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It is often assumed that the nucleus of an atom is spherical; however, this is not always the case. At excited or high-spin states, where the nucleus is rotating very rapidly, it can either stretch or compress along a body-fixed, principal axis, giving it the shape of an American football or a doorknob. Very rarely, a nucleus can assume an asymmetric shape where it does not rotate around a principal axis but instead wobbles. This wobbling motion is analogous to the spinning motion of an asymmetric top. The wobbling mode has been found in several isotopes of lutetium (Lu). Surprisingly, this mode was not observed in the neighboring hafnium (Hf) and thulim (Tm) isotopes and was only recently found in an isotope of tantalum (Ta). The observation of a wobbling band, associated with the i13/2 band is a strong indication that a nucleus possesses asymmetric deformation. In order to determine the role of the atomic number on the observation of asymmetric deformation, an experiment was conducted to search for the wobbling mode in 171Re. High-spin states in 171Re were produced in a reaction at Argonne National Laboratory. The off-center collisions between the 55Mn beam and the 120Sn target nuclei resulted in large amounts of angular momentum (spin) in the new compound nucleus. To dispel this angular momentum, rays were emitted by the nucleus; these rays were detected using germanium detectors in the Gammasphere spectrometer at Argonne National Laboratory. These gamma ray data were subsequently analyzed at the Naval Academy. Gamma rays that were emitted in coincidence, or nearly simultaneously, came from one unpaired nucleon in its decay to the ground state. Seven decay sequences in 171Re were established, but the focus of this project was based on sequences feeding into the previously determined i13/2 band. Two bands were found to feed into the i13/2 structure, and their characteristics have been assessed to determine if these sequences are associated with wobbling., The original document contains color images.

High-angular-momentum states in Zn-64 were populated in the Ca-40(Si-28,4p) reaction at a beam energy of 122 MeV. Evaporated, light, charged particles were identified by the Microball, while gamma rays were detected using the Gammasphere array. The main focus of this paper is on two strongly coupled, collective bands. The yrast band, which was previously known, has been linked to lower-lying states establishing the excitation energies and angular momenta of in-band states for the first time. The newly identified excited band decays to the yrast band but firm angular-momentum assignments could not be made. In order to interpret these structures cranked-Nilsson-Strutinsky calculations have been performed. The calculations have been extended to account for the distribution of nucleons within a configuration. The yrast collective band is interpreted as based on the pi(f(7/2))(-1)(p(3/2)f(5/2))(2)(g(9/2))(1)nu(p(3/2)f(5/2))(4)(g(9/2))(2) configuration. There are several possible interpretations of the second band but it is difficult to distinguish between the different possibilities., QC 20100525 QC 20111027

Superdeformed bands in Mo-88 and Tc-89 were populated Using Ca-40-induced fusion-evaporation reactions on Ni-58 at a beam energy of 185 MeV. Gamma-rays emitted in the reactions were detected using the Gammasphere spectrometer, in coincidence with charged particles detected by the Microball array. A new superdeformed band was assigned to the nucleus Mo-88, leading to a revisit of earlier configuration assignments for superdeformed structures in this nucleus. In particular, the theoretical interpretation of a pair of identical (isospectral) superdeformed bands in Mo-88/Tc-89 is discussed. The configurations that are assigned to the four SD bands belonging to Mo-88 have properties that are predicted to be significantly affected by pair correlations., QC 20100525 QC 20110923

Superdeformed bands in Mo-88, Tc-89, and Tc-91 were populated using a Ca-40 beam with an energy of 185 MeV, impinging on a backed Ni-58 target. gamma rays and charged particles emitted in the reactions were detected using the Gammasphere Ge detector array and the CsI(TI) array Microball. Average transition quadrupole moments Q(t) with significantly improved accuracy compared to earlier work, were deduced for the bands using the residual doppler shift technique. The experimental results were included into a systematic study of the Q(t) values throughout the superdeformed mass 80-90 region. The superdeformed shell gaps are predicted to move towards larger deformations with increasing Z and N in this mass region. This trend is confirmed by the experimental Q(t) values., QC 20100525

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., QC 20100525