| 1. |
- Cederwall, Bo, et al.
(author)
-
Evidence for a spin-aligned neutron-proton paired phase from the level structure of 92Pd
- 2011
-
In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 469:7328, s. 68-71
-
Journal article (peer-reviewed)abstract
- Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work(1) that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing(2-6), in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus Pd-92. Gamma rays emitted following the Ni-58(Ar-36,2n)Pd-92 fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution c-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction(2-6). We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling(7,8)) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.
|
|
| 2. |
- Andgren, Karin, et al.
(author)
-
Low-spin collective behavior in the transitional nuclei Mo-86,Mo-88
- 2007
-
In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 76:1, s. 014307-
-
Journal article (peer-reviewed)abstract
- Low-spin structures in Mo-86,Mo-88 were populated using the Ni-58(Ar-36, x alpha yp) heavy-ion fusion-evaporation reaction at a beam energy of 111 MeV. Charged particles and gamma rays were emitted in the reactions and detected by the DIAMANT CsI ball and the EXOGAM Ge array, respectively. In addition to the previously reported low-to-medium spin states in these nuclei, new low-spin structures were observed. Angular correlation and linear polarization measurements were performed in order to unambiguously determine the spins and parities of intensely populated states in Mo-88. Quasiparticle Random Phase Approximation (QRPA) calculations were performed for the first and second excited 2(+) states in Mo-86 and Mo-88. The results are in qualitative agreement with the experimental results, supporting a collective interpretation of the low-spin states for these transitional nuclei.
|
|
| 3. |
- Palacz, M., et al.
(author)
-
Investigations of Neutron Deficient Nuclei Close to 100Sn with EUROBALL
- 2001
-
In: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254 .- 1509-5770. ; 32, s. 999-1003
-
Journal article (peer-reviewed)abstract
- Excited states of nuclei in the vicinity of Sn-100 have been studied using: the EUROBALL detector array. Gamma-ray lines from Sn-103 have been identified for the first time, and a level scheme of low-lying excited states of Sn-103 has been established. New constraints on energies of single particle orbitals with respect to the Sn-100 core are obtained.
|
|
| 4. |
- Fahlander, Claes, et al.
(author)
-
Excited States in 103Sn: Neutron Single-particle Energies with Respect to 100Sn
- 2001
-
In: Physical Review C (Nuclear Physics). - 0556-2813 .- 1089-490X. ; 63:2
-
Journal article (peer-reviewed)abstract
- Gamma-ray lines from Sn-103 have been identified for the first time using EUROBALL and ancillary detectors. The level scheme of Sn-103 has been established by means of particle-gated gamma gamma coincidences. The energy spacing between the g(7/2) and d(5/2) neutron single-particle orbitals is determined from the excited states in Sn-103.
|
|
| 5. |
- Sohler, D, et al.
(author)
-
Neutron Excitations Across the N=50 Shell Gap in 102In
- 2002
-
In: Nuclear Physics, Section A. - : Elsevier. - 0375-9474 .- 1873-1554. ; 708:3-4, s. 181-189
-
Journal article (peer-reviewed)abstract
- The structure of In-102 has been investigated by in-beam gamma-spectroscopic methods. Knowledge on the excited states of this nucleus has significantly been extended. Three cascades of transitions were observed to exceed the spin-energy domain spanned by the pig(9/2)(-1)v(d(5/2),g(7/2))(3) configurations. The new high spin states at similar to 4 MeV excitation energy could be assigned to the pig(9/2)(-1)v(d(5/2), g(7/2))(2)h (11/2) configuration, while at least those at 4.733, 5.192 and 5.853 MeV most likely arise from the vg(9/2) --> vd(5/2), g(7/2) one-particle-one-hole excitation across the N = 50 shell closure.
|
|
| 6. |
- Sohler, D, et al.
(author)
-
Maximally Aligned States in the Proton Drip Line Nucleus 106Sb
- 2005
-
In: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 753:3-4, s. 251-262
-
Journal article (peer-reviewed)abstract
- High-spin states in Sb-106 have been investigated in the Fe-54(Ni-58, 1α 1p1n) reaction by in-beam γ-spectroscopic methods using the EUROBALL detector array equipped with charged particle and neutron detectors. On the basis of measured γγ-coincidence relations, angular distributions, and linear polarization ratios a significantly extended level scheme has been constructed up to spin and parity I-π = (19(-)) and E-x ∼ 6.5 MeV. The experimental results are interpreted within the framework of the gdsh shell model using a realistic effective nucleon-nucleon interaction. Candidates for states with fully aligned angular momenta in the π(d(5/2), g(7/2))(1) v (d(5/2), g(7/2))(5) valence space are identified at 4338 and 5203 keV, as well as in the π(d(5/2), g(7/2))(1) V(d(5/2), g(7/2))(4)h(11/2)(1) space at 6087, 6573 and 6783 keV.
|
|
| 7. |
- Bäck, Torbjörn, et al.
(author)
-
First observation of gamma-rays from the proton emitter Au-171
- 2003
-
In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 16:4, s. 489-494
-
Journal article (peer-reviewed)abstract
- Gamma-rays from the alpha- and proton-unstable nuclide Au-171 have been observed for the first time. The gamma-rays were correlated with both a proton- and an alpha-particle decay branch, confirming that the nucleus decays by alpha and proton emission from a single (11/2(-)) state. The measurement confirms the previously determined half-lives for these particle decays but the present values are of higher precision. In addition, a longer half-life than determined in previous work was measured for the proton-unstable tentative ground state. The results are discussed in relation to structures in neighbouring nuclei and compared with a Strutinsky-type TRS calculation.
|
|
| 8. |
- Bäck, Torbjörn, et al.
(author)
-
Spectroscopy of the neutron-deficient nuclide Pt-171
- 2003
-
In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 17:1, s. 1-5
-
Journal article (peer-reviewed)abstract
- A number of previously unobserved gamma-rays emitted from the neutron-deficient nuclide Pt-171 have been identified using the recoil decay tagging technique. The level scheme has been updated using information from gamma-gamma coincidences and angular distribution measurements. To further confirm the assignments of the gamma-rays to Pt-171, the events were correlated with the alpha-decay of the daughter nucleus Os-167.
|
|
| 9. |
- Ideguchi, E., et al.
(author)
-
High-spin intruder band in In-107
- 2010
-
In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 81:3, s. 034303-
-
Journal article (peer-reviewed)abstract
- High-spin states in the neutron-deficient nucleus In-107 were studied via the Ni-58(Cr-52,3p) reaction. In-beam gamma rays were measured using the JUROGAM detector array. A rotational cascade consisting of ten gamma-ray transitions, which decays to the 19/2(+) level at 2.002 MeV, was observed. The band exhibits the features typical for smooth terminating bands that also appear in rotational bands of heavier nuclei in the A similar to 100 region. The results are compared with total Routhian surface and cranked Nilsson-Strutinsky calculations.
|
|
| 10. |
- Ideguchi, Eiji, et al.
(author)
-
Superdeformation in 91Tc
- 2000
-
In: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 492:3-4, s. 245-253
-
Journal article (peer-reviewed)abstract
- A high-spin rotational band with 11 gamma -ray transitions has barn observed in Tc-91. The dynamical moment of inertia as well as the transition quadrupole moment of 8.1(-1.4)(+1.9) eb measured for this band show the characteristics of a superdeformed band. However, the shape is more elongated than in the neighbouring A = 80-90 superdeformed nuclei. Theoretical interpretations of the band within the cranked Strutinsky approach based on two different Woods-Saxon potential parameterisations are presented. Even though an unambiguous configuration assignment proved difficult, both calculations indicate a larger deformation and at least three additional high-N intruder orbitals occupied compared to the lighter SD nuclei. (C) 2000 Elsevier Science B.V. All rights reserved.
|
|
