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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Erratum: Angular momentum dependent barriers: Possible key to understanding angular distributions for the reactions of fluorine with H2, D2, and HD [J. Chem. Phys. 89, 5598 (1988)] (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 622-622 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457687
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  • 3
    Electronic Resource
    Electronic Resource
    Angular momentum dependent barriers: Possible key to understanding angular distributions for the reactions of fluorine with H2, D2, and HD (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5598-5606 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The bending corrected rotating linear model is used to study the angular distributions for the reactions F+H2, F+HD, and F+D2. The calculations are performed using two new surfaces (No. T5 and T5A) that were recently reported by Steckler et al. (Ref. 3). Analysis of the factors determining the shapes of these angular distributions indicates that the angular momentum dependence of the vibrationally adiabatic barriers in the entrance and exit channels plays a central role in determining the characteristics of the vibrational state-selected, reactive product angular distributions. While the distributions predicted for the reactions F+H2(v=0)→H+HF(v'=3), F+D2(v=0)→H=DF(v'=4), and F+DH(v=0)→H+DF(v'=4) are in good agreement with the high resolution molecular beam studies of these same reactions, the angular distributions predicted for the reaction F+HD(v=0)→D+HF(v'=3) do now show the forward scattering of products derived from high resolution molecular beam studies. This discrepancy appears to be due to a shortcoming in the T5 and T5a surfaces (i.e., the angular momentum dependent, vibrationally adiabatic barriers in the exit channel are too high in energy to permit forward "resonant'' scattering at the low scattering energies corresponding to the experimental studies).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455566
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  • 4
    Electronic Resource
    Electronic Resource
    Prediction of angular distributions for the F+H2 and F+D2 reactions (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5978-5979 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The bending corrected rotating linear model is used to predict angular distributions for the reactions F+H2(v=0)→H+HF(v'=2,3) and and F+D2(v=0)→D+DF(v'=3,4). The calculations were performed using the surface (No. 5A) that was reported recently by Steckler, Truhlar, and Garrett. The angular distributions obtained using this new surface differ in several important respects from distributions predicted in earlier quantal scattering studies using the Muckerman-5 surface. More importantly, these new predictions are in much better agreement with the high resolution molecular beam studies of these same reactions. The combination of these predictions with the results of the molecular beam studies provides additional evidence for the role of dynamical resonances in the two title reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454513
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  • 5
    Electronic Resource
    Electronic Resource
    Erratum: "Three-body collision contributions to recombination and collision-induced dissociation. II. Kinetics" [J. Chem. Phys. 109, 6714 (1998)] (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 1668-1669 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A programming error, which affects many of the numbers, tables, and figures of this paper, is corrected. It does not affect any of the conclusions of the work. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481957
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  • 6
    Electronic Resource
    Electronic Resource
    Quantum scattering studies of long-lived resonances for the reaction Ne+H+2→NeH++H (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 2728-2742 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The bending-corrected rotating linear model (BCRLM) is used to investigate the reaction of neon with H+2 (v=0–3) using three different fits to the ab initio potential-energy surface computed by Urban, Jaquet, and Staemmler. Numerous long-lived scattering resonances are found for each surface. The number and position of these scattering resonances are found to be sensitive to the relatively small differences among these three surfaces. These BCRLM results demonstrate how the rich resonance structure that appears in the partial cross sections is washed out in the total cross section. The integrated rates for reactivity from v=0 and 1 are nearly identical for all three potential-energy surfaces over a wide range of temperatures. However, the integrated rates from v=2 and 3 exhibit significant differences among the potential-energy surfaces. A vibrationally adiabatic hyperspherical model of the trapped resonance states provides insight into the nature and contribution of these resonances to reactive scattering. The more accurate of the three fits to the ab initio potential-energy surface (obtained using the functional form of Aguado and Paniagua) is also used to obtain converged results for total angular momentum J=0 employing the adiabatically adjusting, principal axis, hyperspherical (APH) formulation of Pack and Parker for quantum reactive scattering in three dimensions (3D). An eigenlifetime analysis of these 3D scattering results reveals numerous resonances with lifetimes of 1 ps or more. While this resonance structure is sensitive to the details of the potential energy surface, with appropriate Gaussian averaging over the total scattering energy, the cumulative reaction probabilities (CRPs) are not very sensitive to changes in the potential energy surface. Moreover, these quantum CRPs agree rather well with CRPs predicted using variational Rice–Ramsperger–Kassel–Marcus (RRKM) calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466467
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  • 7
    Electronic Resource
    Electronic Resource
    Reactive differential cross sections in the rotating linear model. Reactions of fluorine atoms with hydrogen molecules and their isotopic variants (1984)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 88 (1984), S. 3318-3325 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j150659a036
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  • 8
    Electronic Resource
    Electronic Resource
    Three-body collision contributions to recombination and collision-induced dissociation. II. Kinetics (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6714-6724 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Detailed rate constants for the reaction Ne+Ne+H(r harp over l)Ne2+H are generated, and the master equations governing collision-induced dissociation (CID) and recombination are accurately solved numerically. The temperature and pressure dependence are explored. At all pressures, three-body (3B) collisions dominate. The sequential two-body energy transfer (ET) mechanism gives a rate that is more than a factor of two too small at low pressures and orders of magnitude too small at high pressures. Simpler models are explored; to describe the kinetics they must include direct 3B rates connecting the continuum to the bound states and to the quasibound states. The relevance of the present reaction to more general CID/recombination reactions is discussed. For atomic fragments, the 3B mechanism usually dominates. For diatomic fragments, the 3B and ET mechanism are competitive, and for polyatomic fragments the ET mechanism usually dominates. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477349
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  • 9
    Electronic Resource
    Electronic Resource
    Hyperspherical surface functions for nonzero total angular momentum. I. Eckart singularities (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 6673-6693 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new hybrid numerical technique which utilizes both the DVR (Discrete Variable Representation) and FBR (Finite Basis Representation) to solve for the full 5D surface functions in the three-atom problem in hyperspherical coordinates for nonzero total angular momentum (J≠0) is reported. This method accurately treats the Eckart singularities in the kinetic energy operator which occur at both the north pole and equator of the 2D hypersphere in body-frame coordinates. The effects of the Eckart singularities on the surface function energies for HD2 are investigated and it is shown that an accurate treatment of these singularities is crucial in order to obtain the correct results. An improper treatment of the Eckart singularities could be a source for some of the discrepancies between recent experimental results and theory for the reaction H+D2→HD+D. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478574
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  • 10
    Electronic Resource
    Electronic Resource
    Three-body collision contributions to recombination and collision-induced dissociation. I. Cross sections (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6701-6713 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Many of the current chemical kinetics textbooks and kinetics papers treat atomic and molecular recombination and collision-induced dissociation (CID) as occurring only via sequences of two-body collisions. Actually, there is considerable evidence from experiment and classical trajectory calculations for contributions by true three-body collisions to the recombination of atomic and diatomic radicals, and that evidence is reviewed. Then, an approximate quantum method treating both two-body and three-body collisions simultaneously and on equal footing is used to calculate cross sections for the reaction Ne2+H(r harp over l)Ne+Ne+H. The results provide clear quantum evidence that direct three-body collisions do contribute significantly to recombination and CID. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477348
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