The gamma-ray decay of new high spin states in ('25)Mg has been studied using the ('12)C(('14)N,p(gamma))('25)Mg reaction at E(lab) = 23.5 MeV. Proton-gamma coincidences were measured between an E (Si(Li))-(DELTA)E (Si) telescope arrangement at 0(DEGREES) to the beam and either of two Ge(Li) detectors at 90(DEGREES) or four gamma-ray detectors at 90(DEGREES), 81(DEGREES), 60(DEGREES) and 22(DEGREES) in an angular correlation experiment. Also, gamma-gamma coincidences were measured at 90(DEGREES). Experiments were performed at the Florida State University Super FN Tandem Van de Graaff accelerator, and one gamma-gamma coincidence measurement was performed at Triangle University Nuclear Laboratory. Twenty new neutron-unbound levels have been identified, with the range of possible spins narrowed to one or two possibilities for nine levels. / This research was performed to try and confirm the existence of "rotational coexistence" or equivalently "rotational isomerism" predicted to occur at J('(pi)) = 13/2('+) and 17/2('+) in ('25)Mg using the cranked Nilsson-Strutinsky formalism developed by Ingemar Ragnarsson, Tord Bengtsson and Sven Aberg at the Lund Institute of Technology. The same phenomenon has previously been identified with the yrast 8('+) state in ('24)Mg, where the eight units of angular momentum result from alignment of the spins of four s-d shell (valence) nucleons along the axis of rotation. The noncollective behavior of this state yields a prolate shape rotating parallel to the nuclear symmetry axis, and it is energetically favored relative to the prolate 8('+) ground state band member rotating perpendicular (collectively) to the symmetry axis. / Shell model calculations performed by Hobson Wildenthal at Drexel University, using an untruncated s-d shell basis space, have also been compared extensively with experiment. Based on the angular correlation results and correspondence with shell model and cranked Nilsson model predictions, tentative spin assignments have been made for the yrast 15/2('+), 17/2('+) and possibly 9/2('-) states, and the 13/2('+) and 15/2('+) ground state band members. The yrast 17/2('+) and previously observed 13/2('+) states are interpreted to be rotationally aligned, prolate shaped configurations. / Source: Dissertation Abstracts International, Volume: 48-02, Section: B, page: 0478. / Thesis (Ph.D.)--The Florida State University, 1987.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76050 |
| Contributors | HEADLY, DAVID MILES., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 343 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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