Conférences et séminaires » Séminaire présenté par le Pr. R.K. Gupta (Physics Department, Panjab (...)
Dernière mise à jour
Theory of compactness in hot fusion reactions for super-heavy elements.
le Mardi 27 mars 2007 à 16 h00
Salle de Visioconférences - Bâtiment 25
IPHC, 23 rue du Loess, Strasbourg-Cronenbourg
The compactness of hot fusion reactions, indicated in 48Ca induced reactions on various actinides such as 238U and 242, 244Pu, is studied for super-heavy nuclei 110Ds to Z=118 on the basis of the quantum mechanical fragmentation theory (QMFT) extended to include the orientation degrees of freedom θ and higher multi-pole deformations βλ, up to hexadecupole deformations β4. For hot fusion reactions, the barrier is highest and for these reactions to be compact, the interaction radius is smallest. It is shown that the reactions leading to Z 114 nuclei are “compact” hot fusion reactions at θ = 90° (equatorial compact, ec, i.e., the collisions occur in the direction of the minor axis of the deformed reaction partner), but the ones for Z < 114 nuclei are “compact” at θ < 90° (not-equatorial compact, nec). This phenomenon of “barrier distribution in orientation degree of freedom” is observed for the first time to be related to the magnitudes of both the quadrupole and hexadecupole deformations of the deformed reaction partner. The “ec” configurations are obtained for the cases of quadrupole deformation alone and with small (including negative values) hexadecupole deformations. The presence of large (positive) hexadecupole deformations result in the “nec” configurations. In addition to the 48Ca reaction valley, a number of other new reaction valleys (target-projectile combinations) are obtained for compact hot fusion reactions, the most important one (next to 48Ca) being the 54Ti nucleus used earlier in Pb-based cold fusion reactions but now with the deformed actinide nuclei like 226Ra, 232Th, 238U and 242Pu, etc. Furthermore, within the QMFT based dynamical cluster-decay model (DCM), the fusion excitation functions of 238U(48Ca,xn)286-x112 and 244Pu(48Ca,xn)292-x114 reactions are nicely obtained in terms of a single length parameter. The role of the static deformation of the target nucleus and its orientation at the point of collision is also studied.
Personnes a contacter :