Synthesis of heaviest elements (results and prospects)

The formation and decay properties of the heaviest nuclei with Z = 112 - 116 and 118 were studied in the reactions U-238, Pu-242,Pu-244, Am-243, Cm-245,Cm-248 and Cf-249+Ca-48. The new nuclides mainly undergo sequential alpha-decay, which ends with spontaneous fission. The total time of decays ranges from 0.5 ms to about 1 day, depending on the proton and neutron numbers in the synthesized nuclei. The atomic number of the new elements 115 and 113 was confirmed also by an independent radiochemical experiment based on the identification of the neutron-rich isotope (268)Db (T-SF approximate to 30 h) , the final product in the chain of alpha-decays of the odd-odd parent nucleus (288)115. The comparison of the decay properties of 29 new nuclides with Z = 104 - 118 and N = 162 - 177 gives evidence for the decisive influence of the structure of superheavy nuclei on their stability with respect to different modes of radioactive decay. The investigations connected with the search for superheavy elements in Nature (cosmic rays) and prospects of superheavy element research are also presented.