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  • 1
    Electronic Resource
    Electronic Resource
    Velocity-aligned photofragment dynamics: Stereodynamics in the reaction oxygen atom(1D) + nitrous oxide .fwdarw. nitric oxide + nitric oxide (1991)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 8169-8174 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100174a028
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamics of the N(4Su) + NO(X 2Π) → N2(X 1Σg+) + O(3Pg) atmospheric reaction on the 3A‘ ground potential energy surface. I. Analytical potential energy surface and preliminary quasiclassical trajectory calculations (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 5542-5553 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The N(4Su)+NO(X 2Π)→N2(X 1Σg+)+O(3Pg) reaction plays an important role in the upper atmosphere chemistry and as a calibration system for discharge flow systems. Surprisingly, very little theoretical and experimental work has been devoted to the characterization of the dynamical features of this system. In this work a Sorbie–Murrell expression for the lowest 3A‘ potential energy surface (PES) connecting reactants in their ground electronic states based upon the fitting of an accurate ab initio CI grid of points has been derived. The PES fitted shows no barrier to reaction with respect to the reactants asymptote in accordance with experimental findings and becomes highly repulsive as the NNO angle is varied away from the saddle point geometry. The results of preliminary quasiclassical trajectory calculations on this surface reproduce very well the experimental energy disposal in products, even though the vibrational distribution derived from trajectories seems to be a bit cooler than the experimental data. Moreover, thermal rate constants derived from trajectories are in excellent accordance with experimental values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463787
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  • 3
    Electronic Resource
    Electronic Resource
    A comparison between experimental and theoretical excitation functions for the O++H2 (4A‘) system using trajectory calculations over a wide energy range (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 2927-2935 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The O++H2 prototypic ion–molecule reaction was recently studied in our group using the quasiclassical trajectory method on a ground model potential-energy surface of the system inferred from both experimental and theoretical information and reasonable assumptions, fitted using a London–Eyring–Polanyi–Sato surface modified to include an ion–induced-dipole interaction term. The theoretical results previously reported agreed rather well with the available experimental information. In view of the latest experimental findings, we present in this contribution the results of new trajectory calculations on the above-mentioned surface, covering a wide range of relative translational energies of reactants. The accord between the experimental determinations and the present theoretical evaluations is excellent at relative energies below 1.0 eV, while for higher energies the potential-energy surface, even though still yielding reasonably good results, provides a worse agreement. The observed discrepancies should be attributed either to the too attractive character of the surface or to the interfering influence of the competing O++H2→O+H2+ charge-transfer process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464120
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamics of the N(4Su)+NO(X 2Π)→N2(X 1Σ+g)+O(3Pg) atmospheric reaction on the 3A‘ ground potential energy surface. II. The effect of reagent translational, vibrational, and rotational energies (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 1719-1733 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effect of translational vibrational, and rotational energies on the dynamics of the N(4Su)+NO(X 2Π)→N2(X 1Σg+)+O(3Pg) reaction has been examined using a Sorbie–Murrell analytical fitting of a grid of ab initio configuration interaction (CI) points for the 3A‘ ground potential energy surface reported by the authors in a previous work. Translational energy is shown to increase total reaction cross section for all the initial rovibrational states of reactants considered. The reaction mode analysis points towards a direct mechanism and a strong influence of the shape of the potential energy surface on the reactivity, especially at low relative collision energies. Vibrational excitation of the NO reactant molecule changes the total reaction cross section values moderately, while increasing the initial rotational states of NO at low fixed relative collision energies decreases the reaction cross section sharply, eventually becoming zero for the highest J values explored. By comparing with model calculations on the same surface involving extreme H+HL and L+LH mass combinations, the microscopic reaction mechanism is shown to imply product molecules being created with rotational angular momentum (J') oriented preferentially antiparallel with respect to their orbital angular momentum (l') at low relative energies, with loss of orientation for higher relative energies. Thus, the surface used indicates a strong vector correlation between l' and J' and also an important influence in equipartitioning total angular momentum between the rotational and orbital angular momenta of products. Comparison with unfortunately scarce experimental data (e.g., fraction of vibrational energy in products and rate constants) shows a very good agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465289
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamics of the N(4S)+NO(X 2Π)→N2(X 1Σ+g)+O(3P) atmospheric reaction on the 3A″ ground potential energy surface. III. Quantum dynamical study and comparison with quasiclassical and experimental results (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 4496-4508 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A detailed reactive–infinite-order sudden approximation (R-IOSA) study of the reactivity of the N+NO→N2+O system has been carried out in the 0.0038 to 1.388 eV translational energy range and the results have been compared with the existing quasiclassical trajectory (QCT) and experimental data available. The general features already observed in the previous QCT studies are reproduced qualitatively in the quantum study, even though some differences arise in the product vibrational distributions and state-to-state opacity functions in the low energy range. The observed differences have been justified in terms of the anisotropy of the potential energy surface and the vibrational barriers to reaction at fixed angles. A strong vibrational adiabaticity is observed quantally in the low translational energy range, disappearing at moderately high collision energies (around 0.3 eV), where a simple Franck–Condon type model is capable of describing the evolution of the vibrational distribution with translational energy. The vibrational distributions at fixed angles have been discussed within the context of Polanyi's and Light's correlation between products vibrational excitation and the features of the potential energy surface. The validity of extending the conclusions drawn from collinear to three-dimensional (3D) collisions is discussed. Finally, the detailed reaction mechanism is examined in light of the vibrational matrix elements of the close-coupling interaction matrix. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470638
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  • 6
    Electronic Resource
    Electronic Resource
    A theoretical approach to the O(1D)+H2O(X 1A1) reaction: Ab initio potential energy surface and quasiclassical trajectory dynamics study (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 6736-6747 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An ab initio study of the ground potential energy surface (PES) of the O(1D)+H2O system has been performed, employing Møller–Plesset methods. From the stationary and additional points calculated, the ground PES has been modeled as a triatomic system, with an OH group of the H2O molecule treated as a single atom of 17.0 amu. The rate constant of reaction (1), O(1D)+H2O→2OH (main reaction channel), estimated from the quasiclassical trajectory (QCT) calculations is reasonably close to the recommended experimental value. For the relative translational energies explored (ET=0.234, 0.303, and 0.443 eV) and H2O at T=300 K, the QCT OH vibrational populations are in good agreement with the experimental values reported for the new OH fragment, but the QCT OH average rotational energies are in general quite larger than the experimental ones. Regarding the stereodynamics, for ET=0.234 eV there is not a clear tendency to a particular rotational alignment of the OH product with respect to the initial relative velocity vector, in agreement with experiments. The QCT results also show that nearly all reactive trajectories leading to reaction (1) take place through an insertion microscopic mechanism, which, even at the highest ET value considered (0.443 eV), is mainly (70%) a nondirect one. The collision complex has an average lifetime of about three rotational periods and a geometry around that of the HO(OH) hydrogen peroxide molecule. The QCT results concerning the microscopic mechanism of reaction (1) are in agreement with the suggested ones by the experimentalists to interpret their results. The present study should be considered as a starting point in the study of reaction (1) from which different aspects on the dynamics may be learned. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1311295
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  • 7
    Electronic Resource
    Electronic Resource
    An ab initio analytical potential energy surface for the O(3P)+CS(X 1Σ+)→CO(X 1Σ+)+S(3P) reaction useful for kinetic and dynamical studies (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 10999-11006 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A total of 816 ab initio points at the PUMP4/6-311G(2d) level were used to derive an analytical expression for the lowest 3A′ adiabatic potential energy surface (PES) of the reaction O(3P)+CS(X 1Σ+)→CO(X 1Σ+)+S(3P). Thermal rate constants calculated using the variational transition state theory and semiclassical tunneling correction were used as a tool to determine the optimum analytical surface. This was done by comparing the calculated rate constant at room and lower temperatures with the experimental values. The best analytical surface (PES 3) reproduces the rate constant at low temperatures well. However, it has not been possible to obtain an analytical PES capable of reproducing both the rate constant at 300 K and the activation energy (150–300 K range). At higher temperatures, the contribution of the lowest 3A″ adiabatic potential energy surface to the rate constant seems to be important to reproduce the experimental data. At present, the PES 3 is the most suitable analytical surface to be used for kinetic and dynamical single surface studies. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472899
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  • 8
    Electronic Resource
    Electronic Resource
    Ab initio and quasiclassical trajectory study of the N(2D)+NO(X 2Π)→O(1D)+N2(X 1Σg+) reaction on the lowest 1A′ potential energy surface (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 10983-10998 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this work we have carried out ab initio electronic structure calculations, CASSCF/CASPT2 with the Pople's 6-311G(2d) basis set on the ground singlet potential energy surface (1 1A′ PES) involved in the title reaction. Transition states, minima and one 1 1A′/2 1A′ surface crossing have been characterized, obtaining three NNO isomers with the energy ordering: NNO (1Σ+)〈cyclic−C2v NON(1A1)〈NON(1Σg+). Approximately 1250 ab initio points have been used to derive an analytical PES which fits most of the stationary points, with a global root-mean-square deviation of 1.12 kcal/mol. A quasiclassical trajectory study at several temperatures (300–1500 K) was performed to determine thermal rate constants, vibrational and rovibrational distributions and angular distributions. The dynamics of this barrierless reaction presents a predominant reaction pathway (96% at 300 K) with very short-lived collision complexes around the NNO minimum, which originate backward scattering and a similar fraction of vibrational and translational energy distributed into products. At higher temperatures other reaction pathways involving NON structures become increasingly important as well as the N-exchange reaction (3.02% of the branching ratio at 1500 K), this latter in accord with experimental data. It is concluded that the physical electronic quenching of N(2D) by NO should be negligible against all possible N(2D)+NO reaction channels. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1327263
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  • 9
    Electronic Resource
    Electronic Resource
    Theoretical investigation of the eight low-lying electronic states of the cis- and trans-nitric oxide dimers and its isomerization using multiconfigurational second-order perturbation theory (CASPT2) (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 6608-6624 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this work we have carried out ab initio electronic structure calculations, CASSCF/CASPT2 and CASSCF/MRCI-SD+Q with several Pople's and correlation-consistent Dunning's basis sets, of the planar cis- and trans-NO dimers for the lowest eight electronic (singlet and triplet) states. The geometry, frequencies, dipole moment, binding energy, and vertical excitation energies are predicted with an accuracy close to or even better than the best reported ab initio previous results for some of these properties, and in very good agreement with the available experimental data. CASPT2 optimized geometries show the existence of at least four shallow NO-dimers (i.e., two cis-(NO)2 (1A1 and 3B2) and two trans-(NO)2 (1Ag and 3Au)), although CASSCF optimization with CASPT2 pointwise calculations indicate the existence of other less stable dimers, on the excited states. Vertical excitation energies were calculated for these four dimers. For the cis-NO dimer, the ordering and the energy spacings between the excited states (i.e., 1A1, 3B2, 1B2, 2nd 1A1, 1A2, 3A2, 3B1, 2nd 3B1) are very similar to those found in a recent MRCI-SD study. The singlet cis-NO dimer (1A1) is the most stable one in almost quantitative accord with the experimental data, and in disagreement with previous density functional theory studies. A nonplanar transition state for the singlet trans ↔ cis isomerization has also been fully characterized. This leads to an almost negligible energy barrier which would originate a rapid isomerization to the most stable cis-NO dimer at low temperatures, in accord with the experimental difficulties to measure the properties of the trans-NO dimer. Not only are basis set superposition error corrections necessary to evaluate accurately the binding energies, but also to determine the NN distance of these symmetrical dimers. Some problems regarding the symmetry of the wave function were found for the symmetrical NO dimers and for the NO+NO asymptote, and several approximate solutions were proposed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481234
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  • 10
    Electronic Resource
    Electronic Resource
    An analytical representation of the ground potential energy surface (2A′) of the H+Cl2→HCl+Cl and Cl+HCl→HCl+Cl reactions, based on ab initio calculations (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 3168-3177 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this work we have studied at an ab initio level the lowest 2A′ potential energy surface (PES) of the HCl2 system. This PES is involved in the H(2S)+Cl2(X 1Σg+)→HCl(X 1Σ+)+Cl(2P) and Cl(2P)+HCl(X 1Σ+)→HCl(X 1Σ+)+Cl(2P) gas phase elementary chemical reactions. The former reaction is an important chemical laser while the second one is the most frequently used prototype of heavy–light–heavy reaction. A large number of points on the 2A′ PES have been calculated at the PUMP2/6-311G(3d2 f,3p2d) ab initio level. The ab initio calculations show the existence of two angular transition states with negligible or very small barriers to collinearity. This and other properties of the PES are in agreement with previous studies. An analytical expression based on a many-body expansion has been used to obtain a satisfactory fit of the 740 ab initio points calculated, with a root-mean-square deviation within the range of the estimated ab initio method error margin. This analytical representation of the 2A′ PES has been used to evaluate the variational transition state theory thermal rate constants of the above-mentioned reactions, including also the Cl+DCl reaction, and quite good agreement has been obtained when comparing with experimental results. The analytical PES obtained in this work is suitable for use in studies on the kinetics and dynamics of the HCl2 system. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475713
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