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Title: Octupole collectivity in the Sm isotopes

Abstract

Microscopic models suggest the occurrence of strong octupole correlations in nuclei with N{approx_equal}88. To examine the signatures of octupole correlations in this region, the spdf interacting boson approximation model is applied to Sm isotopes with N=86-92. The effects of including multiple negative-parity bosons in this basis are compared with more standard one negative-parity boson calculations and are analyzed in terms of signatures for strong octupole correlations. It is found that multiple negative-parity bosons are needed to describe properties at medium spin. Bands with strong octupole correlations (multiple negative-parity bosons) become yrast at medium spin in {sup 148,150}Sm. This region shares some similarities with the light actinides, where strong octupole correlations were also found at medium spin.

Authors:
 [1];  [2];  [1];  [3];  [4];  [1];  [5]
  1. Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520-8124 (United States)
  2. (Germany)
  3. (Romania)
  4. Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520-8120 (United States)
  5. Institut fuer Kernphysik, Technische Universitaet Darmstadt, Schlossgartenstrasse 9, D-64289 Darmstadt (Germany)
Publication Date:
OSTI Identifier:
20771079
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 72; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevC.72.064302; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ACTINIDES; APPROXIMATIONS; CORRELATIONS; DEFORMED NUCLEI; INTERACTING BOSON MODEL; OCTUPOLES; PARITY; SAMARIUM 150; SPIN; YRAST STATES

Citation Formats

Babilon, M., Institut fuer Kernphysik, Technische Universitaet Darmstadt, Schlossgartenstrasse 9, D-64289 Darmstadt, Zamfir, N.V., National Institute for Physics and Nuclear Engineering, Bucharest-Magurele, Kusnezov, D., McCutchan, E.A., and Zilges, A. Octupole collectivity in the Sm isotopes. United States: N. p., 2005. Web. doi:10.1103/PhysRevC.72.064302.
Babilon, M., Institut fuer Kernphysik, Technische Universitaet Darmstadt, Schlossgartenstrasse 9, D-64289 Darmstadt, Zamfir, N.V., National Institute for Physics and Nuclear Engineering, Bucharest-Magurele, Kusnezov, D., McCutchan, E.A., & Zilges, A. Octupole collectivity in the Sm isotopes. United States. doi:10.1103/PhysRevC.72.064302.
Babilon, M., Institut fuer Kernphysik, Technische Universitaet Darmstadt, Schlossgartenstrasse 9, D-64289 Darmstadt, Zamfir, N.V., National Institute for Physics and Nuclear Engineering, Bucharest-Magurele, Kusnezov, D., McCutchan, E.A., and Zilges, A. Thu . "Octupole collectivity in the Sm isotopes". United States. doi:10.1103/PhysRevC.72.064302.
@article{osti_20771079,
title = {Octupole collectivity in the Sm isotopes},
author = {Babilon, M. and Institut fuer Kernphysik, Technische Universitaet Darmstadt, Schlossgartenstrasse 9, D-64289 Darmstadt and Zamfir, N.V. and National Institute for Physics and Nuclear Engineering, Bucharest-Magurele and Kusnezov, D. and McCutchan, E.A. and Zilges, A.},
abstractNote = {Microscopic models suggest the occurrence of strong octupole correlations in nuclei with N{approx_equal}88. To examine the signatures of octupole correlations in this region, the spdf interacting boson approximation model is applied to Sm isotopes with N=86-92. The effects of including multiple negative-parity bosons in this basis are compared with more standard one negative-parity boson calculations and are analyzed in terms of signatures for strong octupole correlations. It is found that multiple negative-parity bosons are needed to describe properties at medium spin. Bands with strong octupole correlations (multiple negative-parity bosons) become yrast at medium spin in {sup 148,150}Sm. This region shares some similarities with the light actinides, where strong octupole correlations were also found at medium spin.},
doi = {10.1103/PhysRevC.72.064302},
journal = {Physical Review. C, Nuclear Physics},
number = 6,
volume = 72,
place = {United States},
year = {Thu Dec 15 00:00:00 EST 2005},
month = {Thu Dec 15 00:00:00 EST 2005}
}
  • The negative parity energy levels of the even-even Ge isotopes with mass number between 64 and 76 are studied systematically by enlarging the model space of the interacting boson approximation model to include both collective and noncollective basis states. The basis states consist of [ital N][sub [ital B]][minus]1 s[ital d]-boson plus a [ital f]-boson configuration and [ital N][sub [ital B]][minus]1 [ital sd] boson plus a fermion pair configuration. The fermions are allowed to occupy the [ital f][sub 5/2] and [ital g][sub 9/2] single-particle orbitals, respectively. It was found that the negative parity energy levels of [sup 64[minus]76]Ge nuclei can bemore » described reasonably well. The intensities of the collective configuration in 3[sup [minus]] states increase when going from nucleus [sup 64]Ge to nucleus [sup 72]Ge and decrease from nucleus [sup 72]Ge to nucleus [sup 74]Ge. The [ital B]([ital E]3;3[sub 1][sup [minus]][r arrow]0[sub 1][sup +]) values are calculated and compared with the available observed data.« less
  • A half-life of {ital T}{sub 1/2}=50(7) ps was measured for the 3{sub 1}{sup {minus}} level in {sup 96}Zr. The deduced {ital B}({ital E}3) rate of 65(10) W.u. makes this 3{sub 1}{sup {minus}}{r arrow}0{sub 1}{sup +} transition the fastest known. The results interpreted in terms of the random phase approximation and a deformed shell model suggest octupole instability around {sup 96}Zr.
  • The nucleus {sup 144}Sm has been studied with the ({ital n},{ital n}{prime}{gamma}) reaction and lifetimes of many states have been extracted from the observed Doppler shifts of the deexciting {gamma} rays. A large number of fast {ital E}1 transitions have been observed and have led to the identification of possible members of the octupole-octupole and the quadrupole-octupole multiplets. Substantial fragmentation of the two-phonon octupole strength is indicated.
  • [ital E]3 matrix elements have been determined for transitions between states up to [ital I][sup [pi]]=13[sup [minus]] in [sup 148]Nd, providing direct evidence for strong octupole collectivity in a rotational band. These values, as well as the corresponding [ital E]1 and [ital E]2 matrix elements, were obtained from Coulomb excitation data using [sup 58]Ni and [sup 92]Mo ions, projectile excitation using a [sup 208]Pb target, and from recoil distance lifetime measurements. The results are consistent with collective model predictions for [sup 148]Nd assuming intrinsic quadrupole and octupole moments of [ital Q][sub 20][approx]400 [ital e] fm[sup 2] and [ital Q][sub 30][approx]1500more » [ital e] fm[sup 3]. The [ital E]3 strength coupling the negative-parity states to the [beta] band is found to be appreciable.« less
  • The angular momenta and parities of the low-lying states of [sup 132]Sn have been firmly determined through studies of the [beta] decay of [sup 132]In. The lowest lying state with a negtive parity is shown to have a collective octupole character. Several particle-hole multiplets have been identified, including the lowest lying proton excitation. More than about 20% of the theoretically estimated bound states of [sup 132]Sn have been identified.