| 1. |
- Lerma, F., et al.
(författare)
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Superdeformed bands in Sr80-83, Y82-84, Zr-83,Zr-84 : Transition quadrupole moments, moments of inertia, and configuration assignments
- 2003
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 67:4, s. 044310-
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Tidskriftsartikel (refereegranskat)abstract
- Multiple superdeformed bands in the nuclei Sr80-83, Y82-84, and Zr-83,Zr-84 have been studied in a backed-target experiment, using the Gammasphere and the Microball 4pi detector arrays. For 15 bands in these nuclei, average transition quadrupole moments have been measured with high accuracy, using the Doppler-shift attenuation method. Among these are the newly observed superdeformed bands in Y-83,Y-84, which are isospectral with the bands in Sr-82,Sr-83. These isospectral bands have nearly identical transition quadrupole moments. Two of the bands in Sr-81 interact and cross transitions between them are observed. The present measurements place stringent conditions on configuration assignments for the bands obtained from two types of mean-field calculations, leading to a consistent understanding of the mass similar to80 superdeformed bands. The assignments for different bands arise from one or more nucleons occupying the N-0=5h(11/2) intruder orbital.
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| 2. |
- Satula, W., et al.
(författare)
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A number projected model with generalized pairing interaction
- 2000
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Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 676, s. 120-142
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Tidskriftsartikel (refereegranskat)abstract
- A mean-held model with a generalized pairing interaction that accounts for neutron-proton pairing is presented. Both the BCS as well as number-projected solutions of the model are presented. For the latter case the Lipkin-Nogami projection technique was extended to encompass the case of nonseparable proton-neutron systems. The influence of the projection on various pairing phases is discussed. In particular, it is shown that number-projection allows For mixing of different pairing phases but, simultanously, acts destructively on the proton-neutron correlations, The basic implications of proton-neutron pairing correlations on nuclear masses are discussed. It is shown that these correlations may provide a natural microscopic explanation of the Wigner energy lacking in mean-field models. A possible phase transition from isovector to isoscalar pairing condensate at high angular momenta is also discussed. In particular predictions for the dynamical moments of inertia for the superdeformed band in Ru-88 are given.
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| 3. |
- Satula, W., et al.
(författare)
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Cranking in isospace - Towards a consistent mean-field description of N = Z nuclei
- 2001
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Ingår i: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 32:9, s. 2441-2456
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Tidskriftsartikel (refereegranskat)abstract
- Excitation spectra DeltaE(T) of T = 0, 1, 2 states in even-even (e-e) and odd-odd (o-o) N = Z nuclei are analyzed within a mean-field based model involving isovector and isoscalar pairing interactions and the iso-cranking formalism applied to restore approximately isospin symmetry. It is shown that T = 0 states in o-o and T = 1 states in e-e nuclei correspond to two-quasiparticle, time-reversal symmetry breaking excitations since their angular momenta are I not equal 0. On the other hand the lowest T = 2 states in e-e and T = 1 states in o-o nuclei, which both are similar in structure to their even-even isobaric analogue states, are described as e-e type vacua excited (iso-cranked) in isospace. It appears that in all cases isoscalar pairing plays a crucial role in restoring the proper value of the inertia parameter in isospace i.e. DeltaE(T).
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| 4. |
- Satula, W., et al.
(författare)
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Microscopic structure of fundamental excitations in N = Z nuclei
- 2001
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 8705:5
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Tidskriftsartikel (refereegranskat)abstract
- An extended mean-field model is presented that describes states of different isospin in odd-odd and even-even nuclei. Excitation energies of the T = 1 states in even-even as well as T = 0 and T = 1 states in odd-odd N = Z nuclei are calculated. It is shown that the structure of these states can be determined in a consistent manner when both isoscalar and isovector pairing collectivity as well as isospin projection (treated here within the isocranking approximation) are taken into account. In particular, in odd-odd N = Z nuclei, the interplay between quasiparticle excitations (relevant for the case of T = 0 states) and isorotations (relevant for the case of T = 1 states) explains the near degeneracy of these states.
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| 5. |
- Satula, W., et al.
(författare)
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Rotations in isospace : A doorway to the understanding of neutron-proton superfluidity in N = Z nuclei
- 2001
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 86:20, s. 4488-4491
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Tidskriftsartikel (refereegranskat)abstract
- The T = 2 excitations in even-even N = Z nuclei are calculated within the isospin cranked mean-held approach. The response of pairing correlations to rotation in isospace is investigated. Whereas the isovector pairing rather modestly modifies the single-particle moment of inertia in isospace, the isoscalar pairing strongly reduces its value. This reduction of the isomoments of inertia with respect to its rigid body value is a strong indicator of collective isoscalar pairing correlations. These results are further generalized yielding beautiful analogies between the role of isovector pairing for the case of spatial rotations and the role of isoscalar pairing for the case of isorotations.
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| 6. |
- Wyss, Ramon A., et al.
(författare)
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Rotating N=Z nuclei - A probe to the t=0 and t=1 pairing correlations
- 2001
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Ingår i: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 32:9, s. 2457-2468
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Tidskriftsartikel (refereegranskat)abstract
- A study of heavy N=Z nuclei including t=1, t(z)=+/-1 pairing only clearly reveals the shortcoming of that model in T-z=0 nuclei. We present a simple model in which we study the response of isoscalar t=0 and isovector t=1 pairing correlations to rotational motion. In particular, we address the role played by the t=1 and t=0 pair gaps with respect to the band crossing frequency. We argue that the t=1 neutron-proton pair field is of limited importance in even-even nuclei. For the t=0 pair field, we introduce two different pairing modes. One is invariant with respect to signature symmetry and one is not. The signature conserving mode results in a delay of the band crossing frequency, whereas the signature breaking part enhances the rigidity of the moment of inertia.
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| 7. |
- Xu, F. R., et al.
(författare)
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Quadrupole pairing interaction and signature inversion
- 2000
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Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 669:02-jan, s. 119-134
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Tidskriftsartikel (refereegranskat)abstract
- The signature inversion in the pi h(11/2) x vh(11/2) rotational bands of the odd-odd Cs and La isotopes and the pi h(11/2) x vi(13/2) bands of the odd-odd Tb, Ho and Tm nuclei is investigated using pairing and deformation self-consistent mean-field calculations, The model can rather satisfactorily account for the anomalous signature splitting provided that spin assignments in some of the bands are revised. Our calculations show that signature inversion can appear already at axially symmetric shapes. It is found that this is due to the contribution of the (lambda mu) = (22) component of the quadrupole-pairing interaction to the mean-field potential.
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