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Full-Text Articles in Physics

Collisional Excitation Of Co By 2.3 Ev H Atoms, George C. Mcbane, Scott H. Kable, Paul L. Houston, George C. Schatz Oct 1990

Collisional Excitation Of Co By 2.3 Ev H Atoms, George C. Mcbane, Scott H. Kable, Paul L. Houston, George C. Schatz

Peer Reviewed Articles

Vibrational and rotational distributions of CO excited by collisions with 2.3 eV H atoms have been obtained by monitoring the products with vacuum ultraviolet (VUV) laser induced fluorescence. Translational-to-vibrational (T→V) transfer is dominated by the dynamics of collisions occurring in the two wells on the H+CO potential energy surface, one characterizing the HCO radical and the other characterizing COH. The measured vibrational distributions agree well with the results of trajectory calculations performed on the ab initio potential energy surface of Bowman, Bittman, and Harding (BBH). The measured rotational distributions show two significant differences from the calculated ones ...


Argon-Photoion–Auger-Electron Coincidence Measurements Following K-Shell Excitation By Synchrotron Radiation, Jon C. Levin, C. Biedermann, N. Keller, L. Liljeby, C.-S. O, R. T. Short, Ivan A. Sellin, Dennis W. Lindle Aug 1990

Argon-Photoion–Auger-Electron Coincidence Measurements Following K-Shell Excitation By Synchrotron Radiation, Jon C. Levin, C. Biedermann, N. Keller, L. Liljeby, C.-S. O, R. T. Short, Ivan A. Sellin, Dennis W. Lindle

Chemistry and Biochemistry Faculty Publications

Argon photoion spectra have been obtained for the first time in coincidence with K-LL and K-LM Auger electrons, as a function of photon energy. The simplified charge distributions which result exhibit a much more pronounced photon-energy dependence than do the more complicated noncoincident spectra. In the near-K-threshold region, Rydberg shakeoff of np levels, populated by resonant excitation of K electrons, occurs with significant probability, as do double-Auger processes and recapture of the K photoelectron through postcollision interaction.


Low-Temperature Epitaxial Growth Of Thin Metal Films, James W. Evans, D. E. Sanders, Patricia A. Thiel, Andrew E. Depristo Mar 1990

Low-Temperature Epitaxial Growth Of Thin Metal Films, James W. Evans, D. E. Sanders, Patricia A. Thiel, Andrew E. Depristo

Chemistry Publications

We present a different mechanism to explain the occurrence of long-lived oscillations in diffraction spot intensities during epitaxial growth of metal films on fcc (100) substrates at low temperature. Rather than rely on the common picture of cyclical nucleation and growth to produce the oscillations, the model invokes ‘‘downward funneling’’ deposition dynamics to fourfold-hollow adsorption sites.


Size‐Inconsistency Effects In Molecular Properties For States With Valence‐Rydberg Mixing: The Low‐Lying Π→Π∗ States Of Ethylene And Butadiene, Robert J. Cave Feb 1990

Size‐Inconsistency Effects In Molecular Properties For States With Valence‐Rydberg Mixing: The Low‐Lying Π→Π∗ States Of Ethylene And Butadiene, Robert J. Cave

All HMC Faculty Publications and Research

Ab initio results for the low‐lying 1B1u states of ethylene are used to discuss size‐inconsistency effects on calculated molecular properties for states where valence‐Rydberg mixing is important. Results for the expectation value of x2, x being the coordinate perpendicular to the plane of the molecule, are presented from quasidegenerate variational perturbation theory and multireference configuration‐interaction calculations. These results are compared with values from previous studies. It is argued that size inconsistency in configuration‐interaction studies can have a significant effect on estimated molecular properties. Calculations on several low‐lying states of butadiene are also reported where ...


Cluster Diffusivity: Structure, Correlation, And Scaling, H. C. Kang, P. A. Thiel, James W. Evans Jan 1990

Cluster Diffusivity: Structure, Correlation, And Scaling, H. C. Kang, P. A. Thiel, James W. Evans

Physics and Astronomy Publications

We have investigated the diffusion of clusters on a triangular lattice using Monte Carlo simulations. A cluster is defined as a two‐dimensional collection of particles which are connected to each other, either directly or indirectly through other particles in the cluster, by nearest‐neighbor bonds. Each particle is allowed to hop, with probability αδb/2/(α−δb/2+αδb/2), to a vacant nearest‐neighbor site with the constraint that the hop does not break the cluster. The change in the number of bonds is given by δb. The equilibrium clusters are correlated animals with ...


Inequivalent Models Of Irreversible Dimer Filling: ‘‘Transition State’’ Dependence, R. S. Nord, James W. Evans Jan 1990

Inequivalent Models Of Irreversible Dimer Filling: ‘‘Transition State’’ Dependence, R. S. Nord, James W. Evans

Physics and Astronomy Publications

Irreversible adsorption of diatomics on crystalline surfaces is sometimes modeled as random dimer filling of adjacent pairs of sites on a lattice. We note that this process can be implemented in two distinct ways: (i) randomly pick adjacent pairs of sites,  jj’, and fill  jj’ only if both are empty (horizontal transition state); or (ii) randomly pick a single site,  j, and if  j and at least one neighbor are empty, then fill  j and a randomly chosen empty neighbor (vertical transition state). Here it is instructive to consider processes which also include competitive random monomer filling of ...