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Title: Microscopic structure of deformed and superdeformed collective bands in rotating nuclei

Abstract

We investigate in self-consistent cranked Nilsson plus quasiparticle random-phase approximation the structure of {sup 190,192,194}Hg in their evolution from normal to superdeformation and from low to high rotational frequencies. The analysis of the energy levels suggests a splitting of few normally deformed bands into two or more branches. The investigation of the dynamical moments of inertia supports the octupole character of the low-lying negative parity superdeformed bands, in agreement with previous theoretical predictions and experimental findings. As a more direct confirm of their octupole nature, we obtain strong E1 transitions linking those bands to the yrast superdeformed band, in agreement with experiments. A similar result is shown to hold also for {sup 152}Dy. Like in {sup 152}Dy, the collectivity of the low-lying scissors mode gets enhanced with the onset of superdeformation.

Authors:
;  [1]; ; ;  [2]
  1. Institute of Particle and Nuclear Physics, Charles University, V. Holesovickach 2, CZ-18000 Prague 8 (Czech Republic)
  2. Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II' and Istituto Nazionale di Fisica Nucleare, Monte S. Angelo, Via Cintia I-80126 Naples (Italy)
Publication Date:
OSTI Identifier:
20995119
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevC.75.034306; (c) 2007 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; CRANKING MODEL; DYSPROSIUM 152; E1-TRANSITIONS; MASS NUMBER; MERCURY 194; MOMENT OF INERTIA; OCTUPOLES; PARITY; RANDOM PHASE APPROXIMATION; ROTATIONAL STATES; SHELL MODELS; SUPERDEFORMED NUCLEI; YRAST STATES

Citation Formats

Kvasil, J., Knapp, F., Lo Iudice, N., Andreozzi, F., and Porrino, A. Microscopic structure of deformed and superdeformed collective bands in rotating nuclei. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.034306.
Kvasil, J., Knapp, F., Lo Iudice, N., Andreozzi, F., & Porrino, A. Microscopic structure of deformed and superdeformed collective bands in rotating nuclei. United States. doi:10.1103/PHYSREVC.75.034306.
Kvasil, J., Knapp, F., Lo Iudice, N., Andreozzi, F., and Porrino, A. Thu . "Microscopic structure of deformed and superdeformed collective bands in rotating nuclei". United States. doi:10.1103/PHYSREVC.75.034306.
@article{osti_20995119,
title = {Microscopic structure of deformed and superdeformed collective bands in rotating nuclei},
author = {Kvasil, J. and Knapp, F. and Lo Iudice, N. and Andreozzi, F. and Porrino, A.},
abstractNote = {We investigate in self-consistent cranked Nilsson plus quasiparticle random-phase approximation the structure of {sup 190,192,194}Hg in their evolution from normal to superdeformation and from low to high rotational frequencies. The analysis of the energy levels suggests a splitting of few normally deformed bands into two or more branches. The investigation of the dynamical moments of inertia supports the octupole character of the low-lying negative parity superdeformed bands, in agreement with previous theoretical predictions and experimental findings. As a more direct confirm of their octupole nature, we obtain strong E1 transitions linking those bands to the yrast superdeformed band, in agreement with experiments. A similar result is shown to hold also for {sup 152}Dy. Like in {sup 152}Dy, the collectivity of the low-lying scissors mode gets enhanced with the onset of superdeformation.},
doi = {10.1103/PHYSREVC.75.034306},
journal = {Physical Review. C, Nuclear Physics},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • A shell-model theory, called the pseudo SU(3) model, which was proposed previously for giving the structure of low-lying states in heavy deformed nuclei is used to predict the number of 1/sup +/ states with strong M1 transitions to ground states for the nuclei /sup 154/Sm, /sup 156//sup --//sup 160/Gd, /sup 164/Dy, /sup 168/Er, /sup 174/Yb of the rare earth region and the actinide species /sup 232/Th, /sup 234//sup --//sup 240/U, /sup 242/Pu. Results are also given for E2 and M3 transition strengths in these nuclei. The measures provide a rigorous test of the theory, which in reality is a many-particlemore » Nilsson scheme, because the real M1, E2, and M3 operators are used in the calculations. It is found that the results for E2 strengths using the real quadrupole operator Q-script differ by less than 5 from those of calculations that use the operator Q-italic-tilde which is a generator of the pseudo SU(3) symmetry. This is so even for weak interband transitions. To further test the theory additional experimental information on the 2/sup +//sub ..gamma../ states is necessary. In particular, the 1/sup +/ ..-->.. 2/sup +//sub ..gamma../ decay strengths are needed to differentiate between theories for the structure of the giant M1 states. copyright 1987 Academic Press, Inc.« less
  • Microscopic analysis of the quantum (shell) effects related to the presence of the hexadecapole ({ital Y}{sub 4{mu}}; {mu}=0,2,4) components in the nuclear mean field is performed for the superdeformed nuclei in the mass {ital A} {similar_to} 150 region using the deformed Woods-Saxon potential. No shell effects favoring the {ital C}{sub 4}-symmetry are found. The calculations indicate, however, the existence of the {alpha}{sub 44}-deformation driving orbitals whose occupation might induce an {alpha}{sub 44}-polarization effect. For {sup 149}Gd and {sup 153}Dy nuclei, in which the existence of the {ital C}{sub 4}-symmetry effects is suspected, properties of several excited particle-hole configuration are analyzed.
  • The status of microscopic models for describing collective excitations in strongly deformed nuclei will be reviewed. The symplectic shell-model for light nuclei and its pseudo-symplectic extension for heavy systems will be presented as the most complete- and therefore the most challenging- of these theories. Because nucleons are treated as fermions and not bosons in the theory, consequences of the Pauli Exclusion Principle can be explored: all four rotational symmetry types are realized, not just the symmetric geometry used in collective model approaches; {beta}-excitations are non-leading SU(3) representations while {gamma}-vibrations correspond to K=2 rotor configurations; and energy surface minima are amore » result of competition between increases in binding and shell-gap energies when multi-{h_bar}{omega} configurations are taken into account, and not through high-order terms in the potential. The theory can be used to explore a variety of phenomena ranging from excitation energies and electromagnetic transition strengths of ordinary spectroscopy to questions that probe deeper into the internal dynamics of the many-body system as revealed, for example, through current flows measured in electron scattering experiments. The theory can even be used to determine the zero-neutrino, double-beta decay probabilities in strongly deformed systems like {sup 160}Gd{yields}{sup 160}Dy (87keV) and {sup 238}U{yields}{sup 238}Pu (44keV), which in turn test assumptions of the standard model of fundamental particles and interactions.« less
  • Collective gyromagnetic ratios g{sub R}, microscopically calculated from Hartree-Fock plus BCS calculations using the SkM{sup {asterisk}} force, are found to be very different from the rough Z/A estimates. It is pointed out that the latter disagree with the spectroscopic data in normally deformed states of even-even nuclei. The consequences of taking into account microscopic values of g{sub R} on the spectroscopic properties of odd superdeformed A=190 nuclei are discussed. Quenching factors, for proton and neutron g{sub s} ratios, are tentatively proposed. Single-particle assignments postulated by experimentalists for the available data are confirmed by our consistent approach. {copyright} {ital 1997} {italmore » The American Physical Society}« less
  • A method is proposed for describing the collective excitations of rotating nuclei that combines the cranking model and the random-phase approximation. The symmetries that are preserved for rotating nuclei and their connection with the physical states are discussed. The results of analysis of the properties of collective excitations in the framework of different models are presented.