Superheavy nuclei

Abstract

The problem of the nuclear stability of superheavy chemical elements began to attract a great deal of attention soon after the methods of calculating their nuclear deformation energy had been developed and significant fission barriers had been predicted for superheavy nuclei having proton and neutron numbers close to the magic numbers Z=114 and N=184. Experiments to produce superheavy nuclei in heavy-ion reactions have so far been unsuccessful. It is not excluded that superheavy element (SHE) nuclei could be produced in deep inelastic transfer reactions involved in the system 248Cm+238U. Consideration of the mechanisms of nucleosynthesis and halflife calculations show that there is a small probability for superheavy nuclei to exist in nature. In studies of the tracks of cosmic-ray nuclei in meteoritic olivines some long tracks, supposedly due to nuclei with Z=110, have been observed. Their flux is nearly 300 times smaller than those of the thorium-uranium group nuclei. Searches for superheavy elements in some primitive meteorites and hot brines have resulted in the detection of a spontaneously fissioning nuclide, possibly belonging to a new island of stability. The low concentration of this nuclide makes its identification difficult. Searches should be made for geological samples whose formation process might lead to a greater concentration of the hypothetical superheavy elements relative to the average concentration in the Earth's crust.