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Full-Text Articles in Physics

A Theoretical Investigation Of The Geometries, Vibrational Frequencies, And Binding Energies Of Several Mixed Alkali Halide Dimers, Robert J. Cave, Ian Ono '94 Dec 1993

A Theoretical Investigation Of The Geometries, Vibrational Frequencies, And Binding Energies Of Several Mixed Alkali Halide Dimers, Robert J. Cave, Ian Ono '94

All HMC Faculty Publications and Research

Results are presented from ab initio calculations on several mixed alkali halide dimers made up of Li, Na, F, and Cl. All of the dimers are investigated at the restricted Hartree–Fock level to provide ab initio estimates of geometries, vibrational frequencies, and binding energies. The dimer LiNaF2 is then treated using a variety of basis sets at the Hartree–Fock level, as well as at correlated levels (second‐order Møller–Plesset and coupled‐cluster singles and doubles) to examine the sensitivity of the calculations to use of higher levels of theory. The results are then compared to the experimental ...


Response To "Comment On 'The Weakest Bond: Experimental Observation Of Helium Dimer'", Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, Ronald Gentry Nov 1993

Response To "Comment On 'The Weakest Bond: Experimental Observation Of Helium Dimer'", Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, Ronald Gentry

Peer Reviewed Articles

No abstract provided.


Influence Of Retardation On The Vibrational Wave Function And Binding Energy Of The Helium Dimer, Fei Luo, Geunsik Kim, George C. Mcbane, Clayton F. Giese, W. Ronald Gentry Mar 1993

Influence Of Retardation On The Vibrational Wave Function And Binding Energy Of The Helium Dimer, Fei Luo, Geunsik Kim, George C. Mcbane, Clayton F. Giese, W. Ronald Gentry

Peer Reviewed Articles

Because of the extremely small binding energy of the helium dimer, the nuclear wave function is delocalized over an extremely large range of separations. One might therefore expect the properties of this extraordinary species to be sensitive to the potential at very large internuclear distances, r, where relativistic corrections to the usual van der Waals interaction may be important. We have estimated the effect of retardation, which changes the r-6 dependence of the potential to r-7 in the limit of large r, and have found that the binding energy and expectation value (r) are indeed significantly affected by ...


A Theoretical Investigation Of The Geometries, Vibrational Frequencies, And Binding Energies Of Several Alkali Halide Dimers, Robert P. Dickey '93, David Maurice '91, Robert J. Cave, Richard J. Mawhorter Feb 1993

A Theoretical Investigation Of The Geometries, Vibrational Frequencies, And Binding Energies Of Several Alkali Halide Dimers, Robert P. Dickey '93, David Maurice '91, Robert J. Cave, Richard J. Mawhorter

All HMC Faculty Publications and Research

Results are presented from ab initio calculations on the symmetrical alkali halide dimers made up of Li, Na, K, F, and Cl. We examine the sensitivity of representative monomer and dimer geometries to the variation of the basis set with and without polarization and diffuse functions. The geometries are then compared with available experimental results. We have also calculated vibrational frequencies at the restricted Hartree–Fock level and examined the changes in geometry brought about by correlation using second‐order Møller–Plesset perturbation theory. It is found that Hartree–Fock theory in a modest basis set with diffuse and polarization ...


Advances In Pultiple-Pulse Radio-Frequency-Gradient Imaging Of Solids, John Marohn, David N. Shykind, Margat H. Werner, Daniel P. Weitekamp Jan 1993

Advances In Pultiple-Pulse Radio-Frequency-Gradient Imaging Of Solids, John Marohn, David N. Shykind, Margat H. Werner, Daniel P. Weitekamp

Review of Progress in Quantitative Nondestructive Evaluation

Magnetic resonance imaging (MRI) has become the premier tool for the non-destructive evaluation of soft tissue in living systems [1]. Established liquid-state MRI strategies are generally found to be inappropriate for the imaging of rigid solids, because the linewidth for nuclear magnetic resonance in solids is orders-of-magnitude larger than in liquids. Methods currently under development for the NMR imaging of solids either involve the use of very large (fringe-field) magnetic field gradients to encode spatial information over very short periods of time [2], or employ multiple-pulse line-narrowing techniques that prolong a solid’s apparent transverse relaxation time [3–7]. In ...


High-Energy Behavior Of The Double Photoionization Of Helium From 2 To 12 Kev, Jon C. Levin, Ivan A. Sellin, B. M. Johnson, Dennis W. Lindle, R. D. Miller, Y. Azuma, H. G. Berry, D.-H. Lee, N. Berrah Jan 1993

High-Energy Behavior Of The Double Photoionization Of Helium From 2 To 12 Kev, Jon C. Levin, Ivan A. Sellin, B. M. Johnson, Dennis W. Lindle, R. D. Miller, Y. Azuma, H. G. Berry, D.-H. Lee, N. Berrah

Chemistry and Biochemistry Faculty Publications

We report the ratio of double-to-single photoionization of He at several photon energies from 2 to 12 keV. By time-of-Aight methods, we find a ratio consistent with an asymptote at 1.5%±0.2%, essentially reached by h v≈4 keV. Fair agreement is obtained with older shake calculations of Byron and Joachain [Phys. Rev. 164, 1 (1967)], of Aberg [Phys. Rev. A 2, 1726 (1970)], and with recent many-body perturbation theory (MBPT) of Ishihara, Hino, and McGuire [Phys. Rev. A 44, 6980 (1991)]. The result lies below earlier MPBT calculations by Amusia et al. [J. Phys. B 8, 1248 ...


Pairwise And Many-Body Contributions To Interaction Potentials In He(N) Clusters, Carol A. Parish, Clifford E. Dykstra Jan 1993

Pairwise And Many-Body Contributions To Interaction Potentials In He(N) Clusters, Carol A. Parish, Clifford E. Dykstra

Chemistry Faculty Publications

High level ab initio calculations have been carried out to assess the pairwise additivity of potentials in the attractive or well regions of the potential surfaces of clusters of helium atoms. A large basis set was employed and calculations were done at the Brueckner orbital coupled cluster level. Differences between calculated potentials for several interacting atoms and the corresponding summed pair potentials reveal the three‐body and certain higher order contributions to the interaction strengths. Attraction between rare gas atoms develops from dispersion, and so helium clusters provide the most workable systems for analyzing nonadditivity of dispersion. The results indicate ...


Zgb Surface Reaction Model With High Diffusion Rates, James W. Evans Jan 1993

Zgb Surface Reaction Model With High Diffusion Rates, James W. Evans

Physics and Astronomy Publications

The diffusionless ZGB (monomer–dimer) surface reaction model exhibits a discontinuous transition to a monomer‐poisoned state when the fraction of monomer adsorption attempts exceeds 0.525. It has been claimed that this transition shifts to 2/3 with introduction of rapid diffusion of the monomerspecies, or of both species. We show this is not the case, 2/3 representing the spinodal rather than the transition point. For equal diffusion rates of both species, we find that the transition only shifts to 0.5951±0.0002.


Kinetics Of The Monomer-Monomer Surface Reaction Model, James W. Evans, T. R. Ray Jan 1993

Kinetics Of The Monomer-Monomer Surface Reaction Model, James W. Evans, T. R. Ray

Physics and Astronomy Publications

The two-dimensional monomer-monomer (AB) surface reaction model without diffusion is considered for infinitesimal, finite, and infinite reaction rates k. For equal reactant adsorption rates, in all cases, simulations reveal the same form of slow poisoning, associated with clustering of reactants. This behavior is also the same as that found in simulations of the two-dimensional voter model studied in interacting-particle systems theory. The voter model can also be obtained from the dimer-dimer or monomer-dimer surface reaction models with infinitesimal reaction rate. We provide a detailed elucidation of the slow poisoning kinetics via an analytic treatment for the k=0+ AB reaction ...


The Car‐Parking Limit Of Random Sequential Adsorption: Expansions In One Dimension, M. C. Bartelt, James W. Evans, M. L. Glasser Jan 1993

The Car‐Parking Limit Of Random Sequential Adsorption: Expansions In One Dimension, M. C. Bartelt, James W. Evans, M. L. Glasser

Physics and Astronomy Publications

We consider the irreversible random sequential adsorption of particles taking ksites at a time, on a one‐dimensional lattice. We present an exact expansion for the coverage, θ(t,k)=A0(t)+A1(t)k−1+A2(t)k−2+..., for times, 0≤tO(k), and at saturation t=∞. The former is new and the latter extends Mackenzie’s results [J. Chem. Phys. 37, 723 (1962)]. For these expansions, we note that the coefficients Ai≥1(∞) are not obtained as large‐t limits of the Ai≥1(t). Finally, we comment on the ...