We describe the discoveries of new superheavy nuclei (a) with Z = 107-112 produced in cold fusion reactions between 208 Pb and 209 Bi and beams of A > 50 and (b) with Z = 113-118 in hot fusion reactions between actinide nuclei and 48 Ca. We also discuss the facilities used in these measurements. We compare the behavior of the α-decay energies and half-lives, spontaneous fission half-lives, cross sections, and excitation functions with expectations from theoretical calculations. Finally, we outline future research directions, including studies of the detailed properties of nuclei synthesized at higher yields, searches for new elements with Z = 119 and 120, and developments of new facilities.

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The level structure of 7 Se was investigated via the decay of Br produced in the Ni ("O,pn) reaction. 32 transitions were assigned to Se on the basis of half-life, energy, and/ or relative y-ray yields for different beam energies with 18 transitions confirmed by coincidence data. 32 transitions are placed into the decay scheme which consists of the following levels: 862.0, 3225.9; and 3239.5 keV. The half-life of~~B r was measured to be 1.31+ 0.04 min. RADIOACTIVITY +Br; measured Tii2, E&, I&, pp coin. Se deduced levels, Jp.

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Two new alpha emitters 109Xe and 105Te were identified through the observation of the 109Xe --> 105Te --> 101Sn alpha-decay chain. The 109Xe nuclei were produced in the fusion-evaporation reaction 54Fe(58Ni,3n)109Xe and studied using the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility. Two transitions at Ealpha = 4062 +/- 7 keV and Ealpha = 3918 +/- 9 keV were interpreted as the l = 2 and l = 0 transitions from the 7/2+ ground state in 109Xe (T1/2 = 13 +/- 2 ms) to the 5/2+ ground state and a 7/2+ excited state, located at 150 +/- 13 keV in 105Te. The observation of the subsequent decay of 105Te marks the discovery of the lightest known alpha-decaying nucleus. The measured transition energy Ealpha = 4703 +/- 5 keV and half-life T1/2 = 620 +/- 70 ns were used to determine the reduced alpha-decay width delta2. The ratio delta105Te(2)/delta213Po(2) of approximately 3 indicates a superallowed character of the alpha emission from 105Te.

: A new type of decay corresponding to the neutronless 10 Beaccompanied fragmentation of 252 Cf is studied. We employ a cluster model similar to the model used for the description of cluster radioactivity. No preformation factors were considered. The ternary relative isotopic yields were calculated as the ratio of the penetrability of a given ternary fragmentation over the sum of penetrabilities of all possible ternary neutronless fragmentations. The corresponding barriers between the light and heavy fragment and between the 10 Be cluster and the two heavier fragments were computed with the help of a double folding potential generated by M3Y-NN effective interaction and realistic fragment ground state deformations. Also, we studied the influence of the fragment excitation energies on the yields, by including the level densities and the β-stretching of the fragments. The new phenomenon could be experimentally observed by the triple gamma coincidence technique between the fragments and 10 Be.PACS number : 25.85.Ca,27.90.+b

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