| 1. |
- Vos, M., et al.
(författare)
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Determination of the energy-momentum densities of aluminium by electron momentum spectroscopy
- 1999
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 11:18, s. 3645-3661
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Tidskriftsartikel (refereegranskat)abstract
- The energy-resolved momentum densities of thin polycrystalline aluminium films have been measured using electron momentum spectroscopy (EMS), for both the valence band and the outer core levels. The spectrometer used for these measurements has energy and momentum resolutions of around 1.0 eV and 0.15 atomic units, respectively. These measurements should, in principle, describe the electronic structure of the film very quantitatively, i.e. the dispersion and the intensity can be compared directly with theoretical spectral momentum densities for both the valence band and the outer core levels. Multiple scattering is found to hamper the interpretation somewhat. The core-level intensity distribution was studied with the main purpose of setting upper bounds on these multiple-scattering effects. Using this information we wish to obtain a full understanding of the valence band spectra using different theoretical models of the spectral function. These theoretical models differ significantly and only the cumulant expansion calculation that takes the crystal lattice into account seems to describe the data reasonably well.
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| 2. |
- Sohler, D., et al.
(författare)
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Yrast states of the proton drip line nucleus 106 Sb
- 1999
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993 .- 0556-2813 .- 1089-490X. ; 59:3, s. 1324-1327
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Tidskriftsartikel (refereegranskat)abstract
- Yrast states of [Formula Presented] have been investigated in the [Formula Presented] reaction using in-beam [Formula Presented]-spectroscopic methods and in the [Formula Presented] reaction performing delayed [Formula Presented] and conversion electron studies. A new isomeric state was found at 103 keV with [Formula Presented] The number of states and transitions in the proposed level scheme have been doubled. The experimental results are discussed within the framework of the shell model. © 1999 The American Physical Society.
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| 3. |
- Karlsson, Magnus, 1967, et al.
(författare)
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Geometrically induced non-linear phenomena of the TE11-mode in a rectangular optical waveguide
- 1995
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Ingår i: Physica Scripta. - : IOP Publishing. - 1402-4896 .- 0031-8949. ; 52:3, s. 313-317
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Tidskriftsartikel (refereegranskat)abstract
- Retaining all significant terms of Maxwell equations, we derive a gener-alized governing equation for waves in a Kerr-nonlinear, rectangulai optical waveguide. As a specific example, we show that the field com-ponents of the TEn-mode in such a waveguide will achieve oscillations in both amplitude and phase during propagation. The nonlinearity appeal only in a characteristic length scale of these phenomena, whereas tht overall properties of the oscillations are determined by the waveguidt geometry.
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| 4. |
- Kawamura, J., et al.
(författare)
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Low noise NbN lattice-cooled superconducting hot-electron bolometric mixers at submillimeter wavelengths
- 1997
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 70:12, s. 1619-1621
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Tidskriftsartikel (refereegranskat)abstract
- Lattice-cooled superconducting hot-electron bolometric mixers are used in a submillimeter-wave waveguide heterodyne receiver. The mixer elements are niobium nitride film with 3.5 nm thickness and ∼ 10 μm2 area. The local oscillator power for optimal performance is estimated to be 0.5 μW, and the instantaneous bandwidth is 2.2 GHz. At an intermediate frequency centered at 1.4 GHz with 200 MHz bandwidth, the double sideband receiver noise temperature is 410 K at 430 GHz. The receiver has been used to detect molecular line emission in a laboratory gas cell.
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| 5. |
- Fjelstad, Jens, 1971-, et al.
(författare)
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Equivalence of Chern-Simons gauge theory and WZNW model using a BRST symmetry
- 1999
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Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 466:2-4, s. 227-233
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Tidskriftsartikel (refereegranskat)abstract
- The equivalence between the Chern-Simons gauge theory on a three-dimensional manifold with boundary and the WZNW model on the boundary is established in a simple and general way using the BRST symmetry. Our approach is based on restoring gauge invariance of the Chern-Simons theory in the presence of a boundary. This gives a correspondence to the WZNW model that does not require solving any constraints, fixing the gauge or specifying boundary conditions.
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| 6. |
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| 7. |
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| 8. |
- 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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| 9. |
- Nilsson, Thomas, 1965
(författare)
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Excursions Along the Drip Line
- 1995
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The drip lines are the outer boundaries of the chart of the nuclides, terminating the isobaric chains on both sides of the valley of .beta.-stability with respect to stability against particle emission. The neutron drip line is, at the moment, only experimentally accessible for the very lightest elements. When approaching the neutron drip line, the structure of the nuclei starts to show anomalies compared to stable nuclei. The best known case is 11Li, having an extremely dilute structure with two loosely bound neutrons surrounding a 9Li core with normal density. This kind of configuration has been labelled a neutron halo and can be found in several nuclei along the drip line. This work regards experimental studies of drip-line nuclei through dissociation reactions at high beam energies and spectroscopy of .beta.-delayed particles. The effect of cross-talk between neutron detectors has been measured and compared to the results of a simulation code. The measurements confirmed the validity of the code and showed a negligible contribution of cross-talk for the neutron-detector arrays used in experiments at GANIL. The .beta.-delayed charged particles following the precursors 6,8He have been studied at ISOLDE, CERN with a newly developed gas-detector telescope. The branching ratios for .beta.-delayed deuteron emission from 6He and .beta.-delayed triton emission from 8He were measured with improved accuracy and decreased low-energy cut-off compared to earlier experiments. In an experiment at GSI, dissociation of 8He, 11Li and 11Be, with energies of 240 MeV/u, 280 MeV/u and 460 MeV/u respectively, was studied. From the experimental data, cross sections and momentum distributions could be extracted. The reaction mechanisms could be probed by studying various reaction channels, revealing an invariability regarding the width of the neutron momentum distribution when concentrating upon the core-breakup reactions. The role of the unbound resonance 10Li has been elucidated by population through one-neutron stripping from 11Li and one-proton stripping from 11Be. The longitudinal and transverse momentum distributions from the reaction 11Li -> 9Li + X have been measured at the same beam energy. The widths were found to be identical, and the lack of Coulomb broadening in the transverse case indicates that the halo-removal reactions predominantly take place at large impact parameters.
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| 10. |
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