| 1. |
- Simpson, J., et al.
(author)
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Evolution of structure and shapes in Er 158 to ultrahigh spin
- 2023
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In: Physical Review C. - 2469-9985. ; 107:5
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Journal article (peer-reviewed)abstract
- The level structure of Er158 has been studied using the Gammasphere spectrometer via the Cd114(Ca48,4n) reaction at 215 MeV with both thin (self-supporting) and thick (backed) targets. The level scheme has been considerably extended with more than 200 new transitions and six new rotational structures, including two strongly coupled high-K bands. Configuration assignments for the new structures are based on their observed alignments, B(M1)/B(E2) ratios of reduced transition probabilities, excitation energies, and comparisons with neighboring nuclei and theoretical calculations. With increasing angular momentum, this nucleus exhibits Coriolis-induced alignments of both neutrons and protons before it then undergoes a rotation-induced transition from near-prolate collective rotation to a noncollective oblate configuration. This transition occurs via the mechanism of band termination around spin 45ħ in three rotational structures. Two distinct lifetime branches, consistent with the crossing of a collective "fast"rotational structure by an energetically favored "slow"terminating sequence, are confirmed for the positive-parity states, and similar behavior is established in the negative-parity states. Weak-intensity, high-energy transitions are observed to feed into the terminating states. At the highest spins, three collective bands with high dynamic moments of inertia and large quadrupole moments were identified. These bands are interpreted as triaxial strongly deformed structures and mark a return to collectivity at ultrahigh spin.
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| 2. |
- 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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| 3. |
- Cardona, R., et al.
(author)
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High-spin structure of normal-deformed bands in 84Zr
- 2003
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In: Physical Review C - Nuclear Physics. - 0556-2813. ; 68, s. 1-024303
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Journal article (peer-reviewed)abstract
- The reaction 58Ni(32S, α2p) at E lab= 135 MeV was used to populate high-spin states in 84Zr. The complete GAMMASPHERE and MICROBALL arrays were used to obtain clean γ- γ- γ line shapes to be analyzed by the Doppler shift attenuation method and to determine 27 lifetimes in the ground-state band and in two excited bands. Side-feeding times were also measured by comparing the line shapes gated with transitions above and below the state under study. The deduced electric quadrupole moments for the ground-state band are consistent with a very slow reduction with frequency with values ranging between 2.4(3) and 2.0(1)e b. The negative-parity bands feature also an approximate constancy of quadrupole moment with values similar to those in the ground-state band. Cranking calculations agree with this behavior in both parity bands and suggest an interpretation of the upper states in the ground-state band as part of a very slowly terminating band. Shell-dependent cranked Nilsson calculations explain a fourth γ cascade as pertaining to a noncollective structure terminating at I = 20+.
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| 4. |
- Devlin, M., et al.
(author)
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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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In: Physical Review Letters. - 1079-7114. ; 82, s. 5217-5220
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Journal article (peer-reviewed)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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| 5. |
- Döring, J., et al.
(author)
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Band terminations in the valence space of 86Zr
- 2000
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In: Physical Review C - Nuclear Physics. - 0556-2813. ; 61:3, s. 343101-343106
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Journal article (peer-reviewed)abstract
- High-spin states in 86Zr up to 30+ and 27- were observed via the 58Ni(32S,4p) reaction at 135 MeV beam energy using the combined GAMMASPHERE and MICROBALL systems. Calculations performed with the configuration-dependent shell-correction approach show that these states are built from six g9/2 neutrons and at most four protons excited from the p1/2,p3/2,f5/2 subshells to the g9/2 subshell at small deformation. The highest observed states at 27- and 30+ are interpreted as band-terminating states with the latter having the highest spin available in the valence space for 86Zr.
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| 6. |
- Gale, S. J., et al.
(author)
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Band termination spectroscopy in 157Er
- 1995
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In: Journal of Physics G: Nuclear and Particle Physics. - 0954-3899. ; 21:2, s. 193-213
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Journal article (peer-reviewed)abstract
- The level scheme of 157Er has been extended from a spin region where the nucleus behaves as a prolate rotor to a region where the spin is produced by the alignment of all or most of the available valence nucleons along the symmetry axis of a weakly deformed oblate shape. The level scheme was established at high spin using up to four-fold gamma -ray coincidences detected in the Eurogam spectrometer following the reaction 114Cd( 48Ca,5n)157Er at a bombarding energy of 210 MeV. Particularly favoured states have been established at IK=69/2+, 81/2+, 71/2+, 77/2-, 87-/2 and 89-/2. Specific single-particle configurations are assigned to these special states by comparison with cranked Nilsson-Strutinsky calculations. These states are related to structures observed in the neighbouring nuclei 158Er and 157Ho. These data provide the spectrum of single-particle states for the lowest lying valence orbitals above the 146Gd closed core.
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| 7. |
- Hagen, T. W., et al.
(author)
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Evolution of nuclear shapes in odd-mass yttrium and niobium isotopes from lifetime measurements following fission reactions
- 2017
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In: Physical Review C: covering nuclear physics. - 2469-9985. ; 95:3
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Journal article (peer-reviewed)abstract
- Lifetimes of excited states in Y99,Y101,Nb101,Nb103, and Nb105 were measured in an experiment using the recoil distance Doppler shift method at GANIL (Grand Accélérateur National d'Ions Lourds). The neutron-rich nuclei were produced in fission reactions between a U238 beam and a Be9 target. Prompt γ rays were measured with the EXOGAM array and correlated with fission fragments that were identified in mass and atomic number with the VAMOS++ spectrometer. The measured lifetimes, together with branching ratios, provide B(M1) and B(E2) values for the strongly coupled rotational bands built on the [422]5/2+ ground state in the Y and Nb nuclei with neutron number N≥60. The comparison of the experimental results with triaxial particle-rotor calculations provides information about the evolution of the nuclear shape in this mass region.
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| 8. |
- LaFosse, D. R., et al.
(author)
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Collective structures and band termination in 107Sb
- 2000
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In: Physical Review C - Nuclear Physics. - 0556-2813. ; 62:1
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Journal article (peer-reviewed)abstract
- High-spin states in the near proton-dripline nucleus 107Sb have been identified, and collectivity in this nucleus has been observed for the first time in the form of two rotational bands. One of the observed rotational structures is a ΔI = 1 band, and is interpreted as based on a π(g9/2)-1 ⊗ π(g7/2d5/2)2 proton configuration. A second structure has ΔI = 2 character, and is explained as being based on a πh11/2⊗[π(g9/2)-2 ⊗ π(g7/2d5/2)2] proton configuration through comparison with cranked Nilsson-Strutinsky model calculations. The calculations predict that this band terminates at a spin of 79/2 (Latin small letter h with stroke).
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| 9. |
- Lane, G. J., et al.
(author)
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Identification of excited states in doubly odd [Formula Presented]Sb : Smooth band termination
- 1997
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In: Physical Review C - Nuclear Physics. - 0556-2813. ; 55:5, s. 2127-2131
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Journal article (peer-reviewed)abstract
- Excited states in [Formula Presented]Sb have been identified for the first time in a series of [Formula Presented]-spectroscopy experiments using both thin and backed targets, including neutron-fold and recoil-mass measurements to provide unambiguous channel identification. The three decoupled intruder bands observed in [Formula Presented]Sb are based upon configurations involving 2p-2h excitations across the [Formula Presented] shell gap and show the features of smooth band termination. The yrast intruder band, which has been connected to the low-spin levels, is tentatively identified up to its predicted termination at [Formula Presented]. Excellent agreement with configuration-dependent cranked Nilsson-Strutinsky calculations is obtained for the high-spin states near termination.
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| 10. |
- Lieder, E. O., et al.
(author)
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DSAM Lifetime Studies for Gd-Nd nuclei with EUROBALL and AFRODITE
- 2008
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In: Frontiers in Nuclear Structure, Astrophysics, and Reactions, FINUSTAR 2007. - : AIP. - 1551-7616 .- 0094-243X. - 9780735405325 ; 1012, s. 383-385
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Conference paper (peer-reviewed)abstract
- Lifetimes of high-spin states have been measured for 142Gd and 134Nd with EU-ROBALL IV and AFRODITE, respectively, using DSAM. From calculations in the cranked Nilsson-Strutinsky model it was concluded that at the high-spin states of the (+,0)1 band, 142Gd represents a triaxial nucleus rotating around the longest principal axis.
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