AyangeakaaAD072013D.pdf (9.87 MB)
Exotic Modes of Collective Excitations: Nuclear Tidal Waves and Chirality
thesis
posted on 2013-07-18, 00:00 authored by Akaa Daniel AyangeakaaTwo exotic modes of collective excitations of nuclei have been investigated in this work: the multiphonon excitations in the vibrational nucleus, 102Pd and the phenomenon of chirality in the 133Ce nucleus. The vibrational yrast states in 102Pd are described semiclassically as quadrupole running ('tidal') waves on the surface of the nucleus, and the propagating tidal wave interpreted as a rotating condensate of interacting, spin-aligned d bosons. The tidal wave concept has been investigated experimentally by measuring lifetimes of levels in the yrast band of the 102Pd nucleus using the Doppler shift attenuation method (DSAM). The extracted reduced transition probabilities, B(E2), for the yrast band display a monotonic increase with spin, in agreement with the interpretation based on rotation-induced condensation of aligned d-bosons, and the observed constant B(E2)/J ratios imply that the gain in angular momentum originates from the increase of the wave amplitude (deformation). In the second investigation, two distinct sets of chiral-doublet bands based on the three quasi-particle configurations π(1h11/2)2⊗ ν (1h11/2)-1 (higher-energy, negative parity) and π(1g7/2)-1(1h11/2)1 ⊗ν(1h11/2)-1 (lower-energy, positive parity) were identified in the nucleus 133Ce. The properties of these bands were observed to satisfy the established fingerprints of nuclear chirality and were found to agree with results of calculations based on a combination of the constrained triaxial relativistic mean field (RMF) theory and the particle-rotor model. They constitute a multiple chiral doublet (MχD), a phenomenon first predicted by RMF calculations. This study has provided the first experimental evidence for the existence of the MχD phenomenon, that represents, in general, a confirmation of triaxial shape coexistence.
History
Date Modified
2017-06-02Defense Date
2013-04-25Research Director(s)
U. GargCommittee Members
A.E. Livingstone X. Tang S. FrauendorfDegree
- Doctor of Philosophy
Degree Level
- Doctoral Dissertation
Language
- English
Alternate Identifier
etd-07182013-160311Publisher
University of Notre DameProgram Name
- Physics
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