Göttingen 1997 – wissenschaftliches Programm
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HK: Hadronen und Kerne
HK 23: Kernspektroskopie, leichte Kerne II
HK 23.3: Gruppenbericht
Dienstag, 25. März 1997, 15:00–15:30, HS E
High-spin gamma-ray spectroscopy in the vicinity of 56Ni — •D. Rudolph1, C. Baktash2, M.J. Brinkman2, M. Devlin3, H.-Q. Jin4, D.R. LaFosse3, M. Leddy5, I.Y. Lee6, A.O. Macchiavelli6, L.L. Riedinger4, D.G. Sarantites3, and C.H. Yu2 — 1Ludwig-Maximilians-Universität München, D-85748 Garching — 2ORNL*, Oak Ridge, TN 37831, USA — 3Washington Univ., St. Louis, MO 63130, USA — 4Univ. of Tennessee, Knoxville, TN 37966, USA — 5Schuster Laboratory, Manchester M13 9PL, UK — 6LBNL, Berkeley, CA 94720, USA
The nuclei located around the doubly magic shell gap N=Z=28 have been extensively studied with light ion transfer reactions. With a proton scattering experiment in inverse kinematics the B(E2;2+→ 0+) in 56Ni [1] was measured recently, and the comparatively large value can be explained by the attractive interaction of 1f7/2 holes and 1f5/2 or 2p3/2 particles. However, high-spin spectroscopy in that mass A≈ 60 region has eked out a shadowy existence until now. Even though ground-state γ-ray transitions were reported for most of the nuclei, the excitation schemes comprise rather few high-spin levels — at most 5 to 10 if not less. Particular research objectives in that mass region are constraints on the spherical shell-model parameters, the observation of the predicted normally deformed and possibly superdeformed rotational bands, influence of the T=0 pairing in (odd-odd) N=Z systems, or the test of the isospin symmetry in medium-mass mirror nuclei.
We performed an experiment using the heavy-ion induced reaction 36Ar + 28Si at 136 MeV beam energy at the Gammasphere facility in conjunction with ancillary detectors to measure the evaporated neutrons, protons, and α-particles. Nearly 2·109 and 3·108 two- to four-fold gamma events were collected with thin and Ta-backed targets, respectively. The first experimental results include the identification of the Tz=−1/2 nucleus 55Ni (σrel≈ 0.004 %), and largely extended level schemes of the N=Z nuclei 52Fe, 54Co, and 58Cu. The near yrast levels in 55Co (mirror nucleus to 55Ni) are established up to spins of I≈ 18 ℏ at 15 MeV excitation energy. Latest results of the ongoing analysis will be presented and compared to theoretical calculations.
*Oak Ridge National Laboratory is managed by Lockheed Martin Research Corp. for the U.S. Department of Energy under contract DE-AC05-96OR22464.
[1] G. Kraus et al., Phys. Rev. Lett. 73, 1773 (1994).