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  • 1
    Digitale Medien
    Digitale Medien
    Anisotropy of molecular interactions: a quantitative study for the neon-nitrogen case (1989)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 7629-7635 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100359a020
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  • 2
    Digitale Medien
    Digitale Medien
    Second virial coefficients for O2 and N2 mixtures with rare gases: A computational assessment (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5352-5358 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Second virial coefficients as function of temperature are computed for the title molecular systems interacting with He, Ne, and Ar. The relevant anisotropic forces are obtained via accurate potential functions tested earlier through the analysis of several, different properties of the various systems. The relevant quantum corrections are also computed, in addition to the classical results, and their effects analyzed vis à vis the available experimental data. The influence of such corrections on the very low-T behavior of the virial coefficients and on the determination of the Boyle temperatures is also shown and discussed. All examined potential functions are found to yield B(T) values in rather good accord with experiments, in spite of their marked differences in anisotropic behavior and in the shape of their potential well regions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457583
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  • 3
    Digitale Medien
    Digitale Medien
    Transport and relaxation cross sections for He–N2 mixtures: A test of a multiproperty interaction (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 6720-6729 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Full quantum calculations of several transport and relaxation cross sections have been carried out for the title system, using the multiproperty potential energy surface obtained earlier by Gianturco et al. [Chem. Phys. 109, 417 (1986)] which has been recently shown to be one of the most reliable descriptions of the He–N2 interaction. A rigorous close coupling (CC) treatment of the scattering problem turns out to be the only realistic choice for evaluating viscomagnetic relaxation data and for anisotropy-dependent nonequilibrium properties. A comparison of the present calculations with classical trajectory (CT) estimates is carried out for several transport cross sections as function of both the collision energy and the temperature of the mixture. It is clearly shown by the present results that classical treatments markedly differ from the quantum calculations at collision energies which are comparable with the average well depth of the chosen interaction. On the other hand, CT and CC values are nearly coincident at higher collision energies for all the computed properties. Thus, their combined use in evaluating the temperature dependence of diffusion and viscosity coefficients reveals the high quality of the present multiproperty interaction vis à vis the experimental findings examined in this work.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.463678
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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
    The He–Co2 interaction revisited: Approximate rotational energy transfer efficiency indices and computed transport coefficients (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1641-1651 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Of the several anisotropic interactions suggested over the years for the title system, two of the most recent ones have been tested against experimental total differential cross sections, energy loss angular distributions, and transport coefficients. In the present work, they are examined again in order to compare them in a calculation over a broader range of transport properties, using the approximate infinite order sudden approximation (IOSA) scheme for the dynamics and getting first- and second-order contributions to the Chapman–Cowling expansion in the kinetic theory of dilute gaseous mixtures. The various observables are found to be very close to the experiments for both potential functions, thereby making it still difficult to establish clearcut differences between them from the study of the above properties alone. The novelty of the present study, however, is to show that various recently proposed efficiency indices for the rotational energy transfer (RET) collisions are able to exhibit marked differences between the two surfaces and to unequivocally select one of them as the more anisotropic of the two. Because of the low value of such indices, one is also able to explain why the IOSA approximation should work well for computing the transport coefficients of this system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.459092
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  • 6
    Digitale Medien
    Digitale Medien
    A test of recently proposed He–N2 interactions: Angular distributions and rotationally inelastic collisions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2639-2650 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Three recently proposed anisotropic potential energy surfaces (PES) for the He+N2 (1Σg) system are employed to compute differential scattering cross sections, total and state-to-state rotationally inelastic, at two collision energies for which accurate molecular beam experiments are already available. The experiments have provided scattering angular distributions which resolved, in one case, rotational energy losses (at 27.7 meV) and which, in the other case, were able to yield only total differential cross sections (at 70.4 meV). Rigorous close-coupling (CC) calculations at both energies are compared with IOSA (infinite order sudden approximation) results and with the experimental data. The ensuing discussion shows that only one PES, the recently proposed M3SV form, appears to have the correct anisotropic behavior in agreement with all experimental data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.455961
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  • 7
    Digitale Medien
    Digitale Medien
    Second-order corrections to transport coefficients of binary gaseous mixtures: N2 with He, Ne, and Ar (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2525-2536 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The usual kinetic theory of dilute gaseous mixtures is employed, via the infinite-order sudden (IOS) decoupling scheme for the dynamics, to obtain generalized collision integrals and transport properties for molecular mixtures containing N2 and various rare gases (He, Ne, and Ar). The relevant interaction potentials originate from a previous study [F. A. Gianturco, M. Venanzi, and A. S. Dickinson, Mol. Phys. 65, 563 (1988)] of the above systems in which a multiproperty analysis of their quality and reliability was attempted by combining scattering data, when available, with diffusion coefficients and interaction viscosity data to select the most accurate of the potential energy surfaces (PES) at hand. The extension of the calculations to second-order effects allows us to test the importance of such corrections on diffusion and viscosity coefficients, to follow their dependence on the mole fraction of the mixtures, to obtain thermal diffusion and thermal conductivity results and to futher assess the feasibility of multiproperty tests of simple atom–diatom interactions via the calculation of a broader range of transport coefficients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457012
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  • 8
    Digitale Medien
    Digitale Medien
    Excited electronic states of protonated acetylene (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 7965-7968 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The classical structure of protonated C2H2, and the nonclassical, bridge arrangement for the same species, have been studied along the rearrangement pathway with the intention of throwing new light on the role played by the electronically excited state of the full system in the collisions between a proton and the C2H2 molecule. Furthermore, the potential energy on one possible dissociation path into acetylene and proton has been obtained. Extensive, multiple reference double-excitation configuration-interaction (MRD-CI) calculations have been carried out for the first time with the specific aim of locating energies and geometries of the ground and of the lower-lying excited states of the C2H+3 species as it goes from one structure to the other and from the C2V geometry to separated C2H2+H+ or C2H+2+H fragments. The results show an interesting behavior of the excited states and provide a preliminary understanding of the full potential energy surfaces thought to be involved in charge-transfer (CT) inelastic collisions at low and intermediate energies (E≤100 eV).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.461327
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  • 9
    Digitale Medien
    Digitale Medien
    Classical trajectory calculations of transport and relaxation properties for Ar–N2 mixtures (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5552-5562 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Classical trajectory calculations of transport and relaxation properties have been performed for Ar–N2 mixtures using the potential energy surface (PES) recently determined by Bowers et al. [J. Chem. Phys. 88, 5465 (1988)]. Generalized cross sections have been computed in the temperature range 77.3–1000 K. Extensive comparisons have been carried out with available measurements and with other calculations. The present system exhibits greater efficiency for rotational energy transfer (RET) processes and its interaction shows a deeper potential well than that of previously computed surfaces. A larger number of trajectories (up to 28 500 at the lowest total energy examined) has therefore been required to obtain converged results. The PES employed here shows impressive agreement with the available measurements for a wide variety of properties of the system and appears to be the most reliable currently available for Ar–N2 gaseous mixtures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.459625
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  • 10
    Digitale Medien
    Digitale Medien
    Quantum and classical calculations of transport and relaxation cross sections in He–CO mixtures (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 3833-3844 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Rigorous quantum and classical calculations for transport and relaxation properties of the gaseous mixture of He with CO have been carried out over a broad range of temperatures. The interaction potential employed was the one recently suggested from molecular beam experiments (W. Dilling, Ph.D. thesis, University of Göttingen, Germany, 1985) and the calculations were carried out with the correct dynamical couplings between tensorial basis sets in the quantum case, leading to the usual close-coupled (CC) equations. Classical trajectory (CT) calculations were also carried out and compared with the CC results. A combined use of CC and CT results, together with an appropriate choice of partition functions, is found to produce rather good agreement with the experimental findings for diffusion and mixture viscosity coefficients. The present results suggest ways for further testing the original potential energy surface and for extending the multiproperty analysis of it started earlier on with the scattering data of Dilling and the pressure broadening data of Green, Boissoles, and Boulet [J. Quant. Spectrosc. Radiat. Transfer 39, 33 (1988)].
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.464012
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