| 1. |
- Algora, A., et al.
(författare)
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Pronounced Shape Change Induced by Quasiparticle Alignment
- 2000
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813 .- 1089-490X. ; 61:3
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Tidskriftsartikel (refereegranskat)abstract
- Mean lifetimes of high-spin states of Kr-74 have been determined using the Doppler-shift attenuation method. The high-spin states were studied using the Ca-40(Ca-40, alpha 2p) reaction at a beam energy of 160 MeV with the GASP gamma-ray spectrometer. The ground-state band and negative parity side band show the presence of three different configurations in terms of transitional quadrupole deformations. A dramatic shape change was found along the ground-state band after the S-band crossing. The deduced quadrupole deformation changes are well reproduced by cranked Woods-Saxon Strutinsky calculations.
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| 2. |
- Andreyev, A. N., et al.
(författare)
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In-beam and alpha-decay spectroscopy of Po-191 and evidence for triple shape coexistence at low energy in the daughter nucleus Pb-187
- 2002
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 66:1
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Tidskriftsartikel (refereegranskat)abstract
- Prompt gamma rays have been observed for the first time from the neutron-deficient nucleus Po-191 using the recoil-decay tagging technique at the RITU gas-filled separator. In addition improved alpha decay data have been measured for Po-191 and its daughter product Pb-187. The complementary gamma- and alpha-decay data point to the onset of oblate deformation in the light odd-mass Po nuclei by approaching the neutron midshell at N=104. The pattern of the favored and unfavored states observed on top of the 13/2(+) isomer in Po-191 indicates a change from the weak-coupling towards the strong-coupling scheme in Po-191m. In the daughter nucleus Pb-187, the 13/2(+) and 3/2(-) isomeric states become degenerate within the experimental accuracy. Evidence for triple shape coexistence at low energy has been found in the high-spin isomer in Pb-187. The results are supported by potential-energy surface calculations and by particle-plus-rotor calculations.
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| 3. |
- Andreyev, A. N., et al.
(författare)
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Shape-changing particle decays of Bi-185 and structure of the lightest odd-mass Bi isotopes
- 2004
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69:5, s. 054308-
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Tidskriftsartikel (refereegranskat)abstract
- Proton and alpha decay of the proton-rich nuclide Bi-185 has been restudied in more detail in the complete fusion reaction Nb-93(Mo-95, 3n)Bi-185 at the velocity filter SHIP. The observed decay pattern of Bi-185 and of the heavier odd-mass isotopes Bi-187,Bi-189,Bi-191,Bi-193 are interpreted based on potential-energy surface calculations. It is shown that the experimental systematics of the particle decays and of the excited states in these nuclei (where known) can be explained by the prolate-oblate shape co-existence at low excitation energy. The observed state in Bi-185 is proposed to be of prolate nature, which is in contrast with the previously proposed oblate interpretation.
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| 4. |
- Asztalos, S. J., et al.
(författare)
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Isotopic yields of neutron-rich nuclei from deep-inelastic reactions
- 2000
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 6101:1
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Tidskriftsartikel (refereegranskat)abstract
- We follow up on our earlier work involving a light projectile (Ca-48) to populate high spin states in neutron-rich nuclei with results from experiments involving a heavier projectile (Sm-154) fur the purposes of studying isotopic yields. These yields, which in some cases were mensurable down to a level of 0.1 of the total reaction cross section, are presented from three separate reactions. A trend in the isotopic yields towards N/Z equilibration is observed in one experiment having a large disparity in N/Z ratios between the projectile and target. In the two other reactions, where the N/Z driving force is less pronounced, the yields are instead clustered around the projectile and target nuclei. We present correlated projectilelike and targetlike fragment isotopic yields derived from gamma-gamma coincidences, a technique that enables one to partition the yield of an isotope according to the amount of neutron evaporation. Using this method we find that for the zero-neutron evaporation channel transfer occurs predominantly into the light fragment, consistent with the nature of the deep-inelastic mechanism. We further find that multiple-neutron evaporation contributes substantially to the yields of the isotopes.
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| 5. |
- Ban, Shufang, et al.
(författare)
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Density dependencies of interaction strengths and their influences on nuclear matter and neutron stars in relativistic mean field theory
- 2004
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69:4
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Tidskriftsartikel (refereegranskat)abstract
- The density dependencies of various effective interaction strengths in the relativistic mean field are studied and carefully compared for nuclear matter and neutron stars. The influences of different density dependencies are presented and discussed on mean field potentials, saturation properties for nuclear matter, equations of state, maximum masses, and corresponding radii for neutron stars. Though the interaction strengths and the potentials given by various interactions are quite different in nuclear matter, the differences of saturation properties are subtle, except for NL2 and TM2, which are mainly used for light nuclei, while the properties by various interactions for pure neutron matter are quite different. To get an equation of state for neutron matter without any ambiguity, it is necessary to constrain the effective interactions either by microscopic many-body calculations for the neutron matter data or the data of nuclei with extreme isospin. For neutron stars, the interaction with large interaction strengths give strong potentials and large Oppenheimer-Volkoff (OV) mass limits. The density-dependent interactions DD-ME1 and TW-99 favor a large neutron population due to their weak rho-meson field at high densities. The OV mass limits calculated from different equations of state are 2.02-2.81M, and the corresponding radii are 10.78-13.27 km. After the inclusion of the hyperons, the corresponding values become 1.52-2.06M and 10.24-11.38 km.
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| 6. |
- Blazhev, A., et al.
(författare)
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Observation of a core-excited E4 isomer in Cd-98
- 2004
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69
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Tidskriftsartikel (refereegranskat)abstract
- A core-excited I-pi=(12(+)) spin-gap isomer was identified in Cd-98 in an experiment at EUROBALL IV. It was found to feed the known I-pi=(8(+)) seniority isomer by an E4 transition. Half-lives of T-1/2=0.23 ((+4)(-3)) mus and 0.17 ((+6)(-4)) mus were measured for the two states at E-x=6635 keV and 2428 keV, respectively. From the excitation energy of the core-excited isomer a Sn-100 shell gap of 6.46(15) MeV is inferred. The measured E4 and E2 strengths, Sn-100 core excitations and the origin of empirical polarization charges are discussed in the framework of large-scale shell model calculations. An E2 polarization charge for protons of deltae(pi)
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| 7. |
- Blideanu, V., et al.
(författare)
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Nucleon-induced reactions at intermediate energies : New data at 96 MeV and theoretical status
- 2004
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 70:1, s. 014607-
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Tidskriftsartikel (refereegranskat)abstract
- Double-differential cross sections for light charged particle production (up to A=4) were measured in 96 MeV neutron-induced reactions, at the TSL Laboratory Cyclotron in Uppsala (Sweden). Measurements for three targets, Fe, Pb, and U, were performed using two independent devices, SCANDAL and MEDLEY. The data were recorded with low-energy thresholds and for a wide angular range (20°–160°). The normalization procedure used to extract the cross sections is based on the np elastic scattering reaction that we measured and for which we present experimental results. A good control of the systematic uncertainties affecting the results is achieved. Calculations using the exciton model are reported. Two different theoretical approaches proposed to improve its predictive power regarding the complex particle emission are tested. The capabilities of each approach is illustrated by comparison with the 96 MeV data that we measured, and with other experimental results available in the literature.
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| 8. |
- Bruce, A. M., et al.
(författare)
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Two-neutron alignment and shape changes in As-69
- 2000
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 6202:2
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Tidskriftsartikel (refereegranskat)abstract
- The nucleus As-69 was Studied using the Ca-40(S-32,3p)As-69 reaction at a beam energy of 105 MeV. An extension of the band built on the g(9/2) orbital was observed to exhibit a band crossing at a rotational frequency of 0.511 MeV with an associated alignment of 7 (h) over bar. This alignment is interpreted as being due to a pair of g(9/2) neutrons. Total Routhian surface calculations have been carried out which confirm that the shape of this nucleus changes from oblate at low spin to a triaxial prolate shape at intermediate spin.
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| 9. |
- Daehnick, W.W, et al.
(författare)
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Spin correlations in polarized p polarized p -> p n pi+ production near threshold
- 2002
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Ingår i: Physical Review C. Nuclear Physics. - : American Physical Society. - 0556-2813 .- 1089-490X. ; 65, s. 024003-1
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Tidskriftsartikel (refereegranskat)abstract
- A first measurement of longitudinell as well as transverse spin correlation coefficients for the reaction pp->pn pi+ is made using a polarized proton target and a polarized proton beam. We report kinematically complete measurements for this reaction at 32
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| 10. |
- Delion, D. S., et al.
(författare)
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High-spin proton emitters in odd-odd nuclei and shape changes
- 2003
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 68:5, s. 054603-
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Tidskriftsartikel (refereegranskat)abstract
- We present a formalism to describe proton emission from odd-odd nuclei based on a scatteringlike approach. Special emphasis is given to the case of transitions between states with different deformations. As an example we estimate the proton half-life of the odd-odd nucleus Cu-58 . Our calculations show that the change of deformation in the decay process has a significant influence on the half life. In addition, the angular momentum coupling of proton and neutron orbitals can result in an additional K hindrance of the decay. To fully account for the observed half life in Cu-58 , we propose shape mixing of the final state.
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