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 2 = 114 and N = 184.Experiments to produce superheavy nuclei in heavy-ion reactions have so far been unsuccessful. However, some data show that the possibilities of producing cold compound nuclei were not used in the 48Ca-induced reactions. Therefore the corresponding experiments should be repeated. It is not excluded that superheavy element (SHE) nuclei could be produced in deep inelastic transfer reactions involved in the system Cm + 2 3 8 ~.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 2 = 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 (about g/g (1 part in in the Allende meteorite) 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. 248

Accelerator mass spectrometry – from DNA to astrophysics

“…An abundance limit of 10 -11 was found for 294 110 in Pt by assuming that the half-life was about 100 million years and the abundance in r-processed stellar material at the time of the formation of the solar system was 0.03 [28]. In none of the experiments [25][26][27] evidence for SHEs in nature was found.…”

“…Here only two recent applications of AMS in different fields (biomedicine and astrophysics) will be discussed: 14 C bomb peak dating of human DNA and the search for superheavy elements in nature, respectively. 27 Al(n,2n) 26 Al Reaction studies for nuclear astrophysics 10 Be, 14 C, 26 Al, 36 Radionuclides measured with AMS in the respective area of application [2]. Man-made radionuclides are underlined, and square brackets indicate a potential use in the future.…”

“…This may have to await neutron-rich projectiles from future radioactive-beam facilities. So far, the only way to search for a possible existence of these superheavy nuclides were searches in nature [25,26]. An early AMS experiment to search for the platinum homologue 294 110 (now 294 Ds) in a Pt placer nugget was performed at the tandem accelerator of the University of Pennsylvania [27].…”

Chemistry of superheavy elements

“…As first estimates yielded relatively long half-lives as long as a billion years, immediately a gold-rush period of hunting for superheavy elements (SHE) started, at first in nature -in terrestrial and extra-terrestrial samples -and later at accelerators. Reviews concentrating on various aspects of the experimental work of this early phase can be found in [11][12][13][14][15][16][17][18][19]. An overview over the first century of nuclear and radiochemistry is given in [20].…”

Synthesis of superheavy elements by cold fusion

“…Predicted half-lives based on calculations using various parameter sets differed by many orders of magnitude [4][5][6][7][8][9][10]. Some of the half-lives approached the age of the universe, and attempts have been made to discover naturally occurring SHEs [11,12]. Although the corresponding discoveries were announced from time to time, none of them could be substantiated after more detailed inspection.…”