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Full-Text Articles in Physics

Valence-Band Photoemission In La And Pr: Connections With The Ce Problem, David Michael Wieliczka, C. G. Olson, David W. Lynch Jun 1984

Valence-Band Photoemission In La And Pr: Connections With The Ce Problem, David Michael Wieliczka, C. G. Olson, David W. Lynch

Physics and Astronomy Publications

Energy distribution curves from La and Pr were taken from 32 to 80 eV photon energies. Above 50 eV the valence-band photoemission in La is very weak, implying that previous studies of Ce have underemphasized the 4f contributions. Pr exhibits two peaks attributable to 4f electrons, similar to the structures in Ce.


High-Resolution Photoemission Study Of Γ- And Α-Cerium, David Michael Wieliczka, C. G. Olson, David W. Lynch Mar 1984

High-Resolution Photoemission Study Of Γ- And Α-Cerium, David Michael Wieliczka, C. G. Olson, David W. Lynch

Physics and Astronomy Publications

High-resolution photoemission studies on the α and γ phases of cerium show changes in the binding energies of the two4f-related features. The location of the two 4f-related features in the γ phase are at -0.2 and -2.0 eV, while in the αphase these features are located at the Fermi level and -2.1 eV. These results are a direct test of the theories proposed to explain the presence of the two features.


Irreversible Random And Cooperative Processes On Lattices: Spatial Correlations, James W. Evans, D. R. Burgess, D. K. Hoffman Jan 1984

Irreversible Random And Cooperative Processes On Lattices: Spatial Correlations, James W. Evans, D. R. Burgess, D. K. Hoffman

Physics and Astronomy Publications

For processes where ‘‘filling’’ events occur irreversibly and, in general, cooperatively at the sites of a lattice, the minimal closed hierarchy of rate equations involves only probabilities for (effectively) connected subconfigurations of empty sites. Extended hierarchies of equations for (effectively) disconnected empty subconfigurations couple back to these. Here we consider a solution to the latter via previously developed exact and approximate truncation schemes based on a shielding property of empty sites. Numerical results for several processes are presented for correlation behavior in both autocatalytic and autoinhibitory rate regimes. The asymptotic large separation behavior of the spatial correlations is analyzed most ...


Dynamics Of Two-Point Spatial Correlations For Randomly Hopping Lattice Gases: One-Dimensional Models, James W. Evans, D. K. Hoffman Jan 1984

Dynamics Of Two-Point Spatial Correlations For Randomly Hopping Lattice Gases: One-Dimensional Models, James W. Evans, D. K. Hoffman

Physics and Astronomy Publications

We consider the randomization of correlated, translationally invariant distributions of indistinguishable particles on lattices by random hopping, possibly involving several jump distances with generally different rates (and where double occupancy is excluded). Probabilities for various subconfigurations of n empty sites satisfy infinite closed sets of linear equations (for each n) in which the generator of the dynamics is self-adjoint. We provide a detailed spectral analysis of this generator for the two-point probabilities (or corresponding correlations) on a one-dimensional lattice. For just nearest-neighbor (1NN) and second-nearest-neighbor (2NN) jumps, the dynamics changes smoothly as a function of the ratio of the 2NN- ...


Exactly Solvable Irreversible Processes On Bethe Lattices, James W. Evans Jan 1984

Exactly Solvable Irreversible Processes On Bethe Lattices, James W. Evans

Physics and Astronomy Publications

We consider the kinetics of processes where the sites of a Bethe lattice are filled irreversibly and, in general, cooperatively by monomers, dimers, or polyatomics. For nearest neighbor and sometimes more general cooperative effects (including random filling as a special case), we show that the infinite hierarchy of rate equations for probabilities of empty subconfigurations can be exacty truncated and solved using a shielding property of empty sites. We indicate, in certain cases, a connection between these Bethe lattice solutions and certain approximate truncation solutions for corresponding processes on ‘‘physical’’ 2‐D and 3‐D lattices with the same coordination ...


The Kinematic Apse And Jz‐Preserving Propensities For Nonreactive, Dissociative, And Reactive Polyatomic Collisions, D. K. Hoffman, James W. Evans, D. J. Kouri Jan 1984

The Kinematic Apse And Jz‐Preserving Propensities For Nonreactive, Dissociative, And Reactive Polyatomic Collisions, D. K. Hoffman, James W. Evans, D. J. Kouri

Physics and Astronomy Publications

We consider the generalization of the kinematic apse to nonreactive polyatom–polyatom impulsive collisions, dissociative atom–molecule impulsive collisions,and (partially) impulsive reactive atom–diatom collisions. Appropriate generalizations of the kinematic apse are obtained along which there is a classical propensity for preserving the projection of the total intrinsic spin. In the case of reactive scattering, we discuss several different situations for which such a propensity occurs. For reactive systems in which no such propensity exists, the analysis may still provide a basis for classifying reactions.


Exactly Solvable Irreversible Processes On One‐Dimensional Lattices, N. O. Wolf, James W. Evans, D. K. Hoffman Jan 1984

Exactly Solvable Irreversible Processes On One‐Dimensional Lattices, N. O. Wolf, James W. Evans, D. K. Hoffman

Physics and Astronomy Publications

We consider the kinetics of a process where the sites of an infinite 1‐D lattice are filled irreversibly and, in general, cooperatively by N‐mers (taking Nconsecutive sites at a time). We extend the previously available exact solutionfor nearest neighbor cooperative effects to range N cooperative effects. Connection with the continuous ‘‘cooperative car parking problem’’ is indicated. Both uniform and periodic lattices, and empty and certain partially filled lattice initial conditions are considered. We also treat monomer ‘‘filling in stages’’ for certain highly autoinhibitory cooperative effects of arbitrary range.


Competing Irreversible Cooperative Reactions On Polymer Chains, James W. Evans, D. K. Hoffman, D. R. Burgess Jan 1984

Competing Irreversible Cooperative Reactions On Polymer Chains, James W. Evans, D. K. Hoffman, D. R. Burgess

Physics and Astronomy Publications

We analyze model processes involving competition between several irreversible reactions at the sites of a 1D, infinite, uniform polymer chain. These reactionscan be cooperative, i.e., the corresponding rates depend on the state of the surrounding sites. An infinite hierarchy of rate equations is readily derived for the probabilities of various subconfigurations. By exploiting a shielding property of suitable blocks of unreacted sites, we show how exact hierarchy truncation and solution is sometimes possible. The behavior of solutions is illustrated in several cases by plotting families of ‘‘reaction trajectories’’ for varying ratios of reactant concentrations ...