Conférences et séminaires » Séminaire présenté par le Dr. Neil ROWLEY, IPN, Orsay
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Entrance-channel effects in the fusion and quasi-fission of heavy nuclei
Par : Dr. Neil ROWLEY, IPN, Orsay
Date : vendredi 9 novembre 2012 à 10h
Lieu : IPHC, Salle de Réunion 2e étage du Bâtiment 27
Over 100 years ago, Rutherford et al. performed the first ever set of experiments on nuclear reactions. By scattering the mono-energetic alpha particles emanating from a radioactive source on various metallic foils, they were able to prove the existence of the atomic nucleus and to obtain a measure of its radius.
Today, we perform experiments that are similar in spirit but, with access to heavier beams of variable-energy, we generally prefer to measure the complementary process of fusion. Reactions between rotational and vibrational nuclei will give rise to a range of radii, with a corresponding "fusion barrier distribution" whose form is intimately related to the static and dynamical deformations of the target and projectile. The realization that this distribution can be obtained directly from sufficiently precise experimental data has led to enormous insights into the interplay of nuclear structure and nuclear reaction mechanisms.
The production of very heavy and super-heavy compound nuclei must be performed in a narrow energy window close to the Coulomb barrier, since at lower energies the fusion cross section becomes vanishingly small, and at higher energies the fission probability totally dominates. This renders the cross sections and spin distributions of these systems particularly sensitive to their barrier distributions. This is especially important when the quasi-fission mechanism comes into play ; that is, a rapid re-separation into highly damped fragments with masses similar to those of the target and projectile, rather than the desired evolution into an equilibrated compound nucleus.
Personne à contacter : Radomira LOZEVA