Conférences et séminaires » Séminaire présenté par le Dr. Teng Lek Khoo, Argone National Laboratory
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Single-particle Spectrum, Shell Energy and Fission Barrier in Superheavy Nuclei
Par : Dr. Teng Lek Khoo, Argone National Laboratory
Date : mardi 19 octobre 2010 à 10h00
Lieu : IPHC, Salle de Réunion 2e étage du Bâtiment 27
The heaviest element with Z=118, which has been reported to have been synthesized in Dubna, represents a 44% extension beyond the last stable element Pb. This is a remarkable extension of the elements. Why is such a large extension possible ? What is the heaviest element which can exist ? What are the limits in E* and spin of superheavy nuclei (SHN) ? Are there doubly magic gaps beyond 208Pb and at which values of Z & N ? How well can theory predict the properties of SHN ? Can SHN provide tests of the most successful nuclear models ? To quantitatively answer these questions, one requires knowledge of the single-particle energies. Gaps in the spectrum give rise to the shell energy and extra binding responsible for the existence of superheavy nuclei (SHN) .
Single-particle energies have been deduced, which reproduce experimental 1-quasiparticle energies in heavy, odd-A nuclei. Comparisons with models, which successfully describe lighter nuclei, reveal serious shortcomings in the single-particle energies of density functional theories, highlighting the need for improved effective interactions and questioning their predictions of magic gaps for SHN. In contrast, the single-particle spectrum from the “universal” Woods-Saxon potential gives fair agreement, provided deformation parameters (up to at least β6) are chosen that minimize the total binding energy.
The binding from the shell energy creates a fission barrier, which otherwise would not exist for SHN. The shell energy and fission barrier at high spin provide new tests of models. The fission barrier of shell-stabilized 254No has been determined from measurements of the entry distribution, which extends to surprisingly large spin – beyond 30 ħ.
Personne à contacter : Radomira LOZEVA