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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 89 (1985), S. 2612-2620 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8073-8080 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction of electronically excited Na(2P) with HCl to produce NaCl and H has been studied using a quasiclassical surface hopping trajectory program. Two translational energies (5.6 and 16.3 kcal/mol) and two HCl vibrational states (v=0 and 1) were investigated. We find that the reaction cross section increases with vibrational excitation and decreases with increasing translational energy. The calculated reaction cross section of 3.02±0.25 A(ring)2 at 5.6 kcal/mol and v=0 agrees with the results of recent molecular-beam experiments on this system. The ground and first excited state potential-energy surfaces and the nonadiabatic coupling between these surfaces were calculated using the diatomic-in-molecules (DIM) method. Reactive trajectories which occur on these surfaces remain in the interaction region for nearly 1 ps and must pass through a perpendicular geometry. This critical geometry corresponds to the avoided crossing seam region.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6713-6718 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The collision induced dissociation (CID) and charge transfer (CT) cross sections have been determined for H+2 and D+2 colliding with H2 using a surface hopping trajectory method. Approximately 40 000 trajectories have been analyzed for collisions at 4.0, 6.0, and 8.0 eV (center of mass) and for H+2 (D+2 ) in vibrational states from 0 to 10. Our results are consistent with the recent experiments of Guyon, Baer, Cole, and Govers [Chem. Phys. 119, 145 (1988)]. However we have come to a different understanding of the mechanism for dissociation. We find that there are two pathways for CID: (1) formation of a H+3 intermediate followed by dissociation and (2) direct dissociation of a H+4 transition state via vibrational excitation. The H+3 intermediate pathway predominates at low collisional and low H+2 (D+2 ) vibrational energies.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 105-111 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper describes a new fast Fourier transform technique to determine the transformations from action-angle variables to Cartesian coordinates for a rotating diatomic molecule. This allows one to obtain the initial values of the coordinates and momenta for a given v and J from properly weighted radial and angular distributions as required in quasiclassical trajectory calculations. This method offers a number of advantages over previous methods for obtaining initial values. It is very accurate, even for cases of high J. This method works equally well for all types of diatomic potentials. Results are reported for Morse potentials and extended Rydberg potentials.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 6984-6992 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper describes the use of an exact fast Fourier transform method to prepare specified vibrational–rotational states of triatomic molecules. The method determines the Fourier coefficients needed to describe the coordinates and momenta of a vibrating–rotating triatomic molecule. Once the Fourier coefficients of a particular state are determined, it is possible to easily generate as many random sets of initial Cartesian coordinates and momenta as desired. All the members of each set will correspond to the particular vibrational–rotational state selected. For example, in the case of the ground vibrational state of a nonrotating water molecule, the calculated actions of 100 sets of initial conditions produced actions within 0.001(h-dash-bar) of the specified quantization values and energies within 5 cm−1 of the semiclassical eigenvalue. The numerical procedure is straightforward for states in which all the fundamental frequencies are independent. However, for states for which the fundamental frequencies become commensurate (resonance states), there are additional complications. In these cases it is necessary to determine a new set of "fundamental'' frequencies and to modify the quantization conditions. Once these adjustments are made, good results are obtained for resonance states. The major problems are in labeling the large number of Fourier coefficients and the presence of regions of chaotic motion. Results are presented for the vibrational states of H2O and HCN and the rovibrational states of H2O. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 92 (1988), S. 3858-3863 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 96 (1974), S. 4084-4089 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 5317-5324 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper presents the detailed results of a quasiclassical trajectory surface hopping study of reaction of highly vibrationally excited H+2 with ground state H2 (and isotopic counterparts H+2 +D2, D+2 +H2, and D+2 +D2 ), with particular emphasis on the formation and decay of metastable H+3 products. A diatomics-in-molecules surface is used which has been successful in previous studies of H+2 (v) + H2 at low v. In the present study, we consider v=0–17, and find that metastable H+3 's are a major product for v≥13. Some of these metastables decay rapidly, showing exponential lifetime distributions with 2–7 ps lifetimes depending on v and on isotope. The remaining H+3 's have much longer lifetimes, and a number of methods are used to determine the origin of their stability. In no cases are any of these molecules found to be quasiperiodic, but a Fourier spectral analysis reveals some decoupling of H+ –H2 orbital motion from H2 rotational motion, and we find that many molecules have long lifetimes even though they have energies which are above any rigorous centrifugal barrier. The relation of these results to recent infrared absorption measurements on highly excited H+3 's is discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 4532-4539 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Trajectory surface hopping calculations were performed on optimized diatomics-in-molecules surfaces to study Na(2P) collisions with H2 and D2 molecules (v=0, j=1) at four different translational energies (0.039, 0.062, 0.101, and 0.140 eV). Two methods were used to predict surface hopping: (1) transformation of the multidimensional surface intersection to a local one-dimensional curve crossing and calculation of the Landau–Zener transition probability, and (2) integration of the coefficients of the adiabatic electronic states to determine transition probability. For all initial conditions used in this work, we found that method (2) gave significantly larger quenching cross sections. Also in this paper we present results that show nonadiabatic coupling terms calculated by the diatomics-in-molecules method are in good agreement with ab initio values.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The chemical educator 5 (2000), S. 329-334 
    ISSN: 1430-4171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pH titration curve is a well-known figure in chemistry. It is easy to plot this graph from experimental data by measuring pH as a function volume of added titrant; however, there is no simple mathematical equation of expressing pH as a function of titrant volume. The logistic function has been suggested but, as discussed in this paper, it is inadequate for modeling titration curves. Developed in this paper is a piecewise continuous function (with chemically meaningful parameters) of pH versus volume. A program has been written to display this function on a graphing calculator. This program can be used by students (1) to analyze the characteristics of pH titration curves, for example, the derivative and the presence of two inflection points, and (2) to interactively fit experimental titration data that they have collected.
    Type of Medium: Electronic Resource
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