method resembles the standard classical-path approach with no surface hopping. In fact, the evolution of the wave function can be controlled to behave either as in the surface-hopping extreme or in the pure semiclassical extreme, allowing the method to be tailored to suit individual systems. The procedure is illustrated by application to a well-studied collision induced predissociation, Ne+He+2→Ne++He+He, where vibration in the entrance channel, Ne+He+2, leads to the strong nonadiabatic behavior responsible for the large observed cross sections. A few preliminary calculations for singly charged argon trimer ions produced in the ionization process Arn→Ar+n→Ar+2+(n−2)Ar, demonstrate that the formulation can be easily extended to include many degrees of freedom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461470
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  • 7
    Electronic Resource
    Electronic Resource
    A diatomics-in-molecules model for the 1A' potential energy surfaces of H2Cl+ (1991)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 8364-8370 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100174a059
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  • 8
    Electronic Resource
    Electronic Resource
    Conical intersections in H2Cl+(1A') (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5149-5158 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A 10×10 model Hamiltonian matrix for the 1A' states of the H2Cl+ molecule in a valence-bond basis is shown to exhibit conical intersections between states 2 and 3 along a line in configuration space (linea diaboli). The points of intersection are located by finding the minimum in the square of the difference of the two eigenvalues and then confirming the nature of the intersection by calculation of the geometrical phase associated with transporting an eigenvector about the point. The locus of the linea diaboli does not correspond to any obvious special geometrical symmetry but rather appears to be related to the charge distributions in the molecular states correlating with the H+HCl+ (A 2Σ+ ) and H+ +HCl(X 1Σ+) asymptotic channels. Some properties of the degenerate eigenstates at the intersections are presented and it is shown how the approximate geometric configurations of the intersection can be found from the eigenvectors of the two appropriate states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461683
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  • 9
    Electronic Resource
    Electronic Resource
    Erratum: The effect of reagent excitation on the dynamics of the reaction O(1D2)+H2→OH(X 2P)+H [J. Chem. Phys. 95, 8038 (1991)] (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 6324-6324 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462910
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  • 10
    Electronic Resource
    Electronic Resource
    Unified large basis set diatomics-in-molecules models for ground and excited states of H3 (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 822-832 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A recently developed systematic diatomics-in-molecules (DIM) procedure has been applied to the system H+H2 in order to generate large basis set models capable of approximating both the ground and low-lying excited state potential energy surfaces in a unified manner. The procedure, based exclusively on an analysis of diatomic ab initio wave functions, suggests that a 20-structure model including structures with not more than one excited H atom (2s or 2p) should suffice for the H3 (2A') states. An 80-structure model including up to two excited H atoms yielded potential energy surfaces in close agreement with the smaller model. The ground state surface shows a greatly improved behavior in D3h configurations when compared to the simplest, two-structure DIM model for H3 but is otherwise very similar to that surface. This result exemplifies the stability of our systematic DIM methodology to increases in the size of the basis set. A number of excited state surfaces, including the lower 2A‘ and quartet states, are reported and the implications for reaction kinetics are discussed. In particular, we predict the reaction H*(2s or 2p)+H2→H+H+H to have a large cross section.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450582
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