Level statistics of near-yrast states in rapidly rotating nuclei |
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| Affiliation: | 1. Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-01, Japan;2. Niels Bohr Institute, University of Copenhagen, Copenhagen Ø, Denmark;3. INFN sez. Milano, University of Milan, Milan, Italy;4. Department of Mathematical Physics, Lund Institute of Technology, Lund, Sweden;1. Nuclear Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA 94720, USA;2. Physics Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37831, USA;3. Nuclear Security and Isotope Technology Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37831, USA;4. Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 7ZE, United Kingdom;1. University of Liverpool, Oliver Lodge Building, Liverpool, L69 7ZE, UK;2. STFC, Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, UK;3. Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA;1. Department of Nuclear Physics, RSPE, Australian National University, Canberra, ACT 2601, Australia;2. Nuclear Engineering Division, Argonne National Laboratory, Argonne, IL 60439, USA;3. Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA;4. Department of Physics, University of Massachusetts Lowell, Lowell, MA 01854, USA;5. School of Physics, Peking University, Beijing 100871, China;6. RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan;1. AWE, Aldermaston, Reading, Berkshire RG7 4PR, UK;2. University of Surrey, Guildford GU2 7XH, UK |
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| Abstract: | The nearest neighbour level spacing distribution and the Δ3 statistic of level fluctuations associated with very high spin states (I ≳ 30) in rare-earth deformed nuclei are analysed by means of a cranked shell model. The many particle-many hole configurations created in the rotating Nilsson potential are mixed by the surface-delta two-body residual interaction. The levels in the near-yrast region show a Poisson-like level spacing distribution. As the intrinsic excitation energy U increases, the level statistics shows a gradual transition from order to chaos, reaching at U ≳ 2 MeV the Wigner distribution typical-of the Gaussian orthogonal ensemble of random matrices. This transition is caused by the residual two-body interaction. On the other hand, the level spacings between the yrast and the first excited state show a peculiar behaviour, displaying a Wigner-like distribution instead of the Poisson-like distribution seen for the other near-yrast rotational states. The lowest spacings reflect the properties of the single-particle orbits in the mean-field, and are only weakly affected by the residual two-body interaction. |
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