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  • Electronic Resource  (31)
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  • Electronic Resource  (31)
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  • 1
    Electronic Resource
    Electronic Resource
    Theory of dissociative charge exchange in ion-molecule collisions (1989)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 8128-8138 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100362a003
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  • 2
    Electronic Resource
    Electronic Resource
    Coupled wave packets study of the dynamics of dissociative ion–molecule charge exchange (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1020-1032 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A coupled wave packet method is presented which allows us to treat exactly the vibrational and dissociative motions in nonadiabatic atom–molecule collisions, whose relative motion is described by a classical trajectory. It consists of a time propagation of the coupled vibrational wave functions defined over a grid. It is applied to the dissociative charge exchange (DCE) process in atom–molecule collisions. Model cases are investigated that put forward the basic characteristics of the DCE process. Analysis of the time evolution of the wave packets leads to a direct view of the collision dynamics and to an interpretation of the dissociation mechanisms. Striking phenomena are revealed, that were not predictable by the previously existing approximate methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461181
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  • 3
    Electronic Resource
    Electronic Resource
    A comparison of approximate techniques for the determination of potential energy surfaces of ion–molecule charge transfer systems (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 6579-6587 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The (HO2)+ molecular ion is used to experiment two approximate procedures which aim at reducing the computation effort that is needed for the determination of potential energy surfaces of ion–molecule charge transfer systems. The two procedures involve configuration interaction (CI) calculations of moderate sizes and are based on diagonal corrections of the electronic Hamiltonian matrix in a basis of projected-valence bond (PVB) configuration-state functions (CSF). The PVB-CSF's used in practice correspond to a full valence CI for each ionic or neutral partner as well as single excitations accounting for polarization and electron transfer. The diagonal corrections are of two sorts: (i) if insufficiently large orbital expansion bases are used they remove the relative ion–molecule basis set superposition error; (ii) if asymptotic energy levels of the involved neutrals or ions in their ground or valence excited states are misplaced they properly adjust these levels. When applied to (HO2)+ using a minimal or an extended orbital basis set expansion the proposed approaches yield concording results. The results also agree with the effective model potential (EMP) data of Grimbert et al. [Chem. Phys. 124, 187 (1988)] which have proved successful in the description of the H++O2 charge transfer dynamics. Comparison with fragmentary results from MRD-CI calculations by Vazquez et al. [Mol. Phys. 59, 291 (1986)] and Schneider et al. [Chem. Phys. 128, 311 (1988)] is somewhat mitigated. The method should be particularly useful for bulky ion–molecule systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463661
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  • 4
    Electronic Resource
    Electronic Resource
    A new formula for determining differential cross sections in the vibronic semiclassical description of atom–molecule collisions (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 7530-7531 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A simple approximation applied to the eikonal expression of the scattering amplitude provides a new formula for the determination of differential cross sections for atom–molecule collisions described within the vibronic semiclassical framework. The derived formula achieves considerable savings in the corresponding numerical work and extends the well-known expansion over Legendre polynomials to nonspherical interactions. Results obtained with the new formula on vibrational excitation and vibronic charge exchange in the H++O2 collision at Ecm=23 eV are found to be in excellent agreement with the calculations of Sizun et al. (J. Phys. Chem. Lett.).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459383
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  • 5
    Electronic Resource
    Electronic Resource
    Vibrational state-to-state calculations of H++O2 charge transfer collisions (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 307-325 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A comprehensive theoretical investigation of vibrational excitation and vibronic charge transfer in the H++O2 collision at ECM=23 eV is reported. The calculations of differential and integral scattering observables are undertaken within both the quantal infinite order sudden (QIOS) and the vibronic semiclassical (VSC) approximations. They involve 2×15 vibronic expansions associated with the diabatic states determined by Grimbert et al. [Chem. Phys. 124, 187 (1988)] using a so-called effective model potential (EMP) method. A quadripartite comparison involving experimental data of Noll and Toennies [J. Chem. Phys. 85, 3313 (1986)], results of a QIOS treatment of Gianturco et al. [Phys. Rev. A 42, 3926 (1990)] based on DIM potentials and the present QIOS, and VSC results is presented. From the comparison of the theoretical and experimental results we find that the present calculations based on the EMP reproduce much better the experimental data than those based on the DIM potentials. Though differences are found between the present QIOS and VSC results, the experimental data do not help deciding between the two theories. The relative merits of the QIOS and VSC approaches are put forward and discussed. By scrutinizing intermediate results of lengthy calculations we have been able to bring out elementary models in them. Pure vibrational excitation is found to be a prominent process in this system and charge transfer substantially affects it.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462519
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  • 6
    Electronic Resource
    Electronic Resource
    Theoretical investigation of differential cross sections for vibrational excitation and vibronic charge transfer in H++H2 collisions (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7277-7278 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The multitrajectory semiclassical method combined with the fixed rotor approximation is used to investigate the differential state-to-state scattering in H++H2 collisions at Ec.m.=20 eV. Little differences are found with respect to previous quantal infinite order calculations of Baer et al. [J. Chem. Phys. 91, 4169 (1989)] when similar DIM (diatomics in molecules) potential energy surfaces are used. Adjustment of the ground state DIM potential energy surface to ab initio data considerably improves the comparison with the experiment of Niedner et al. [J. Chem. Phys. 87, 2685 (1987)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465416
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  • 7
    Electronic Resource
    Electronic Resource
    Ground and excited state adiabatic 2A″ and 2A′ potential energy surfaces of the (Kr–O2)+ cluster ion (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 191-199 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The seven lowest adiabatic potential energy surfaces (PES) of the (Kr–O2)+ cluster ion in each of the 2A″ and 2A′ symmetries are calculated. The computational method involves configuration interaction calculations in a basis of a thousand projected valence-bond state functions. It resorts to diagonal corrections of the Hamiltonian matrix prior to configuration interaction and makes use of an l-dependent pseudopotential for Kr. The results are characterized by the shallowness of the 1 2A″ potential well and the absence of wells in the other PES investigated. The 1 2A″ equilibrium characteristics differ significantly from those proposed in other work. Notable effects on all the PES are observed when the O–O bond is stretched beyond 2.5a0. No 1 2A′−2 2A′ (nor 1 2A″−2 2A″) pseudocrossings are found that could explain, on the basis of mere electronic structure arguments, the available thermal energy charge transfer data. A 2 2A″−1 2A′ crossing actually exists but the related Coriolis coupling mechanism cannot be invoked for low energy 〈1 eV encounters. This draws attention to alternative more subtle dynamic charge transfer mechanisms possibly involving quartet-doublet spin–orbit transitions and/or (near) degeneracies of rovibronic, instead of mere electronic, energy levels. Evidence is shown for pseudocrossing mechanisms of population sharing between the 2,3A″ and 2A′ states. Similar evidence is shown for an O2(X 3Σ−g)→O2(a 1Δg) excitation involving two electron rearrangement. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470888
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  • 8
    Electronic Resource
    Electronic Resource
    2Σ+ potential energy curves of the (Na19–Na)+ jellium-cluster-ion system (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 1288-1294 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A prototypical description of the (Na19–Na)+ system is reported. The Na atom, in its ground and first two excited states, is treated by a one-electron pseudopotential method. The cluster is first described in the spherical jellium background model (SBJM). A numerical Hartree–Fock approach is used to calculate the electronic wave function of the cluster in its ground state configuration. Singly excited Na19* states are obtained using an improved virtual orbital technique to allow for the distortions of the cluster electron cloud during the Na19–Na approach. The matrix of the electronic Hamiltonian in a (diabatic) basis of projected valence bond configuration state functions are determined with an effective model potential method. As a first model case, the (Na19–Na)+ system is treated holding the isolated positive background of the jellium cluster unchanged. This description pertains to rapid displacements of the atom relative to the cluster. As a second case, we consider distortion and reconstruction of the positive background as the Na+-ion core approaches and penetrates into the cluster core. The latter description is appropriate for slow displacements of the atom relative to the cluster. Potential energy curves are reported for the 2Σ+ states. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468917
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  • 9
    Electronic Resource
    Electronic Resource
    Semiclassical coupled wave packet study of the nonadiabatic collisions Ar+(J)+H2: Zero angular momentum case (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 4530-4543 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The title reaction is investigated for total angular momentum I=0 using a semiclassical coupled wave packet method where the Smith–Whitten-type hyperspherical angles θ and cursive-phi are treated quantally, and the hyperspherical radius ρ is treated classically. The wave function is expanded over an electronic basis set which includes 28 states. The diabatic potential energy surfaces are determined by DIMZO calculations. Probabilities for reaction, charge transfer, collision induced dissociation, dissociative charge transfer, and fine structure transitions are obtained in the energy range 0.3 eV≤E≤30 eV. A comprehensive analysis of the reaction mechanisms is presented. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471156
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  • 10
    Electronic Resource
    Electronic Resource
    Vibronic semiclassical calculations of differential cross sections for excitation and charge transfer in hydrogen(1+) + oxygen collisions (1990)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 94 (1990), S. 5674-5676 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100378a015
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