| 1. |
- Hamamoto, Ikuko, et al.
(författare)
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Form-factor of low-lying Kπ=1+ excitations in rare-earth nuclei
- 1987
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 194:1, s. 6-10
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Tidskriftsartikel (refereegranskat)abstract
- The differential cross section of inelastic electron scattering for the low-lying “collective” Kπ=1+ excitations in rare-earth nuclei is calculated in DWBA by using microscopically calculated transition-densities. In the region of low-momentum transfer (q⪅0.5 fm-1) in which experimental data are available the shape of calcualted cross sections is almost the same for all nuclei and is slightly but systematically different from the observed shape.
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| 2. |
- Adiels, Lars, et al.
(författare)
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A π0 and η spectrometer of lead glass and BGO for momenta up to 1 GeV/c
- 1986
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 244:3, s. 380-390
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Tidskriftsartikel (refereegranskat)abstract
- A spectrometer consisting of two sets of bismuth germanium oxide (BGO) crystals and a lead-glass array has been used to measure the [pi]0 and [eta] momentum spectra produced from proton-antiproton annihilations at rest. We describe the test of the BGO sets in electron beams of energies from 50 to 450 MeV. We discuss the method of construction and calibration of the lead-glass array, as well as procedures to extract the energy and position resolutions for detected photons. A momentum resolution ([sigma]) for [pi]0’s and [eta]’s of 4% and 3%, respectively has been achieved at momenta below 1 GeV/c.
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| 3. |
- Adiels, L, et al.
(författare)
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Some results of experiment PS182 at LEAR
- 1986
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Ingår i: Antiproton 86. - Singspore : World Scientific Publishing. - 9971503131 ; , s. 199-204, s. 199-204
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Magnusson, Charlotte
(författare)
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The effect of the presence of quadrupole pairing on the properties of Kπ = 1+ states in doubly even nuclei
- 1991
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 43:5, s. 460-468
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Tidskriftsartikel (refereegranskat)abstract
- The influence of a quadrupole pair interaction on Kπ = 1+ states in rare earth nuclei is investigated using the Quasiparticle Random Phase Approximation. Comparison of the obtained results with available experimental data indicates a rather weak quadrupole pair interaction in these nuclei. The calculation of the B(M1) strength is extended to higher energies to account for the recently observed higher lying M1-strength. The differential cross section of inelastic electron scattering is calculated within DWBA for lower lying Kπ = 1+ states and is seen to be consistent with the interpretation that the observed states around 3 MeV are of isovector convection current character and have their main M1-strength coming from natural parity proton components.
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| 5. |
- Chen, W., et al.
(författare)
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Electronic and geometric structure of clean Pt3Ti(111)
- 1994
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Ingår i: Physical Review B. - 0163-1829 .- 1095-3795. ; 50:8, s. 5620-5627
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Tidskriftsartikel (refereegranskat)abstract
- Photoemission spectra and scanning tunneling microscopy (STM) images of the clean Pt3Ti(111) surface are presented. Grazing-emission core-level spectra show that the topmost layer is pure platinum, modified compared with the Pt(111) surface. The Pt 4f levels at the surface are shifted 0.4 eV toward the Fermi level relative to bulk Pt3Ti while the Pt 4f and Ti 2p levels in the bulk are shifted 0.4 and 1.3 eV to higher binding energy relative to pure bulk platinum and titanium, respectively, Tunneling measurements show a surface with only metallic atoms and a small p(2×2) buckling. Our observations of molecularly adsorbed CO are not compatible with metallic titanium atoms at the surface and the STM data thus indirectly confirm that only platinum atoms are present in the topmost layer. Linear muffin-tin-orbital calculations of the bulk band structure and valence-band photoemission spectra reveal highly hybridized electron states between the Pt d and Ti d levels. The calculations give a minor charge transfer from Ti to Pt, 0.37 electrons per Ti atom, but the large core-level shifts reflect the stability of the alloy and the response to the excitation rather than the amount of charge transfer. The observed segregation of platinum to the surface and the altered electronic structure of the topmost layer, due to interaction with the underlying alloy, are in full agreement with earlier conclusions based on low-energy electron-diffraction measurements and on the chemical properties of the surface. © 1994 The American Physical Society.
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| 6. |
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| 7. |
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| 8. |
- Gevorgian, Spartak, 1948, et al.
(författare)
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The Optical Power Distribution and Scattering Losses in Symmetric Channel Waveguide X-Junction
- 1991
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Ingår i: Optical and Quantum Electronics. - 0306-8919 .- 1572-817X. ; 23, s. 649-656
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Tidskriftsartikel (refereegranskat)abstract
- It is shown theoretically and experimentally that there is sufficient light radiation at the crossing points of wave-guides, and sufficient coupling between input branches and output branches of integrated optic symmetric crossing channel wave-guides. For straight X-junctions the crosstalk could be changed in a wide range varying the crossing angle, while for widened X-junction with a fixed crossing angle the crosstalk could be changed by varying the length of the central straight waveguide section.
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| 9. |
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| 10. |
- Karlsson, Krister, 1961-
(författare)
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Electronic Structure Calculations: Materials with Weak and Strong Correlations
- 1992
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is devoted to studies of various electronic properties which can be extracted from photoemission spectroscopy. Both weakly and strongly correlated systems are discussed, ranging from free electron metal surfaces to strongly correlated copper oxide compounds. In order to study such a variety of systems, different calculational schemes have to be employed. This work is mainly based on band structure calculations using the local density approximation. However, for strongly correlated systems the need for model Hamiltonians is crucial. Subjects discussed are: * inverse photoemission spectra from the Cd(0001) surface obtained by a multiple scattering formalism. The results are in good agreement with recent experimental data. Especially, the one-step model is used to demonstrate image states excitations by secondary beams. * artificial structures, such as semiconductor heterojunctions and short-period superlattices, which are of vital importance for modern electronic devices. A method for tuning the band offset at semiconductor interfaces is proposed; by varying (n,m) for the GaAs/(AlAs)n(GaAs)m interface, the magnitude of the valence band offset can be designed. The metallic superlattice Mo/V was also studied, with emphasis on the application of hydrogen storage. * Schottky barrier heights. Final state screening effects can influence the Schottky barrier height, as deduced from measured core level shifts. According to our calculations, such effects may be of the order 0.1-0.2 eV. * chemical shifts in Cu2O, CuO and NaCuO2, where the Cu atom is formally mono-, di- and trivalent. We find similar chemical shifts between Cu atoms in YBa2Cu3O6.5 as between the Cu atoms in the model compounds. This suggests that different Cu atoms in YBa2Cu3O6.5 are formally mono-, di- and trivalent. The Cu 2p core level spectra were calculated using the Anderson impurity model, with parameters obtained from ab initio calculations. The results are related to the formal valence of Cu, and can be explained by a charge counting argument.
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