Angular Momentum Induced Shape Changes in the Rare-Earth Nuclei ¹⁵²,¹⁵³Gd and ¹⁵⁹,¹⁶⁰Yb

The technique of studying nuclear structure under the rigors of high angular momentum through the examination of γ-ray cascades has recently undergone an explosion in productivity. These advances have been brought on primarily by the development of new detection systems, such as GAMMASPHERE, which are comprised of numerous individual elements. When these Compton-suppressed Ge detectors are operated in unison, a remarkable ability to distinguish weak and exotic changes in structure emerges. The current generation of spectrometers have allowed dramatic insight into the nucleus and are eclipsed only by the promises of arrays currently on the horizon. The fundamentals of employing γ-ray spectroscopic techniques to examine the fascinating behavior of rapidly rotating nuclei using these arrays will be discussed. The rare earth region of the nuclear landscape is a significant expanse of heavy nuclei with varying degrees of shell occupation. The region has proven to be a rich environment for studying nuclear structure at high spin. For example, superdeformation, identical bands, and backbending were all discovered in this region. This work explores the advances made on four nuclei from this region: 152,153Gd and 159,160Yb. Extensive additions to the previously known structure were made for each nucleus, exposing an unexpected similarity between 152Gd and 154Dy. Long sought after evidence of an angular momentum induced change in nuclear shape was found for each of the nuclei. This shift, from prolate collective rotation at low spin to oblate single particle behavior at high spin, represents a dramatic change in the method employed by the nucleus to generate angular momentum.