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[en] The definition of stable and unstable elements is recalled and the reasons for the instability of some nuclei are analyzed. The radioactivity phenomenon (in particular that of heavy nuclei) is described and it is shown how first transuranium elements were obtained The limit to the existence of too heavy nuclei is discussed and experiments with heavy ion beams carried out to produce transuranium elements are presented
[fr]Apres avoir rappele ce que sont les elements stables et instables, etudie les causes d'instabilite de certains noyaux et le phenomene de radioactivite, en particulier la radioactivite des noyaux lourds, on a montre comment ont ete obtenus les premiers elements transuraniens. On a essaye de definir la limite d'existence des noyaux trop lourds et montre l'espoir que suscite les accelerateurs a ions lourds pour la production des elements transuraniens
[en] The research group at the Gesellschaft fuer Schwerionenforschung highly appreciates the efforts of the International Union of Applied Chemistry and the International Union of Applied Physics to solve the longstanding problem of the priority of discovery of the heaviest elements by appointing the Transfermium Working Group. This international group of renowned experts in nuclear physics and chemistry, headed by Sir Denys Wilkinson, established criteria for the discovery of a new element and on the basis judged on the priorities of the discoveries of the transfermium elements. Members of this group were scientists from countries not involved in the discovery of a new element. The criteria for the discovery of new elements were developed after a careful study of the literature and after visits to the involved laboratories. Permanent contact was established with the researchers concerned by distributing the protocols of the TWG meetings. Only this procedure made it possible that the criteria were adapted to the most recent experimental developments. (Author)
[en] Fusion – fission probabilities in the synthesis of heaviest elements are discussed in the context of the latest experimental reports. Cross sections for superheavy nuclei are evaluated using the “Fusion by Diffusion” (FBD) model. Predictive power of this approach is shown for experimentally known Lv and Og isotopes and predictions given for Z = 119, 120. Ground state and saddle point properties as masses, shell corrections, pairing energies, and deformations necessary for cross-section estimations are calculated systematically within the multidimensional microscopic-macroscopic method based on the deformed Woods-Saxon single-particle potential. In the frame of the FBD approach predictions for production of elements heavier than Z = 118 are not too optimistic. For this reason, and because of high instability of superheavy nuclei, we comment on some structure effects, connected with the K-isomerism phenomenon which could lead to a significant increase in the stability of these systems.