C. Beck

CLUSTERS IN LIGHT NUCLEI

C+ Cmolec-ularresonances. Ourknowledgeinthephysicsofnuclearmoleculeshasin-creasedconsiderablyandnuclearclusteringremainsoneofthemostfruitfuldomainsofnuclearphysics,facingsomeofthegreatestchallengesandop-portunities in the years ahead. In this work, the occurence of “exotic”shapesinlightN= Z -likenucleiisinvestigated. Variousapproachesofsuperdeformed and hyperdeformed bands associated with quasimolecularresonant structures are presented. Results on clustering aspects are alsodiscussedforlightneutron-richoxygenisotopes.

Multi-neutron transfer coupling in sub-barrier 32S + 90,96Zr fusion reactions

The role of neutron transfers is investigated in the fusion process below the Coulomb barrier by ana- lyzing 32 S+ 90 Zr and 32 S+ 96 Zr as benchmark reactions. A full coupled-channel calculation of the fusion excitation functions has been performed for both systems by using multi-neutron transfer coupling for the more neutron- rich reaction. The enhancement of fusion cross sections for 32 S+ 96 Zr is well reproduced at sub-barrier energies by NTFus code calculations including the coupling of the neutron-transfer channels following the Zagrebaev semiclassical model. We found similar effects for 40 Ca+ 90 Zr and 40 Ca+ 96 Zr fusion excitation functions.

The STELLA apparatus for particle-Gamma coincidence fusion measurements with nanosecond timing

The STELLA (STELlar LAboratory) experimental station for the measurement of deep sub-barrier light heavy-ion fusion cross sections has been installed at the Andromede accelerator at the Institut de Physique Nucleaire, Orsay (France). The setup is designed for the direct experimental determination of heavy-ion fusion cross sections as low as tens of picobarn. The detection concept is based on the coincident measurement of emitted gamma rays with the UK FATIMA (FAst TIMing Array) and evaporated charged particles using a silicon detector array. Key developments relevant to reaching the extreme sub-barrier fusion region are a rotating target mechanism to sustain beam intensities above 10μA, an ultra-high vacuum of 10−8 mbar to prevent carbon built-up and gamma charged-particle timing in the order of nanoseconds sufficient to separate proton and alpha particles.

12C+16O sub-barrier radiative capture cross-section measurements

We have performed a heavy ion radiative capture reaction between two light heavy ions, 12 C and 16 O, leading to 28 Si. The present experiment has been performed below Coulomb barrier energies in order to reduce the phase space and to try to shed light on structural eects. Obtained -spectra display a previously unobserved strong feeding of intermediate states around 11 MeV at these energies. This new decay branch is not fully reproduced by statistical nor semi-statistical decay scenarii and may imply structural eects. Radiative capture cross-sections are extracted from the data.