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  • 1
    Digitale Medien
    Digitale Medien
    A wave packet Golden Rule treatment of vibrational predissociation (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 4230-4233 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The time-dependent wave packet technique is applied to the Golden Rule treatment of vibrational predissociation. The wave packet at time zero is taken as the product of the quasibound wave function and the coupling inducing predissociation. The rate for vibrational predissociation can then be obtained by Fourier transform into the energy domain of the time-dependent wave packet autocorrelation function. The method has been applied to a model triatomic van der Waals molecule. It is shown that when the bound-state components of the wave packet are projected out, the time-dependent version of the Golden Rule approximation provides an alternative efficient technique to treat intramolecular decay.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.460631
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  • 2
    Digitale Medien
    Digitale Medien
    Double continuum fragmentation in the vibrational predissociation X⋅⋅⋅BC(v)⋅⋅⋅Y→BC(v'〈v)+X+Y of van der Waals complexes: A perturbative treatment (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4016-4023 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We present an approximate quantal model to study the double continuum problem arising in the complete fragmentation of X⋅⋅⋅BC(v)⋅⋅⋅Y van der Waals(vdW) complexes, where BC is a conventional diatomic molecule vibrationally excited and X and Y are rare gas atoms, through vibrational predissociation (VP). Assuming a near equilibrium geometry of the complex and using an adiabatic approximation for describing the oscillation in the angle formed by the BC⋅⋅⋅X and BC⋅⋅⋅Y weak bonds, the rates for complete fragmentation are expressed in the frame of Fermi's "Golden Rule''. Double continuum wave functions may be obtained by a perturbative treatment that allows one to take properly into account the symmetry of the problem in the particular and very frequent case X≡Y.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.458786
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  • 3
    Digitale Medien
    Digitale Medien
    Photofragmentation of the Ne⋅⋅⋅ICl complex: A three-dimensional quantum mechanical study (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 3348-3358 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Converged three-dimensional quantum mechanical calculations for photofragmentation of the Ne⋅⋅ICl van der Waals molecule in the energy region of the electronically excited B(3∏0+) state of ICl are presented and compared with experiments. Lifetimes and final state distributions for the ICl fragments were determined for vibrational predissociation from the lowest van der Waals level in the B(v'=2) channel. Good agreement between theory and experiment was achieved using a sum of atom–atom pairwise potentials. This potential energy surface predicts the equilibrium geometry of the complex to be bent at 140° with the Ne atom towards the Cl end of ICl. The diabatic vibrational golden rule (DVGR) approximation, as well as the rotational infinite order sudden approximation (RIOSA), have been tested again the full 3D calculations. Analysis of the quasibound wave function reveals that the highly inverted rotational distribution of the ICl fragments observed in the experiment, is not due to zero-point bending motion. It is more likely to be due to a rotational rainbow effect enhanced by the favorable initial geometry of the complex. The effect of the excitation of the bending van der Waals mode in the complex has also been studied. As compared with the lowest level, a longer lifetime and a different rotational distribution of the fragments is predicted. The results presented in this work not only elucidates many dynamical aspects of vibrational predissociation for the Ne⋅⋅⋅ICl complex, but also provide benchmark data for the study of other theoretical methods and approximations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.458578
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  • 4
    Digitale Medien
    Digitale Medien
    On the coupling of rotovibrational motions in He–Li2 inelastic collisions (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 5024-5035 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: He–Li2 interaction potentials, which explicitly include both angular anisotropy and internal vibrational coordinates, have been proposed recently in the literature by extracting them from laser-selected, crossed beam experiments and from the use of various perturbation expansions. In view of the importance of assessing as accurately as possible the dynamical coupling of such internal degrees of freedom during inelastic, low-energy collisions, the present study undertakes a detailed computational comparison of the various possible decoupling schemes which can be employed to treat the above processes. It is found that because of the rather weak nature of the interaction in the title system, nearly all schemes work reasonably well and can be used in scattering calculations. It is, however, shown that the previously suggested potentials need to be modified extensively in order to yield cross sections which agree with the experimental findings.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.461690
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  • 5
    Digitale Medien
    Digitale Medien
    Dissociation dynamics of I2⋅⋅⋅Nen van der Waals clusters (n=1–9): A quasiclassical approach (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7868-7874 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The dynamics of vibrational predissociation (VP) of van der Waals (vdW) I2⋅⋅⋅Nen clusters is studied by means of a quasiclassical trajectory approach. We assume a near-equilibrium geometry that accounts for the I2 stretch and the stretching and bending modes of the rare gas atoms restricted to move along a plane perpendicular to the I2 axis. A sharp increase of the halfwidth is observed for n=9 together with certain stability of the n=8 cluster size with respect to dissociation. It would indicate the existence of a first coordination shell for Ne around I2 containing eight atoms. In addition, the dissociation results less and less efficient as n increases and statistical mechanisms become important for the cluster sizes studied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.460122
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  • 6
    Digitale Medien
    Digitale Medien
    Structure and dynamics of small I2 . . . Hen van der Waals clusters (n=1–9) (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 6504-6513 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Energetics and dynamics of van der Waals (vdW) I2⋅⋅⋅Hen clusters are studied in an approximate way by using a model that considers 2n+1 degrees of freedom, that is, the I2 stretch and the 2n stretching and bending modes of the He atoms restricted to move along a plane perpendicular to the I2 axis. For n=2,3 a configuration-interaction treatment is carried out to obtain energy levels. For n=4–8, ground-level energies are estimated from those corresponding to n=2,3 and the geometric relationships among the n vdW bonds. A quasiclassical trajectory approach is used to study the dynamics of these clusters, and lifetimes and half-widths for vibrational predissociation have been calculated for n=1–9. A large increase in the half-width of n=9 with respect to the cases n=1–8 is observed, which would imply the existence of a first coordination shell for He about I2 containing eight atoms. Also, it is found that the mechanisms of dissociation for these clusters become statistical as the number of vdW bonds increases.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.458285
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  • 7
    Digitale Medien
    Digitale Medien
    Study of the diffraction mediated selective adsorption through the close-coupling and diabatic distorted wave formalisms. Application to the 4He–Cu(110) system (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 3823-3830 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Two different formalisms, one based on close-coupling equations and other on the distorted wave approximation, have been applied to the low energy elastic scattering of 4He atoms by a corrugated copper surface, Cu(110). Diffraction intensities and energetic positions and half-widths (selective adsorption resonances) have been obtained and compared with experimental and previous theoretical results, respectively. For this trapping process, and within the close-coupling framework, a plot of the diffraction channels (open and closed) has turned out to be very useful and a good guide in order to know the disposition of them at each interesting angular region. Also, a very accurate method, already employed successfully to treat resonances in the vibrational and/or rotational predissociation of van der Waals molecules, has been found to be also adequate here.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.455839
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  • 8
    Digitale Medien
    Digitale Medien
    An approximate quantal treatment to obtain the energy levels of tetra-atomic X ⋅⋅⋅ I2 ⋅⋅⋅ Y van der Waals clusters (X,Y=He,Ne) (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 496-507 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The structure of tetra-atomic X ⋅⋅⋅ I2 ⋅⋅⋅ Y van der Waals (vdW) clusters, where X,Y=He,Ne, is studied using an approximate quantal treatment. In this model the above complexes are treated as like diatomic molecules with the rare-gas atoms playing the role of electrons in conventional diatomics. Then a H2-like molecular-orbital formalism is applied, choosing the discrete states of triatomic systems I2 ⋅⋅⋅ X(Y) as molecular orbitals. Calculations at fixed configurations as well as including vdW bending motions restricted to the plane perpendicular to the I2 axis have been carried out for the sake of comparison with previous results. Finally, the restrictions are relaxed and the vdW bending motions are incorporated in a full way within the framework of a configuration interaction. The structure of these clusters is also studied through the probability density function.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.458451
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  • 9
    Digitale Medien
    Digitale Medien
    Study of the electronic-to-vibrational energy transfer in the quenching process of Na*(3 2P) with N2(1Σ+g,v=0). A quantal close coupling calculation (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 155-161 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Electronic-to-vibrational energy transfer has been studied by solving numerically the close-coupling equations, in the T-shape configuration, on the two lowest electronic states of the Na–N2 system. The diabatic potential surfaces were taken from Archirel and Habitz while the interelectronic coupling was modeled by different Gaussian-type functions. Different sets of parameters for the coupling were used in order to study the final vibrational distributions of N2. Finally, partial quenching probabilities are presented and compared with previous theoretical and experimental works.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457494
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  • 10
    Digitale Medien
    Digitale Medien
    Competitive internal transfers in metastable decay of cluster ions (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6472-6486 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: In a previous study of fragmentation patterns of (Ar)+3 clusters [G. Delgado-Barrio, S. Miret-Artés, P. Villarreal, and F. A. Gianturco, Z. Phys. D 27, 354 (1993)] it was found that overall rotations control the lifetimes of the occupied metastable states of the cluster and that a spherical, effective interaction was sufficient to describe the dynamical process. In the present study, the strong anisotropy of a more realistic three-particle interaction is introduced and its effects on metastable decay are examined. By separating internal rotations from internal vibrations of the diatomic ion, it is possible to show that internal predissociation pathways are very efficient and lead to very short lifetimes. The latter can be lengthened only when overall rotational states are directly included, thus confirming the physical picture of the earlier work.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.467056
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