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The new element 111 was produced and unambiguously identified in an experiment at SHIP, GSI Darmstadt. Three nudlei of the isotope 272111 were observed in irradiations of 2~ targets with a4Ni projectiles of 318 MeV and 320 MeV energy. The cross-sections are (1.72~ pb and (3.5_ +4-6) pb, respectively. The nuclei decay by cc emission into the new and so far the heaviest isotopes of the elements 109 and 107 with mass numbers A = 268 and A=264. The ~-decay chains were followed down to the known nuclei 260105 and 256Lr.

New neutron rich isotopes 267107Bh and 266107Bh were produced in bombardments of a 249Bk target with 117-MeV and 123-MeV 22Ne ions at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. Identification was made by observation of correlated alpha-particle decays between the Bh isotopes and their Db and Lr daughters using a rotating wheel system. 267Bh was produced with a cross section of approximately 70 pb and decays with a 17(+14)(-6) s half life by emission of alpha particles with an average energy of 8.83+/-0.03 MeV. One atom of 266Bh was observed, decaying within 1 s by emission of a 9.29-MeV alpha particle.

Abstract. In an experiment carried out to identify element 110, we have observed an ~-decay chain, that can be unambiguously assigned to zagll0. In a series of preexperiments the excitation functions of the fusion reactions S~176 and SSFe+Z~were measured with high precision in order to get the optimum projectile energies for the production of these heavy elements. The cross-section maxima of the In evaporation channels were observed at excitation energies of 15.6 MeV and 13.4 MeV, respectively. These data result in an optimum excitation energy of 12.3 MeV of the compound nucleus for the production of z69110 in the reaction nZNi + z~ + I n. In irradiations at the corresponding beam energy of 311 MeV we have observed a decay chain of 4 subsequent cc decays. This can be assigned to the isotope with the mass number 269 of the element 110 on the basis of delayed c~-~ coincidences. The accurately measured decay data of the daughter isotopes of the elements 108 to 102, obtained in the previous experiments, were used. The isotope z~'9110 decays with a half-life of ~'m+I.~0o,, /~s by emission of (11.1325:0.020) \ ~'"--120/ MeV alpha particles. The production cross-section is +6.2 (3,3_2.7) pb.