Search

We report the experimental confirmation of the production of element 110. In the bombardment of a 208Pb target with a 309-MeV 64Ni beam, we have observed two chains of time- and position-correlated events. Each chain consisted of the implantation of an evaporation residue followed by the emission of α particles. We attribute these two chains to the decay of 271110 produced with a cross section of 8.3−5.3+11pb.

Development of chemical separations for the transactinides has traditionally been performed with longer-lived tracer activities purchased commercially. With these long-lived tracers, there is always the potential problem that the tracer atoms are not always in the same chemical form as the short-lived atoms produced in on-line experiments. This problem is especially severe for elements in groups 4 and 5 of the periodic table, where hydrolysis is present. The long-lived tracers usually are stored with a complexing agent to prevent sorption or precipitation. Chemistry experiments performed with these long-lived tracers are therefore not analogous to those chemical experiments performed in on-line experiments. One way to eliminate the differences between off-line and on-line chemistry experiments is through the use of a sup 2 sup 5 sup 2 Cf fission fragment collection device. A sup 2 sup 5 sup 2 Cf fission fragment collection device has already been constructed [1]. This device is limited in its capabilities. A new fission fragment device would allow the study of the chemical properties of the homologues of the heaviest elements. This new device would be capable of producing fission fragments for fast gas chemistry and aqueous chemistry experiments, long-lived tracers for model system development and neutrons for neutron activation. Fission fragment activities produced in this way should have the same chemical form as those produced in Cyclotron irradiations. The simple operation of this source will allow more rapid and reliable development of radiochemical separations with homologues of transactinide elements.

New neutron rich isotopes 107267Bh and 107266Bh 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 α-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 ≈70 pb and decays with a 17−6+14 s half life by emission of α 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 α particle.

Following a prediction by Smolańczuk [Phys. Rev. C 59, 2634 (1999)], we searched for superheavy element formation in the bombardment of 208Pb with 449-MeV 86Kr ions. We have observed three decay chains, each consisting of an implanted heavy atom and six subsequent α decays, correlated in time and position. In these decay chains, a rapid (ms) sequence of high energy α particles ( Eα≥10MeV) indicates the decay of a new high- Z element. The observed chains are consistent with the formation of 129318 and its decay by sequential α-particle emission to 128916, 128514, 128112, 127710, 273Hs ( Z=108) and 269Sg ( Z=106). The production cross section is 2.2−0.8+2.6pb.