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'Electron momentum density' in keywords Facet   Publication Year 1993  [X]
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1993[X]
1Author    F. Bell, Th Tschentscher, J. R. Schneider, A. J. RollasonRequires cookie*
 Title    Electron Momentum Densities by (y, e y)-Spectroscopy  
 Abstract    We report coincidence measurements of inelastically scattered 148 keV photons and the recoil electrons generated within thin Al and Cu foils. We have analyzed both the Doppler broadening of the scattered photon intensity and the angular correlation of the recoil electron. This corresponds to different scans through the three-dimensional electron momentum density of the target. Estimates of the triple-differential cross-section for Compton scattering are given. The experiment was per-formed with synchrotron radiation from a bending magnet of the DORIS storage ring at DESY, Hamburg. 
  Reference    Z. Naturforsch. 48a, 273—278 (1993); received October 8 1991 
  Published    1993 
  Keywords    Electron momentum densities, Compton scattering, Synchrotron radiation 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0273.pdf 
 Identifier    ZNA-1993-48a-0273 
 Volume    48 
2Author    SudhirA. Kulkarni, ShridharR. GadreRequires cookie*
 Title    On the Topography of Electron Momentum Densities of Linear Molecules  
 Abstract    A topographical study of the electron momentum density (EMD) of some linear molecules is presented with special emphasis on the bond-directionality principle. A new approach to the bond-directionality (BD) principle has been proposed. This is based on the analysis of curvatures of critical points at p = 0 and elsewhere on the bonding axis. The linear molecules are classified into three broad categories: those which fully obey or disobey the BD principle as well as those which satisfy it only partly. The Laplacian of the EMD at p = 0 has been associated with the quality of the wavefunction via the electron density in the tail region. Also, the similarity in the critical structure of both the EMD and the spherically averaged EMD at the origin is brought out. 
  Reference    Z. Naturforsch. 48a, 145—150 (1993); received January 3 1992 
  Published    1993 
  Keywords    Electron momentum densities, Eigenvalues, Critical points, Topography, Bond direc-tionality 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0145.pdf 
 Identifier    ZNA-1993-48a-0145 
 Volume    48 
3Author    Claudia Blaas, Josef Redinger, Raimund Podloucky, Peter Jonas, Peter SchattschneiderRequires cookie*
 Title    Calculation of Compton Profiles Using a Multipole Expansion of the Momentum Density  
 Abstract    A practical method for the calculation of Compton profiles for cubic systems with O and O h symmetry is presented that is based on a multipole expansion of the electron momentum density (EMD) in terms of cubic harmonics. The central quantities, the expansion coefficients, are deter-mined by a Gaussian-type integration (special directions) over the angular coordinates. From these coefficients the coefficients of an analogous expansion of the Compton profile can be directly calculated, establishing a transparent relationship between the electron momentum density and the Compton profile. This direct relationship offers the possibility of tracing back Compton-profile anisotropics to EMD anisotropics more easily, as demonstrated for MgO and FeAl. 
  Reference    Z. Naturforsch. 48a, 198—202 (1993); received December 24 1991 
  Published    1993 
  Keywords    Compton profile, Electron momentum density, Multipole expansion, MgO, FeAl 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0198.pdf 
 Identifier    ZNA-1993-48a-0198 
 Volume    48 
4Author    M. A. Coplan, J. H. Moore, J. A. TossellRequires cookie*
 Title    (e, 2 e)-Spectroscopy and the Electronic Structure of Molecules. A Short Review with Selected Examples  
 Abstract    The simple plane wave target Hartree-Fock impulse approximation for the (e, 2e) reaction is developed. One result of the approximation is the separation of the expression for the (e, 2e) cross-section into a kinematic factor and a structure factor that contains all of the information about the target. When the target is a molecule, the structure factor can be further separated into atomic terms and a geometric term. This is illustrated for a simple one-electron homonuclear diatomic molecule. Three examples of the application of (e, 2e) spectroscopy to systems of chemical interest are given. They are borazine (inorganic benzene), the methyl siloxanes and the inorganic complex trimethylamine boron trifluoride. 
  Reference    Z. Naturforsch. 48a, 358—370 (1993); received January 30 1992 
  Published    1993 
  Keywords    (e, 2e)-Spectroscopy, Electron momentum spectroscopy, Electron momentum density, Electronic structure 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0358.pdf 
 Identifier    ZNA-1993-48a-0358 
 Volume    48 
5Author    Erich WeigoldRequires cookie*
 Title    Recent Advances in Electron Momentum Spectroscopy  
 Abstract    The flexibility of the (e, 2e) technique or "electron momentum spectroscopy" (EMS) in obtaining information on the electronic structure of atoms, molecules, and solids is demonstrated. High-resolution EMS measurements for argon, including the first measurements of momentum profiles belonging to the 2 P° and 2 D e -manifolds, are used to demonstrate the technique for atomic targets. The d-wave transitions in argon are entirely due to initial-state correlations. The first (e, 2e) measure-ments on an excited target, and also on an oriented target, are discussed. Sodium atoms are pumped to the m, = +1 state of the excited 3p-state by cr + -light from a laser. The (e, 2e) measurements on this excited state are in excellent agreement with the momentum density given by the 3p (m, — 1) Hartree-Fock wavefunction. The recent measurements of the valence-electron momentum distribu-tions for ethyne, as well as some earlier results for water, are used as an example of the application of EMS to the study of molecules. The application of the EMS technique to measure spectral momentum densities in condensed-matter targets is demonstrated by some recent results on amor-phous carbon. 
  Reference    Z. Naturforsch. 48a, 371—389 (1993); received March 28 1992 
  Published    1993 
  Keywords    Electron momentum densities, Electron momentum spectroscopy, Wavefunction map-ping, Binding energies 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0371.pdf 
 Identifier    ZNA-1993-48a-0371 
 Volume    48 
6Author    L. C. Smedskjaer, A. BansilRequires cookie*
 Title    Positron Annihilation Studies of the Electronic Structure and Fermiology of High-Tc Superconductors  
 Abstract    We discuss the application of the positron annihilation angular correlation (ACAR) spectroscopy for investigating the electronic structure and Fermiology of high-T c superconductors, with focus on the YBa 2 Cu 3 O v system where most of the experimental and theoretical work has to date been concentrated. Detailed comparisons between the measured 2 D-ACAR positron spectra and the corresponding band theory predictions show a remarkable agreement (for the normal state), indicat-ing that the electronic structure and Fermi surface of this material is described reasonably by the conventional picture. 
  Reference    Z. Naturforsch. 48a, 398—405 (1993); received January 25 1992 
  Published    1993 
  Keywords    Positron annihilation, Angular correlation of annihilation radiation (ACAR), Electron momentum density, High-T c superconductors 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0398.pdf 
 Identifier    ZNA-1993-48a-0398 
 Volume    48