| 1. |
- Svensson, C. E., et al.
(författare)
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Decay Out of the Doubly Magic Superdeformed Band in the N=Z Nucleus 60Zn
- 1999
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Ingår i: Physical Review Letters. - 1079-7114. ; 82:17, s. 3400-3403
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Tidskriftsartikel (refereegranskat)abstract
- The doubly magic superdeformed band in the N = Z nucleus Zn-60 has been identified. Linking transitions connecting this band to the yrast line provide the first spin, parity, and excitation energy measurements for superdeformed states in the A similar to 60 region. The stretched-E2 character and relatively large B(E2) values of these transitions suggest a nonstatistical decay-out process.
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| 2. |
- De Angelis, G., et al.
(författare)
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Collective Excitations in the Vicinity of N=Z
- 1999. - 1 SUPPL. 1
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Ingår i: Proceedings INPC 1998. - 0375-9474. ; 654, s. 659-662
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Konferensbidrag (refereegranskat)abstract
- In our contribution to the INPC98 conference we reported on the experimental investigation of high spin collective states in medium and heavy mass N≈Z nuclei at LNL. The main purpose is to set light on the role of the proton-neutron interaction in the collective behavior of the nucleus. In medium mass N=Z nuclei, in contrast with the stable nuclei, valence protons and neutrons occupy the same orbitals and one may expect a reinforcement of neutron-proton T=0 (np) pairing correlations[1]. In this interesting subject, the medium mass N=Z=36 72Kr has been studied and completely reported in [2]. In this proceedings we will concentrate in unpublished results concerning the onset of collectivity on nearly spherical nuclei in the 100Sn region. In nuclei with Z=50 and Z=49 dipole bands have been found indicating the presence of "Magnetic Rotation" [3].
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| 3. |
- Gadea, A., et al.
(författare)
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Spectroscopy at N=Z with EUROBALL III
- 1999
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 495, s. 195-198
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Konferensbidrag (refereegranskat)abstract
- A complete study of the nuclear structure by means of gamma spectroscopy requires, in addition to the high resolution gamma measurement and accurate DCO's or angular distributions, the information concerning the Electric or Magnetic character of the transition. This information for transitions in nuclei far from stability valley is now reachable in the new generation of Ge-arrays based in composite detectors. EUROBALL III is a good example with the high polarization sensitivity of the 90 degrees ring of Clovers. The Polarization correlations PCO's measured in coincidence with the Cluster detectors permits to investigate transitions in weakly populated nuclei. In this contribution we present results on medium mass N=Z nuclei measured with EUROBALL III coupled with light particle ancillary detectors.
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| 4. |
- Svensson, C. E., et al.
(författare)
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Smooth Termination of Rotational Bands in 62Zn: Evidence for a Loss of Collectivity
- 1998
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Ingår i: Physical Review Letters. - 1079-7114. ; 80:12, s. 2558-2561
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Tidskriftsartikel (refereegranskat)abstract
- Two sets of strongly coupled rotational bands have been identified in Zn-62. These bands have been observed up to the terminating states of their respective configurations. Lifetime measurements indicate that the transition quadrupole moments in these bands decrease as termination is approached. These results establish the first terminating states of rotational bands in the A similar to 60 mass region and confirm the predicted loss of collectivity associated with smooth band termination.
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| 5. |
- de, Angelis G, et al.
(författare)
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Rotation induced octupole correlations in the neutron-deficient Te-109 nucleus
- 1998
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Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 437:3-4, s. 236-242
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Tidskriftsartikel (refereegranskat)abstract
- High spin states in the neutron deficient nucleus 109Te have been populated with the 58Ni+54Fe reaction at 220 MeV and investigated through γ-spectroscopy methods at the GASP spectrometer making use of reaction channel selection with the ISIS Si-ball. The level scheme has been extended up to an excitation energy of ≈12.1 MeV. The spins and parities of the observed levels are assigned tentatively supporting the identification of two bands of opposite parity connected by strong dipole transitions inferred to be of E1 character. Octupole correlations in 109Te induced by rotation are suggested as the cause of this effect.
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| 6. |
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| 7. |
- Rudolph, Dirk, et al.
(författare)
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Shell-model Influence in the Rotational Nucleus 86Mo
- 1996
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 54:1, s. 117-124
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in Mo-86 were studied by means of the fusion evaporation reaction Ni-58(S-32,2p2n) Mo-86 at 135 MeV beam energy. Charged-particle-gamma gamma and -gamma gamma gamma coincidences recorded with the early implementation of the GAMMASPHERE array and the MICROBALL charged-particle detection system were used to largely extend the level scheme of the T-tau=1 nucleus Mo-86 to a possible spin of I=24h at 13 MeV excitation energy. The excitation scheme is compared to neighboring nuclei. There is evidence for enhanced shell-model influence in the 4 quasiparticle region (I=12-16h). The observed (pi=+,alpha=0) sequence at spin I greater than or equal to 16 h appears to be associated with a triaxial collective rotational band. This interpretation is supported by calculations within the configuration-dependent shell-correction approach with the cranked Nilsson potential.
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| 8. |
- Svensson, C. E., et al.
(författare)
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Observation and Quadrupole Moment Measurement of the First Superdeformed Band in the A~60 Mass Region
- 1997
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Ingår i: Physical Review Letters. - 1079-7114. ; 79:7, s. 1233-1236
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Tidskriftsartikel (refereegranskat)abstract
- A high-spin rotational cascade of six gamma rays has been observed in Zn-62. The quadrupole moment of 2.7(-0.5)(+0.7) e b measured for this band corresponds to a deformation beta(2) = 0.45(-0.07)(+0.10). The properties of this band are in excellent agreement with calculations that predict high-spin superdeformed bands in Zn-62 with deformations beta(2) = 0.41-0.49. These results establish a new region of superdeformation for nuclei with neutron and proton numbers N, Z approximate to 30-32.
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| 9. |
- Yu, C. H., et al.
(författare)
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Comparison of Superdeformed Bands in 61Zn and 60Zn: Possible Evidence for T=0 Pairing
- 1999
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 60:3
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Tidskriftsartikel (refereegranskat)abstract
- The yrast superdeformed band in Zn-61 has been established using Si-28(Ar-36, 2pn)Zn-61 and Ca-40(Si-29, 2 alpha)Zn-61 fusion-evaporation reactions. The excitation energy of this band was determined via two transitions that link this band to the normally deformed states. Lifetime analysis of this band resulted in a quadrupole moment of Q(t) = 3.0 +/- (0.5)(0.4)e b, which corresponds to a deformation of beta(2) = 0.50+/-(0.07)(0.06). A comparison of the J((2)) dynamical moments of inertia of the yrast superdeformed band in Zn-61 with those in Zn-60 shows a nearly complete blocking of the observed alignment in Zn-60, indicating that T=0 proton-neutron pair correlations may be present in Zn-60. [S0556-2813(99)51109-6].
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| 10. |
- Devlin, M., et al.
(författare)
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Superdeformation in 68Zn: Evidence for a New, Neutron-rich Island of Superdeformation in A~70 Nuclei
- 1999
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Ingår i: Physical Review Letters. - 1079-7114. ; 82, s. 5217-5220
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Tidskriftsartikel (refereegranskat)abstract
- A superdeformed rotational structure is reported in the stable nucleus Zn-68. It has a transition quadrupole moment (Q(t)) of 2.5(-0.4)(+0.7) e b (beta(2) approximate to 0.4), as measured by the residual Doppler shift method. Theoretical calculations suggest that two different configurations are possible candidates for this band. One is built without h(11/2) neutrons, as seen in superdeformed bands in the A similar to 60 region, while the other involves one h(11/2) neutron in analogy with superdeformed bands in the A similar to 80 region. The second of these candidate configurations is preferred, thus establishing a new, neutron-rich (relative to the line of beta stability) region of superdeformation with Z similar to 30 and N similar to 38.
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| 11. |
- Sun, H., et al.
(författare)
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New Band Structures and an Unpaired Crossing in 78Kr
- 1999
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 59:2, s. 655-664
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in Kr-78 were studied using the Ni-58(Na-23,3p) reaction at 70 MeV and the Ni-58(Si-23,alpha 4p) reaction at 130 MeV. Prompt gamma-gamma coincidences were measured using the Pitt-FSU detector array and the GAMMASPHERE-MICROBALL array. Results from these experiments have led to 26 new excitation levels, some of which have been grouped into 3 new bands. Spins were assigned based on directional correlations of oriented nuclei. Two of the new negative-parity bands appear to form a signature-partner pair based on a two-quasineutron structure, in contrast to the previously known two-quasiproton negative-parity bands. A forking has been observed at the 24(+) state in the yrast band, which calculations suggest may result from an unpaired crossing. The available evidence suggests oblate shapes in the yrast band coexist with prolate shapes in the negative-parity bands. [S0556-2813(99)04602-6].
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| 12. |
- Andersson, T., et al.
(författare)
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High-spin States in the A=39 Mirror Nuclei 39Ca and 39K
- 1999
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - 1434-6001. ; 6, s. 5-8
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states of the mass A = 39 mirror pair K-39 and Ca-39 were investigated via the fusion-evaporation reaction Si-28+O-16 at 125 MeV beam energy. The GAMMASPHERE array in conjunction with the 4 pi charged-particle detector array MICROBALL and neutron detectors was used to detect gamma rays in coincidence with evaporated light particles. The results of the first high-spin study of the T-z = -1/2 nucleus Ca-39 are discussed in terms of mirror symmetry and compared to spherical shell-model calculations in the 1d(3/2)-1f(7/2) configuration space.
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| 13. |
- LaFosse, D R, et al.
(författare)
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Search for hyperdeformation in Gd-146,Gd-147
- 1996
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 54:4, s. 1585-1588
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Tidskriftsartikel (refereegranskat)abstract
- A search was undertaken to look for evidence of hyperdeformation in Gd-146,Gd-147. Three experiments employing Gammasphere for gamma-ray detection coupled with the Microball for channel selection via charged particle detection were carried out with increasing detection sensitivity and statistics. No definitive evidence for band structures that could be assigned to hyperdeformation could be found. Candidates previously reported are shown not to have properties consistent with a band structure.
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| 14. |
- Rudolph, D, et al.
(författare)
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Multiparticle-hole states of high spin in N < 50, A ≈ 90 nuclei : 1. The transitional nucleus 4389Tc46
- 1995
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 587:1, s. 181-201
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Tidskriftsartikel (refereegranskat)abstract
- High spin states in the nucleus 89Tc have been studied via the fusion evaporation reaction 58Ni(40Ca,2αp)89Tc at 180 MeV beam energy. The NORDBALL γ-ray spectrometer equipped with auxiliary detectors for light particle selection was used to measure γγ- and particle-γγ coin-cidences. Some 60 transitions were placed into a level scheme comprising 38 levels reaching up to 9.2 MeV excitation energy and a possible spin of . The level scheme is compared to those of neighbouring nuclei and interpreted in terms of the spherical shell model. The calculations were performed with different sets of parameters within a restricted , , and configuration space. States above 2.3 MeV excitation energy are well reproduced by shell model calculations based on an empirical residual interaction, whereas collective excitations are suggested to contribute to the wave functions of lower lying states.
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| 15. |
- Rudolph, Dirk, et al.
(författare)
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Rotational Bands in the Doubly Magic Nucleus 56Ni
- 1999
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Ingår i: Physical Review Letters. - 1079-7114. ; 82:19, s. 3763-3766
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Tidskriftsartikel (refereegranskat)abstract
- Structures of the medium- to high-spin states in the doubly magic nucleus Ni-56 have been investigated using the reaction Si-28(Ar-36, 2 alpha) and the gamma-ray spectrometer Gammasphere in conjunction with the 4 pi charged-particle detector array Microball. Two well-deformed rotational bands have been identified. There is evidence that one of the bands, which is identical to a sequence in the odd-odd neighbor Cu-58, partially decays via proton emission into the ground state of Co-55. Predictions of extensive large-scale shell-model and cranked Hartree-Fock and Hartree-Fock-Bogolyubov calculations are compared with the experimental data.
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