NUCLIDES FAR OFF THE STABILITY LINE AND SUPER-HEAVY NUCLEI IN HEAVY-ION NUCLEAR REACTIONS

Abstract

A review is given on the new species which have been produced in the recent years by heavy ion reactions, mainly 12C, 16O, 18O, 22Ne and 20Ne ions. The first section is devoted to the formation of neutron rich exotic light nuclei and to the mechanism of multinuclear transfer reactions responsible for this formation. In the second section dealing on medium atomic numbers a brief account is made on the discovery of proton radioactivity and some comments are made on the difficulties encountered for producing very neutron deficient isotopes like 10050Sn. The study of the region of neutron deficiency for rare earth is one of the most fruitful field for heavy ion reactions. More than fifty new isotopes have been found. A discussion is made on the possibility for going further into the neutron deficiency open by the use of Ar, Kr and heavier ions. It is shown that there is no advantage to bombard targets with ions heavier than 40Ca or 58Ni. Section 4 is devoted to heavy nuclei in the region of the neutron shell N = 126. Fission competition is discussed as well as the limitation of the compound nucleus cross section due to high angular momentum effects. Results are presented on the rotating liquid drop and the very strong diminution of fission barriers due to rotational energy. A brief review is made of the new decay families discovered by Hyde et al. [63] for light thorium and protactinium isotopes. These results are one of the great success of heavy-ion induced reactions. Section 5 reminds that all isotopes of elements beyond Z = 101 have been produced by heavyion reactions, in spite of the great fission competitionc. The last section describes the various attempts already made for the synthesis of superheavy elements. A discussion is presented on the following problems : reaction thresholds and coulomb barriers for heavily charged projectiles, complete fusion cross section as compared to the total cross section, main decay channels for excited compound nuclei in the region Z = 118, N = 184-190, fusion-fission reactions and the possibility of production of S.H. elements as fission fragments, grazing reactions and exchange of big aggregates.