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1993 (9)
1Author    AlanC. Evans, Jerry Mayers, DavidN. Timms, K. Malcolm, J. CooperRequires cookie*
 Title    Deep Inelastic Neutron Scattering in the Study of Atomic Momentum Distributions  
 Abstract    The electron-volt spectrometer (EVS) at the pulsed neutron source facility (ISIS) is being devel-oped for the study of atomic momentum distributions. Neutrons with energies in the range 1 to 100 eV are incident on the sample, and the time-of-flight (TOF) spectrum of the scattered beam is measured by an array of fixed detectors. A resonant foil difference technique is used to yield a set of TOF spectra for those neutrons scattered into a fixed energy and through fixed angles. Informa-tion on the momentum distribution of the target nuclei can be deduced within an impulse approx-imation in a procedure analogous to that in Compton scattering of electrons by photons. Crystalline compounds containing aligned hydrogen bonds and other hydrogenous compounds are of particular interest owing to the high cross-section of the proton at these neutron energies. With improved statistical accuracy of the data it is anticipated that deviations of the proton's potential from a harmonic potential may be determined. Non-hydrogenous systems have also been investi-gated. A description is given of the basic theory and interpretive method. Data obtained on numer-ous systems are presented and discussed. 
  Reference    Z. Naturforsch. 48a, 425—432 (1993); received December 3 1991 
  Published    1993 
  Keywords    Compton profile, DINS, Neutron momentum 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0425.pdf 
 Identifier    ZNA-1993-48a-0425 
 Volume    48 
2Author    D. N. Timms, M. J. CooperRequires cookie*
 Title    The Electron Momentum Distribution in Lead  
 Abstract    Directional Compton profiles have been measured along the [100], [110] and [111] crystallo-graphic axes in lead using 412 and 59.5 keV y-radiation from 98 Au and Am radioisotope sources, respectively. Both measurements are in mutual agreement and show a small anisotropy, which is just distinguishable within the statistical error. The spherically averaged data have been compared with the predictions of relativistic Hartree-Fock (RHF) and non-relativistic Hartree-Fock (HF) free atom calculations. As expected, the experiment clearly favours the RHF rather than the HF calculation. 
  Reference    Z. Naturforsch. 48a, 343—347 (1993); received January 11 1992 
  Published    1993 
  Keywords    Compton profile, Electron momentum distribution, Relative effects, Lead 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0343.pdf 
 Identifier    ZNA-1993-48a-0343 
 Volume    48 
3Author    Usha Mittal, B. K. Sharma, R. K. Kothari, B. L. AhujaRequires cookie*
 Title    Bremsstrahlung Contribution in Compton Scattering from Heavy Metals  
 Abstract    Theoretical estimates of the spectral distribution and total intensity of the bremsstrahlung (BS) relative to the Compton yield have been determined for photoelectrons liberated in scattering experiments on heavy metals with 60 keV radiation. Whereas the total-intensity calculations are based on the approach of Alexandropoulos et al., the spectral distribution has been computed using the Born approximation along with the Elwert and form factor corrections. These results are compared with another calculation based on the approach of Lee et al. Typical results for Mo, Ta, and W are presented. It is found that the relative contribution of BS from a W target is not trivially small, although K-shell photo-ionisation is not possible at these energies. 
  Reference    Z. Naturforsch. 48a, 348—351 (1993); received December 31 1991 
  Published    1993 
  Keywords    Compton profile, Bremsstrahlung, Born approximation, Photoelectrons, Screened potential 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0348.pdf 
 Identifier    ZNA-1993-48a-0348 
 Volume    48 
4Author    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 
5Author    VedeneH. Schmider, Smith, Wolf WeyrichRequires cookie*
 Title    Hartmut  
 Abstract    A recently developed method for the least-squares reconstruction of one-particle reduced density matrices from one-particle expectation values has been applied to isotropic Compton profiles of neon from the literature. The resulting densities in momentum and position space are compared with the ones obtained from ab-initio calculations. 
  Reference    Z. Naturforsch. 48a, 221—226 (1993); received June 3 1992 
  Published    1993 
  Keywords    Density matrix, Compton profile, Least-squares fit, Atomic orbitals, Reconstruction 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0221.pdf 
 Identifier    ZNA-1993-48a-0221 
 Volume    48 
6Author    S. Manninen, V. Honkimäki, P. SuorttiRequires cookie*
 Title    Anisotropy of the Electron Momentum Distribution in Pyrolytic Graphite Studied Using a WK«! Spectrometer  
 Abstract    A new spectrometer construction based on a high-voltage W-anode x-ray tube has been used to measure the directional Compton profiles of a pyrolytic graphite crystal. Owing to the focusing geometry, the monochromatic WKa t beam is very well collimated, which improves the momentum resolution compared with conventional 241 Am spectrometers, operated almost at the same energy. The experimental anisotropy in the basal plane and in the direction of the c-axis is found to be very close to that of a recent calculation, based on the pseudopotential local-density-functional model. 
  Reference    Z. Naturforsch. 48a, 295—298 (1993); received December 12 1991 
  Published    1993 
  Keywords    Compton profile, Pyrolytic graphite, WKoq-spectrometer, Focusing monochromator, Autocorrelation function 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0295.pdf 
 Identifier    ZNA-1993-48a-0295 
 Volume    48 
7Author    D. L. Anastassopoulos, G. D. PriftisRequires cookie*
 Title    The Asymmetry of the Compton Profiles and its Dependence on the Geometrical Resolution  
 Abstract    The asymmetry of Compton Profiles (CPs) measured with a 60-keV 241 Am source on an Al monocrystal, cut along [111], is reported for three different geometrical resolutions. It is found that the geometry of the spectrometer has a substantial effect on the asymmetry of the CP. The better the geometrical resolution the smaller the asymmetry of the CPs. 
  Reference    Z. Naturforsch. 48a, 299—302 (1993); received December 19 1991 
  Published    1993 
  Keywords    Compton profile, Compton asymmetry, Geometrical resolution, Compton spectros-copy, y-ray spectroscopy 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0299.pdf 
 Identifier    ZNA-1993-48a-0299 
 Volume    48 
8Author    B. L. Ahuja, Anil Gupta, B. K. SharmaRequires cookie*
 Title    Compton Profile of Boron Nitride  
 Abstract    The Compton profile of hexagonal boron nitride has been measured using 59.54 keV gamma rays and a planar Ge detector. The results are compared with theoretical Compton profiles calculated for various ionic arrangements and with those available from a bond orbital model, LCAO and SC canonical HF calculations. The LCAO calculation is in relatively good agreement with the present measurement. 
  Reference    Z. Naturforsch. 48a, 310—314 (1993); received December 31 1991 
  Published    1993 
  Keywords    Compton profile, Electron momentum distribution, Hartree-Fock calculation, Ionic model, Linear combination of atomic orbitals 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0310.pdf 
 Identifier    ZNA-1993-48a-0310 
 Volume    48 
9Author    B. K. SharmaRequires cookie*
 Title    Compton Scattering from Heavier Metals  
 Abstract    The use of Compton scattering in the determination of electronic structure has grown consider-ably in the last two decades. With the advent of synchrotron radiation it has become possible, even with good resolution, to measure several single-crystal orientations to determine three-dimensional electron momentum distributions. Although most of the earlier work has been directed to low-Z materials, in the last few years medium and high-Z metals have also been investigated with this technique. In this paper we present a review of these studies on heavier metals with particular attention to the difficulties encountered. Compton profile measurements from techniques based on energetic ion beams are also considered briefly. 
  Reference    Z. Naturforsch. 48a, 334—342 (1993); received December 31 1991 
  Published    1993 
  Keywords    Compton profiles, Electron momentum distributions, Electronic structure, Brems-strahlung, Ion Compton profile 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-0334.pdf 
 Identifier    ZNA-1993-48a-0334 
 Volume    48