Bochum 2018 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 58: Structure and Dynamics of Nuclei X
HK 58.1: Gruppenbericht
Freitag, 2. März 2018, 14:00–14:30, HZO 70
Level densities and broken axial symmetry in stable heavy nuclei — •Eckart Grosse1 and Arnd R. Junghans2 — 1Institute of Nuclear and Particle Physics, Technische Univ. Dresden, 01062 Dresden, Germany — 2Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany
From spectroscopic information for (especially odd) heavy nuclei and from multiple Coulomb excitation more and more hints on broken axial symmetry in nuclei also in the valley of stability have been found. But in quasi all prescriptions for the prediction of level densities axial symmetry is assumed ad hoc and thus it is important to investigate the consequence of symmetry breaking, e.g. by a tri-axial Fermi gas model like the TLO used for IVGDR shapes [EPJA 53(2017)225].
For excitation energies above 20 MeV a comparison of state densities from the Fermi gas approach to those extracted from combinatorial considerations indicates discrepancies which cannot be removed by a modification of the back-shift energy, but by the use of a reduced 'level density' parameter â, in accordance to nuclear matter studies.
At low energy a test using the accurately determined spacings of neutron capture resonances indicates a similar result, but for even targets only spin 1/2 states are populated for which the a spin cut-off is unimportant. Using recent results from measurements at the Oslo cyclotron the non-axial Fermi gas model proposed is verified now also for higher spin values in variously deformed nuclei.