Synthesis of elements 115 and 113 in the reaction 243Am + 48Ca
The results of two experiments designed to synthesize element 115 isotopes in the {sup 243}Am+{sup 48}Ca reaction are presented. Two new elements with atomic numbers 113 and 115 were observed for the first time. With 248-MeV {sup 48}Ca projectiles, we observed three similar decay chains consisting of five consecutive {alpha} decays, all detected in a total time interval of 30 s. Each chain was terminated by a spontaneous fission (SF) with a high-energy release and a lifetime of about a day. With 253-MeV {sup 48}Ca projectiles, we registered a different decay chain of consecutive {alpha} decays detected in a time interval of 0.5 s, also terminated by spontaneous fission, but after 1.8 h. The decay properties of the eleven new {alpha}- and SF-decaying nuclei are consistent with expectations for consecutive {alpha} decays originating from the parent isotopes {sup 288}115 and {sup 287}115, produced in the 3n- and 4n-evaporation channels, respectively. Support for the assignment of the atomic numbers of all of the nuclei in the {sup 288}115 decay chain was obtained in an independent experiment in which a long-lived spontaneous fission activity, {sup 268}Db (15 events), was found to be chemically consistent with the fifth group of the periodic table.more » The odd-odd isotope {sup 288}115 was observed with largest cross section of about 4 pb. In the SF decay of {sup 268}Db, a total kinetic energy of 230 MeV and a neutron multiplicity per fission of 4.2 were measured. The decay properties of the 11 new isotopes with Z=105-115 and the production cross sections are in agreement with modern concepts of the role of nuclear shells in the stability of superheavy nuclei. The experiments were carried out at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research.« less

title: Synthesis of the New Element with Z=117
abstract: The synthesis of the new chemical element with atomic number Z=117 is presented. The isotopes 293117 and 294117were produced in fusion reactions between 48Ca and 249Bk. The 249Bk was produced in the High Flux Isotope Reactor and chemically separated at Oak Ridge. Decay chains involving eleven new nuclei were identified by means of the Dubna Gas Filled Recoil Separator. The measured decay properties show a strong rise of stability for super-heavy nuclei toward N=184.

title: Synthesis of a new element with atomic number Z = 117.
abstract: The discovery of a new chemical element with atomic number Z=117 is reported. The isotopes (293)117 and (294)117 were produced in fusion reactions between (48)Ca and (249)Bk. Decay chains involving 11 new nuclei were identified by means of the Dubna gas-filled recoil separator. The measured decay properties show a strong rise of stability for heavier isotopes with Z > or = 111, validating the concept of the long sought island of enhanced stability for superheavy nuclei.

title: Measurements of cross sections for the fusion-evaporation reactions pu-244(ca-48, xn) 114-(292-x) and cm-245(ca-48, xn) 116-(293-x)
abstract: We have studied the excitation functions of the reactions 244Pu(48Ca,xn). Maximum cross sections for the evaporation of 3–5 neutrons in the complete-fusion reaction 244Pu+48Ca were measured to be s3n=2 pb,s4n =5 pb, ands5n=1 pb. The decay properties of 3 n-evaporation product 289114, in the decay chains observed at low 48Ca energy coincide well with those previously observed in the 244Pu+48Ca and248Cm+48Ca reactions and assigned to288114. Two isotopes of element 114 and their descendant nuclei were identified for the first time at higher bombarding energies: 288114 (Ea=9.95 MeV, T1/2=0.6 s) and 287114 (Ea=10.04 MeV,T1/2 =1 s). We also report on the observation of new isotopes of element 116, 290,291116, produced in the245Cm +48Ca reaction with cross sections of about 1 pb. A discussion of self-consistent interpretations of all observed decay chains originating at Z=118, 116, and 114 is presented.

title: Experiments on the synthesis of element 115 in the reaction am-243(ca-48, xn) x-115-291

title: Synthesis of the isotope 282 113 in the Np237+Ca48 fusion reaction
abstract: The decay properties of the new isotope ${}^{282}113$ and its daughter nuclei have been measured in the $^{237}\mathrm{Np}$($^{48}\mathrm{Ca}$, $3n$)${}^{282}113$ reaction. During an irradiation with a beam dose of $1.1\ifmmode\times\else\texttimes\fi{}{10}^{19}244$-MeV $^{48}\mathrm{Ca}$ projectiles, two decay chains originating from the odd-odd isotope ${}^{282}113$ $({E}_{\ensuremath{\alpha}}=10.63\ifmmode\pm\else\textpm\fi{}0.08\phantom{\rule{0.3em}{0ex}}\mathrm{MeV},{T}_{\ensuremath{\alpha}}={73}_{\ensuremath{-}29}^{+134}\phantom{\rule{0.3em}{0ex}}\mathrm{ms})$ were produced in the complete fusion reaction with a cross section of $0.{9}_{\ensuremath{-}0.6}^{+1.6}$ pb; these properties are all in agreement with expectations based on the results of previous experiments.

title: Experiments on synthesis of superheavy nuclei by reactions with Ge ions