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In bombardment of ${}^{244}\mathrm{Pu}$ with ${}^{48}\mathrm{Ca}$, we observed a decay sequence consisting of an implanted heavy atom, three subsequent $\ensuremath{\alpha}$ decays, and a spontaneous fission (SF), all correlated in time and position. The measured $\ensuremath{\alpha}$ energies and corresponding time intervals were ${E}_{\ensuremath{\alpha}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}9.71$ MeV ( $\ensuremath{\Delta}t\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}30.4$ s), 8.67 MeV ( $\ensuremath{\Delta}t\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}15.4$ min), and 8.83 MeV ( $\ensuremath{\Delta}t\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.6$ min); for the SF ( $\ensuremath{\Delta}t\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}16.5$ min), the total deposited energy was approximately 190 MeV. The $\ensuremath{\alpha}$-particle energies together with the decay times and SF terminating the chain offer evidence of the decay of nuclei with high atomic numbers. This decay chain is a good candidate for originating from the $\ensuremath{\alpha}$ decay of the parent nucleus ${}^{289}114$, produced with a cross section of about 1 pb.

In bombardments of ${}^{238}$U targets with 186-MeV ${}^{34}$S projectiles we discovered the $\ensuremath{\alpha}$-decaying nuclide ${}^{267}$108 with a half-life of ${19}_{\ensuremath{-}10}^{+29}$ ms, ${E}_{\ensuremath{\alpha}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}9.74$ to 9.87 MeV, and a production cross section of about 2.5 pb. The new nuclide was identified by measuring correlations in energy, time, and position to establish genetic links between its implantation in a position-sensitive silicon detector and subsequent $\ensuremath{\alpha}$ decay followed by $\ensuremath{\alpha}$ decays of known descendant nuclides.

Two years after the discovery of element 117, we undertook a second campaign using the (249)Bk+(48)Ca reaction for further investigations of the production and decay properties of the isotopes of element 117 on a larger number of events. The experiments were started in the end of April 2012 and are still under way. This Letter presents the results obtained in 1200 hours of an experimental run with the beam dose of (48)Ca of about 1.5×10(19) particles. The (249)Bk target was irradiated at two energies of (48)Ca that correspond to the maximum probability of the reaction channels with evaporation of three and four neutrons from the excited (297)117. In this experiment, two decay chains of (294)117 (3n) and five decay chains of (293)117 (4n) were detected. In the course of the long-term work, (249)Cf-the product of decay of (249)Bk (330 d)-is being accumulated in the target. Consequently, in the present experiment, we also detected a single decay of the known isotope (294)118 that was produced during 2002-2005 in the reaction (249)Cf((48)Ca,3n)(294)118. The obtained results are compared with the data from previous experiments. The experiments are carried out in the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, using the heavy-ion cyclotron U400.

Results of a new series of experiments on the study of production cross sections and decay properties of the isotopes of element 115 in the reaction $^{243}\mathrm{Am}+^{48}\mathrm{Ca}$ are presented. Twenty-one new decay chains originating from $^{288}115$ were established as the product of the $3n$-evaporation channel by measuring the excitation function at three excitation energies of the compound nucleus $^{291}115$. The decay properties of all newly observed nuclei are in full agreement with those we measured in 2003. At the lowest excitation energy ${E}^{*}=33\text{ }\text{ }\mathrm{MeV}$, for the first time we registered the product of the $2n$-evaporation channel, $^{289}115$, which was also observed previously in the reaction $^{249}\mathrm{Bk}+^{48}\mathrm{Ca}$ as the daughter nucleus of the decay of $^{293}117$. The maximum cross section for the production of $^{288}115$ is found to be 8.5 pb at ${E}^{*}\ensuremath{\approx}36\text{ }\text{ }\mathrm{MeV}$.

Results of a new series of experiments on the study of production cross sections and decay properties of the isotopes of element 115 in the reaction (243)Am+(48)Ca are presented. Twenty-one new decay chains originating from (288)115 were established as the product of the 3n-evaporation channel by measuring the excitation function at three excitation energies of the compound nucleus (291)115. The decay properties of all newly observed nuclei are in full agreement with those we measured in 2003. At the lowest excitation energy E*=33 MeV, for the first time we registered the product of the 2n-evaporation channel, (289)115, which was also observed previously in the reaction (249)Bk+(48)Ca as the daughter nucleus of the decay of (293)117. The maximum cross section for the production of (288)115 is found to be 8.5 pb at E*≈36 MeV.

The discovery of a new chemical element with atomic number Z=117 is reported. The isotopes {sup 293}117 and {sup 294}117 were produced in fusion reactions between {sup 48}Ca and {sup 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{>=}111, validating the concept of the long sought island of enhanced stability for superheavy nuclei.