Fourier transform photoelectron diffraction and its application to molecular orbitals and surface structure (open access)

Fourier transform photoelectron diffraction and its application to molecular orbitals and surface structure

Photoemission intensities from the molecular orbitals of c(2x2)CO/Pt(111) over a wide photon energy range were measured and analyzed by the same methods developed for structural studies using core levels. The 4{sigma} orbital center of gravity is found to be concentrated between the C and O atoms, while that of the 5{sigma} orbital lies between the C atom and the Pt surface. The C 1s photoelectron diffraction was used to determine the adsorption geometry. The earlier ambiguity that multiple scattering is needed to correctly model a {chi} curve while single scattering is sufficient for understanding major peaks in the ARPEFS-FTS is clarified by studying the clean Ni(111) surface. In the normal emission case, several different combinations of scattering events have similar path length differences (PLDs), and can either cancel each other or enhance the corresponding FT peak. In the off-normal case the degeneracy is greatly reduced due to the lower degree of symmetry. In normal emission AR PEFS, up to third order multiple scattering is needed to describe fully both the {chi} curve and its FT spectrum. To improve the spectral resolution in the ARPEFS-FT analysis, several new spectral analysis methods are introduced. With both autocorrelation autoregression (ACAR) and autocorrelation eigenvector …
Date: November 30, 1998
Creator: Zhou, Xin
System: The UNT Digital Library
Compact Intracloud Discharges (open access)

Compact Intracloud Discharges

None
Date: November 1, 1998
Creator: Smith, David A.
System: The UNT Digital Library
I. Advances in NMR Signal Processing. II. Spin Dynamics in Quantum Dissipative Systems (open access)

I. Advances in NMR Signal Processing. II. Spin Dynamics in Quantum Dissipative Systems

None
Date: November 1, 1998
Creator: Lin, Yung-Ya
System: The UNT Digital Library
Laser-plasma interactions relevant to Inertial Confinement Fusion (open access)

Laser-plasma interactions relevant to Inertial Confinement Fusion

Research into laser-driven inertial confinement fusion is now entering a critical juncture with the construction of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). Many of the remaining unanswered questions concerning NIF involve interactions between lasers and plasmas. With the eventual goal of fusion power in mind, laser-plasma interactions relevant to laser fusion schemes is an important topic in need of further research. This work experimentally addresses some potential shortcuts and pitfalls on the road to laser-driven fusion power. Current plans on NIF have 192 laser beams directed into a small cylindrical cavity which will contain the fusion fuel; to accomplish this the beams must cross in the entrance holes, and this intersection will be in the presence of outward-flowing plasma. To investigate the physics involved, interactions of crossing laser beams in flowing plasmas are investigated with experiments on the Nova laser facility at LLNL. It was found that in a flowing plasma, energy is transferred between two crossing laser beams, and this may have deleterious consequences for energy balance and ignition in NIF. Possible solutions to this problem are presented. A recently-proposed alternative to standard laser-driven fusion, the ''fast ignitor'' concept, is also experimentally addressed in …
Date: November 2, 1998
Creator: Wharton, Kenneth Bradford
System: The UNT Digital Library