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Title: Studies of the shapes of heavy pear-shaped nuclei at ISOLDE

Abstract

For certain combinations of protons and neutrons there is a theoretical expectation that the shape of nuclei can assume octupole deformation, which would give rise to reflection asymmetry or a ”pear-shape” in the intrinsic frame, either dynamically (octupole vibrations) or statically (permanent octupole deformation). I will briefly review the historic evidence for reflection asymmetry in nuclei and describe how recent experiments carried out at REX-ISOLDE have constrained nuclear theory and how they contribute to tests of extensions of the Standard Model. I will also discuss future prospects for measuring nuclear shapes from Coulomb Excitation: experiments are being planned that will exploit beams from HIE-ISOLDE that are cooled in the TSR storage ring and injected into a solenoidal spectrometer similar to the HELIOS device developed at the Argonne National Laboratory.

Authors:
 [1]
  1. Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE (United Kingdom)
Publication Date:
OSTI Identifier:
22608491
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1753; Journal Issue: 1; Conference: Latin American symposium on nuclear physics and applications, Medellin (Colombia), 30 Nov - 4 Dec 2015; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ANL; ASYMMETRY; BEAMS; COULOMB EXCITATION; DEFORMATION; HELIOS DEVICES; NEUTRONS; NUCLEAR THEORY; NUCLEI; OCTUPOLES; PEARS; PROTONS; REFLECTION; REVIEWS; SPECTROMETERS; STANDARD MODEL; TSR STORAGE RING

Citation Formats

Butler, P. A., E-mail: peter.butler@liverpool.ac.uk. Studies of the shapes of heavy pear-shaped nuclei at ISOLDE. United States: N. p., 2016. Web. doi:10.1063/1.4955343.
Butler, P. A., E-mail: peter.butler@liverpool.ac.uk. Studies of the shapes of heavy pear-shaped nuclei at ISOLDE. United States. doi:10.1063/1.4955343.
Butler, P. A., E-mail: peter.butler@liverpool.ac.uk. 2016. "Studies of the shapes of heavy pear-shaped nuclei at ISOLDE". United States. doi:10.1063/1.4955343.
@article{osti_22608491,
title = {Studies of the shapes of heavy pear-shaped nuclei at ISOLDE},
author = {Butler, P. A., E-mail: peter.butler@liverpool.ac.uk},
abstractNote = {For certain combinations of protons and neutrons there is a theoretical expectation that the shape of nuclei can assume octupole deformation, which would give rise to reflection asymmetry or a ”pear-shape” in the intrinsic frame, either dynamically (octupole vibrations) or statically (permanent octupole deformation). I will briefly review the historic evidence for reflection asymmetry in nuclei and describe how recent experiments carried out at REX-ISOLDE have constrained nuclear theory and how they contribute to tests of extensions of the Standard Model. I will also discuss future prospects for measuring nuclear shapes from Coulomb Excitation: experiments are being planned that will exploit beams from HIE-ISOLDE that are cooled in the TSR storage ring and injected into a solenoidal spectrometer similar to the HELIOS device developed at the Argonne National Laboratory.},
doi = {10.1063/1.4955343},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1753,
place = {United States},
year = 2016,
month = 7
}
  • The coherent state model is extended to negative parity states. Thus three positive (ground, beta, and gamma) and three negative parity bands are projected out from three orthogonal states exhibiting both quadrupole and octupole deformations. An effective Hamiltonian acting on the space of projected states is constructed. For illustration, the numerical application is confined to the ground and K{sup {pi}}=0{sup {minus}} bands. In a certain range of deformations these bands show a {open_quotes}shell{close_quotes} structure. Good agreement with experimental data in {sup 218,220,226}Ra is obtained for energy levels and E1 transition probabilities. Specific features like the interleaved structure, the low energymore » of the state 1{sup {minus}}, and strong E1 transitions are well described. {copyright} {ital 1997} {ital The American Physical Society}« less
  • The shape evolutions of the pear-shaped nucleimore » $$^{224}$$Ra and even-even $$^{144-154}$$Ba with temperature are investigated by the finite-temperature relativistic mean field theory with the treatment of pairing correlations by the BCS approach. We study the free energy surfaces as well as the bulk properties including deformations, pairing gaps, excitation energy, and specific heat for the global minimum. For $$^{224}$$Ra, three discontinuities found in the specific heat curve indicate the pairing transition at temperature 0.4 MeV, and two shape transitions at temperatures 0.9 and 1.0 MeV, namely one from quadrupole-octupole deformed to quadrupole deformed, and the other from quadrupole deformed to spherical. Furthermore, the gaps at $N$=136 and $Z$=88 are responsible for stabilizing the octupole-deformed global minimum at low temperatures. Similar pairing transition at $$T\sim$$0.5 MeV and shape transitions at $T$=0.5-2.2 MeV are found for even-even $$^{144-154}$$Ba. Finally, the transition temperatures are roughly proportional to the corresponding deformations at the ground states.« less