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HK: Physik der Hadronen und Kerne

HK 16: Nuclear Structure/Spectroscopy II

HK 16.2: Gruppenbericht

Dienstag, 9. März 2004, 16:00–16:30, A

New Insights into the Fission Barrier Landscape of Light Actinides^* — •P.G. Thirolf¹, M. Csatlós², T. Faestermann³, G. Graw¹, D. Habs¹, J. Gulyás², M.N. Harakeh⁴, R. Hertenberger¹, M. Hegelich¹, M. Hunyadi², A. Krasznahorkay², H.J. Maier¹, Z. Máté², J. Szerypo¹, and H.-F. Wirth¹ — ¹Ludwig-Maximilians-Universität München — ²Inst. of Nucl. Res. of the Hung. Acad. of Sci., Debrecen — ³Technische Universität München — ⁴Kernfysisch Versneller Instituut, Groningen

Transmission resonance spectroscopy in ²³⁶U has been performed with high resolution, resulting in the identification of rotational band structures corresponding to hyperdeformed configurations. From the level density an excitation energy of the ground state in the third minimum of 3.30±0.4 MeV could be determined [1], thus confirming the existence of a rather deep third minimum, similar to our previous findings in ²³⁴U [2]. The excitation energy of the lowest hyperdeformed transmission resonance and the energy dependence of the fission isomer population probability enabled the determination of the height of the inner fission barrier E_A=5.15 ±0.20 MeV. This significant lowering of the inner barrier height compared to previously believed values in the presence of a deep third well may be a general feature in the light actinides, giving rise to the existence of short-lived fission isomers. First experiments searching for ps shape isomers in light uranium isotopes will be presented. [1] M. Csatlós et al., submitted to Phys. Lett.
[2] A. Krasznahorkay et al., Phys. Lett. B461 (1999) 15.
^* Supported by the DFG and Maier-Leibnitz-Laboratorium, Garching