| 1. |
- Niedermaier, O., et al.
(author)
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"Safe" Coulomb excitation of Mg-30
- 2005
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 94:17, s. 172501 (artno)-
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Journal article (peer-reviewed)abstract
- We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient γ spectrometer MINIBALL. Using Mg-30 ions accelerated to an energy of 2.25 MeV/u together with a thin Ni-nat target, Coulomb excitation of the first excited 2(+) states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative deexcitation γ-ray yields the B(E2;0(gs)(+)→ 2(1)(+)) value of Mg-30 was determined to be 241(31)e(2) fm(4). Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope Mg-30 resides outside the "island of inversion."
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| 2. |
- Niedermaier, O., et al.
(author)
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The neutron-rich Mg isotopes: first results from MINIBALL at REX-ISOLDE
- 2005
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In: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 752, s. 273-273
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Journal article (peer-reviewed)abstract
- We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient γ spectrometer MINIBALL. Using Mg-30 ions accelerated to an energy of 2.25 MeV/u together with a thin Ni-nat target, Coulomb excitation of the first excited 2(+) states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative deexcitation γ-ray yields the B(E2;0(gs)(+)→ 2(1)(+)) value of Mg-30 was determined to be 241(31)e(2) fm(4). Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope Mg-30 resides outside the "island of inversion."
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| 3. |
- Scheit, H., et al.
(author)
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Coulomb excitation of neutron-rich beams at REX-ISOLDE
- 2005
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In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 25:Suppl. 1, s. 397-402
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Conference paper (peer-reviewed)abstract
- After the successful commissioning of the radioactive beam experiment at ISOLDE (REX-ISOLDE) - an accelerator for exotic nuclei produced by ISOLDE - in 2002 and the promotion to a CERN user facility in 2003, first physics experiments using these beams were performed. Initial experiments focused on the region of deformation in the vicinity of the neutron-rich Na and Mg isotopes. Preliminary results on the neutron-rich Na and Mg isotopes show the high potential and physics opportunities offered by the exotic isotope accelerator REX in conjunction with the modern Germanium gamma spectrometer MINIBALL.
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| 4. |
- Bouchet, P., et al.
(author)
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The Mid-Infrared Instrument for the James Webb Space Telescope, III: MIRIM, The MIRI Imager
- 2015
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In: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 127:953, s. 612-622
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Journal article (peer-reviewed)abstract
- In this article, we describe the Mid-Infrared Imager Module (MIRIM), which provides broadband imaging in the 5-27 mu m wavelength range for the James Webb Space Telescope. The imager has a 0 ''.11 pixel scale and a total unobstructed view of 74 '' x 113 '' The remainder of its nominal 113 '' x 113 '' field is occupied by the coronagraphs and the low-resolution spectrometer. We present the instrument optical and mechanical design. We show that the test data, as measured during the test campaigns undertaken at CEA-Saclay, at the Rutherford Appleton Laboratory, and at the NASA Goddard Space Flight Center, indicate that the instrument complies with its design requirements and goals. We also discuss the operational requirements (multiple dithers and exposures) needed for optimal scientific utilization of the MIRIM.
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| 5. |
- Lagergren, K, et al.
(author)
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Evidence for excited states in Ag-95
- 2002
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In: European Physical Journal A. - : Springer. - 1434-6001 .- 1434-601X. ; 14:4, s. 393-396
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Journal article (peer-reviewed)abstract
- The first evidence for excited states in Ag-95 is presented. Ag-95 is the heaviest T-z = 1/2 nucleus for which gamma-rays have been identified. The reaction Ca-40(Ni-58, 1p2n)Ag-95 was used in the experiment, which resulted in the assignment of three gamma-rays to Ag-95. A detector system consisting of the detector arrays Euroball, Neutron Wall and Euclides was used to detect gamma-rays, neutrons and charged particles, respectively.
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| 6. |
- Karlgren, Daniel, et al.
(author)
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High-angular-momentum structures in Zn-64
- 2004
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In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69, s. 1-034330
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Journal article (peer-reviewed)abstract
- High-angular-momentum states in Zn-64 were populated in the Ca-40(Si-28,4p) reaction at a beam energy of 122 MeV. Evaporated, light, charged particles were identified by the Microball, while gamma rays were detected using the Gammasphere array. The main focus of this paper is on two strongly coupled, collective bands. The yrast band, which was previously known, has been linked to lower-lying states establishing the excitation energies and angular momenta of in-band states for the first time. The newly identified excited band decays to the yrast band but firm angular-momentum assignments could not be made. In order to interpret these structures cranked-Nilsson-Strutinsky calculations have been performed. The calculations have been extended to account for the distribution of nucleons within a configuration. The yrast collective band is interpreted as based on the pi(f(7/2))(-1)(p(3/2)f(5/2))(2)(g(9/2))(1)nu(p(3/2)f(5/2))(4)(g(9/2))(2) configuration. There are several possible interpretations of the second band but it is difficult to distinguish between the different possibilities.
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| 7. |
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| 8. |
- Rudolph, Dirk, et al.
(author)
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The 3701 keV Neutron g9/2 Single-particle State in 57Ni
- 1999
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In: European Physical Journal A. Hadrons and Nuclei. - 1434-6001. ; 6, s. 377-380
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Journal article (peer-reviewed)abstract
- The neutron g(9/2) single-particle state in Ni-57 has been unambiguously identified in a combined measurement of the linear polarization, angular distribution, and angular correlation of gamma rays following the fusion-evaporation reaction Si-28(S-32,2pn)Ni-57 at a beam energy of 90 MeV. The linear polarization was measured with a EUROBALL cluster detector and a prototype of an encapsulated six-fold segmented hexaconical Ge-detector. The spin of the 3701 keV level in Ni-57 was confirmed to be I = 9/2 and its parity determined to be positive.
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| 9. |
- Svensson, C. E., et al.
(author)
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Decay Out of the Doubly Magic Superdeformed Band in the N=Z Nucleus 60Zn
- 1999
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In: Physical Review Letters. - 1079-7114. ; 82:17, s. 3400-3403
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Journal article (peer-reviewed)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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| 10. |
- Ward, D., et al.
(author)
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Band Structure of 68Ge
- 2001
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In: Physical Review C (Nuclear Physics). - 0556-2813. ; 63:1
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Journal article (peer-reviewed)abstract
- The nucleus Ge-68 has been studied by gamma-ray spectroscopy following its population at high spin in the reaction Ca-40(S-32,4p) Ge-68. The reaction channel was selected with the Microball array and gamma rays were detected with the Gammasphere array. The level scheme is very complex, reflecting the many different, and presumably mixed, excitation modes in this nucleus. Nevertheless, there appear to be some simplifications in the spin range above 18 (h) over bar where we have identified a superdeformed band and several terminating bands. The results are compared with a cranked Nilsson-Strutinsky model without pairing.
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| 11. |
- Andreoiu, Corina, et al.
(author)
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Doorway States in the Gamma Decay-out of the Yrast Superdeformed Band in 59Cu
- 2003
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In: Physical Review Letters. - 1079-7114. ; 91:23
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Journal article (peer-reviewed)abstract
- The decay-out process of the yrast superdeformed band in Cu-59 has been investigated. The firm determination of spin, parity, excitation energy, and configuration of the states involved in this process constitutes a unique situation for a detailed understanding of the decay-out mechanism. A theoretical model is introduced that includes a residual interaction and tunneling matrix element between bands, calculated in the configuration-dependent cranked Nilsson-Strutinsky model. This interaction causes the decay to occur via a small number of observed doorway states.
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| 12. |
- Andreoiu, Corina, et al.
(author)
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Evolution of Shapes in 59Cu
- 2002
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In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 14:3, s. 317-348
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Journal article (peer-reviewed)abstract
- High-spin states in Cu-59 were populated using the fusion-evaporation reaction Si-28 + Ca-40 at a beam energy of 122 MeV. The Gammasphere Ge-detector array in conjunction with the 4pi charged-particle detector array Microball allowed for the detection of gamma-rays in coincidence with evaporated light particles. The resulting extensive high-spin decay scheme of Cu-59 is presented, which comprises more than 320 gamma-ray transitions connecting about 150 excited states. Their spins and parities have been assigned via directional correlations of gamma-rays emitted from oriented states. Average quadrupole moments of rotational bands have been determined from the analysis of residual Doppler shifts. Shell model calculations in the fp shell are invoked to study some of the low-spin states, while the experimental characteristics of the rotational bands are analyzed in the configuration-dependent cranked Nilsson-Strutinsky (CNS) approach.
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| 13. |
- Gadea, A., et al.
(author)
-
Spectroscopy at N=Z with EUROBALL III
- 1999
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In: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 495, s. 195-198
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Conference paper (peer-reviewed)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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| 14. |
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| 15. |
- Plettner, C., et al.
(author)
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Very high rotational frequencies and band termination in 73Br
- 2000
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In: Physical Review C - Nuclear Physics. - 0556-2813. ; 62:1, s. 143131-143136
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Journal article (peer-reviewed)abstract
- Rotational bands in 73Br have been investigated up to spins of I = 65/2 using the EUROBALL III spectrometer. One of the negative-parity bands displays the highest rotational frequency ℏω= 1.85 MeV reported to date in nuclei with A ≥ 25. At high frequencies, the experimental J(2) dynamic moment of inertia for all bands decreases to very low values, J(2) ≤ 10ℏ2 MeV-1. The bands are described in the configuration-dependent cranked Nilsson-Strutinsky model. The calculations indicate that one of the negative-parity bands is observed up to its terminating single-particle state at spin 63/2. This result establishes the first band termination in the A ≈ 70 mass region.
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| 16. |
- Rainovski, G, et al.
(author)
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Shape coexistence at high spin in the N = Z+2 nucleus Se-70
- 2002
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In: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899. ; 28:10, s. 2617-2625
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Journal article (peer-reviewed)abstract
- The nucleus Se-70 was studied using the Ca-40(Ca-40, 2alpha2p) reaction at a beam energy of 185 MeV. Gamma rays were measured with the EUROBALL III spectrometer. The known positive-parity bands have been extended and one new band of positive parity and two of negative parity have been identified. These bands are interpreted in terms of the cranked Nilsson-Strutinsky approach. Calculations suggest that the two negative-parity bands, which have the same signature, are both based on a configuration with two protons and three neutrons lifted from the fp shell to the g(9/2) orbital, but at different nuclear shapes. This represents a shape coexistence at high spin.
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| 17. |
- Recchia, F, et al.
(author)
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Position resolution of the prototype AGATA triple-cluster detector from an in-beam experiment
- 2009
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 604:3, s. 555-562
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Journal article (peer-reviewed)abstract
- AGATA belongs to a new generation of gamma-ray detector arrays for nuclear spectroscopy at present in its final stage of development. The detectors of these new arrays will be based on 36-fold electronically segmented coaxial germanium diodes operated in position sensitive mode. An in-beam test of the AGATA prototype triple cluster detector was carried out with the purpose of demonstrating the feasibility of such detectors and in order to measure the most sensitive parameters for their overall performance. An inverse kinematics reaction was performed, using a Ti-48 beam at an energy of 100MeV, impinging on a deuterated titanium tat-get. The results from the analysis of the experimental data, compared with the predictions of Monte Carlo Simulations, give an estimation of the position sensitivity of these detectors of about 5 mm FWHM, consistent with the specifications required. (C) 2009 Elsevier B.V. All rights reserved.
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| 18. |
- Rudolph, Dirk, et al.
(author)
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Gamma-decay Lifetime Measurements in the Second Minimum of 58Cu
- 2001
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In: Physical Review C (Nuclear Physics). - 0556-2813. ; 63:2
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Journal article (peer-reviewed)abstract
- The individual lifetimes of three low-lying states in the proton-decaying well-deformed rotational band in the second minimum of the N = Z nucleus Cu-58 were determined. Doppler-shift attenuated gamma -ray lineshapes were analyzed following the fusion-evaporation reaction C-40,(Mg-24,1 alpha 1p1n)Cu-58 and using the EUROBALL gamma -ray spectrometer coupled to ancillary detector systems. The deduced transitional quadrupole moments confirm the predicted increase of deformation towards the bottom of the band. The gamma decay-out strength hints towards a nonstatistical pattern.
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| 19. |
- Rudolph, Dirk, et al.
(author)
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The Lifetime of the Proton-decaying 8915 keV State in 58Cu
- 2001
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In: Nuclear Physics, Section A. - 0375-9474. ; 694, s. 132-146
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Journal article (peer-reviewed)abstract
- Energy correlations between gamma -ray transitions and the prompt proton decay line in Cu-58 were studied by means of the fusion-evaporation reaction Ca-40(Mg-24,1 alpha 1p1n) using the EUROBALL spectrometer coupled to ancillary detector devices. A lifetime of 0.06 < tau < 0.58 ps for the 8915 keV proton-decaying state in Cu-58 is deduced. (C) 2001 Elsevier Science B.V. All rights reserved.
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| 20. |
- Stefanescu, I, et al.
(author)
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High-spin states and band terminations in As-69
- 2004
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 70:4
-
Journal article (peer-reviewed)abstract
- Excited levels in As-69 were studied using the Ca-40(S-32,3p)As-69 reaction at 95 and 105 MeV beam energy. Gamma rays were detected with the EUROBALL spectrometer operated in conjunction with the Neutron Wall and the charged-particle detector array EUCLIDES. New level sequences with positive and negative parity were identified from 3p-gammagamma and gammagammagamma coincidences. Spins were assigned to many of the levels on the basis of directional correlations of oriented states measurements. The previously observed positive-parity band was extended to spin 45/2(+) and it was found to exhibit a crossing with another configuration identified up to spin 53/2(+). Three negative-parity bands were observed for the first time up to spins (43/2(-)), 39/2(-), and (41/2(-)). The previously known band was extended to spin (49/2(-)). No evidence for superdeformation was found, despite very high counting statistics. Configurations were assigned to each of the observed bands through comparisons to the cranked Nilsson-Strutinsky calculations.
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| 21. |
- Stefanova, E. A., et al.
(author)
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Four-quasiparticle alignments in Ge-66
- 2003
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In: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 34:4, s. 2237-2240
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Journal article (peer-reviewed)abstract
- Above angular momentum 10(+), we found two positive-parity sequences, connected by energetically staggered DeltaI = 1 M1 transitions. The total Routhian surface calculations predict a strong triaxial deformation for them. To our knowledge, this is the first observation of staggered M1 transitions in a deformed four-quasiparticle pi(g(9/2)(2))v(g(9/2)(2)) regime.
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| 22. |
- Stefanova, E. A., et al.
(author)
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Four-quasiparticle alignments in Ge-66
- 2003
-
In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 67:5
-
Journal article (peer-reviewed)abstract
- The neutron-deficient nucleus Ge-66 was populated at high spin in two experiments using the reaction Ca-40(S-32,alpha2p) at beam energies of 105 and 95 MeV. In the first experiment, a self-supporting Ca-40 target was used, while a gold-backed target of similar thickness was used in the second experiment. gamma rays were detected with the EUROBALL array, combined with the charged-particle detector array EUCLIDES and the Neutron Wall. The level scheme of Ge-66 was extended up to Eapproximate to18 MeV and I-pi=(23(-)). Above angular momentum 10(+), we found two sequences, connected by energetically staggered DeltaI=1 M1 transitions. The total Routhian surface calculations describe Ge-66 at lower spins as a gamma-soft nucleus having a moderate deformation of beta(2)approximate to0.23, while a triaxial deformation is predicted for the band structures above I-pi=10(+). To our knowledge, this is the first observation of staggered M1 transitions in a deformed four-quasiparticle pi(g(9/2)(2))nu(g(9/2)(2)) structure.
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| 23. |
- Valiente-Dobon, JJ, et al.
(author)
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Evidence for nontermination of rotational bands in Kr-74
- 2005
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In: Physical Review Letters. - 1079-7114. ; 95:23
-
Journal article (peer-reviewed)abstract
- Three rotational bands in Kr-74 were studied up to (in one case one transition short of) the maximum spin I-max of their respective single-particle configurations. Their lifetimes have been determined using the Doppler-shift attenuation method. The deduced transition quadrupole moments reveal a modest decrease, but far from a complete loss of collectivity at the maximum spin I-max. This feature, together with the results of mean field calculations, indicates that the observed bands do not terminate at I=I-max.
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