Following a prediction by Smolanczuk [Phys. Rev. C 59, 2634 (1999)], we searched for superheavy element formation in the bombardment of Pb-208 With 449-Mev Kr-86 ions. We have observed three decay chains, each consisting of an implanted heavy atom and six subsequent alpha decays, correlated in time and position. In these decay chains, a rapid (ms) sequence of high energy alpha particles (E-alpha greater than or equal to 10 MeV) indicates the decay of a new high-Z element. The observed chains are consistent with the formation of (293)118 and its decay by sequential alpha-particle emission to (289)116, (285)114, (281)112, (277)110, (273)Hs (Z = 108) and (269)Sg (Z = 106). The production cross section is 2.2(-0.8)(+2.6) pb.

{sup 224}Pa was produced via the {sup 209}Bi({sup 18}O,3n) reaction at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron and the half-life was determined to be 850{plus_minus}20 ms by measuring its alpha decay using our rotating wheel system. Our value is consistent with a previously reported half-life of 950{plus_minus}150 ms for {sup 224} Pa produced via the {sup 205}Tl({sup 22}Ne,3n) reaction, but its much more precise. The cross section for the {sup 209}Bi({sup 18}O,3n){sup 224}Pa reaction was measured to be 0.5{plus_minus}0.1 mb for 87{endash}89 MeV {sup 18}O{sup 5+} projectiles incident on the target.

We have measured the mass and kinetic-energy distributions of fragments from the spontaneous fission of Lr-259. The Lr-259 was produced via the Cm-248 (N-15,4n) reaction with a production cross section of 100 nb using 81-MeV projectiles. The kinetic energies and times of the alpha particles and coincident fission fragments were measured using our rotating wheel system. From these data the half-life, mass, and kinetic-energy distributions were derived. The total kinetic-energy (TKE) distribution appears to consist of a single component with a most probable pre-neutron-emission TKE of 215+/-3 MeV. The mass distribution is predominantly symmetric with a full width at half maximum of about 20 mass numbers. These results are consistent with trends observed for other trans-berkelium spontaneously fissioning isotopes. We determined the half-life to be 6.14+/-0.36 s by measuring its alpha decay and the observed spontaneous fission half-life was consistent with that value. An energy of 8.439+/-0.010 MeV was measured for the main alpha transition of Lr-259. We measured a spontaneous fission to alpha-decay ratio of 0.25+/-0.03 which results in a partial half-life for spontaneous fission of 31+/-4 s, if there are no other appreciable modes of decay.

The independent yields, recoil properties, and forward-to-backward ratios (F/B) of iodine isotopes from the interaction of 240 MeV $^{12}\mathrm{C}$ with $^{238}\mathrm{U}$ have been measured radiochemically by the thick-target/thick-catcher method. The isotopic yield distribution curve has been constructed and is found to consist of two overlapping Gaussians, peaking at A=126.5 and 133.8 with width parameters of 2.29 and 2.04 mass units, respectively. All the measured iodine isotopes had ranges of 7.7\ifmmode\pm\else\textpm\fi{}0.4 mg/${\mathrm{cm}}^{2}$. The neutron-deficient products have F/B of 1.76\ifmmode\pm\else\textpm\fi{}0.14, but the neutron-excessive products have F/B of only 1.09\ifmmode\pm\else\textpm\fi{}0.06. The yield curve was analyzed with the liquid drop model and the recoil curve was analyzed by the standard two-step vector model; the results show that the neutron-deficient products are formed from nonequilibrium processes and the neutron-excessive products are formed from the normal low-energy fission process.

Production of neutron-rich Bi isotopes was investigated by irradiating Hg, Tl, and Pb targets with $^{18}\mathrm{O}$ ions in the 5-10 MeV/nucleon range. Following irradiation, bismuth was chemically separated and the yields of $^{211\ensuremath{-}213}\mathrm{Bi}$ isotopes were determined via $\ensuremath{\alpha}$-emitting Po daughters. Effective residual transfers of $^{3\ensuremath{-}5}\mathrm{H}$ to $^{208}\mathrm{Pb}$, $^{7,8}\mathrm{He}$ to $^{205}\mathrm{Tl}$, and $^{8}\mathrm{Li}$ to $^{204}\mathrm{Hg}$ were observed. Cross sections generally peaked in the 7-8 MeV/nucleon region and ranged from a high of \ensuremath{\sim}2 mb for $^{3}\mathrm{He}$ absorption to \ensuremath{\sim}0.6 nb for $^{8}\mathrm{He}$ absorption. Total $\ensuremath{\alpha}$- and $\ensuremath{\beta}$-decay branches of the ${J}^{\ensuremath{\pi}}={9}^{\ensuremath{-}},25$ min isomer of $^{212}\mathrm{Bi}$ were measured to be 67% and 33%, respectively, (3.2\ifmmode\pm\else\textpm\fi{}0.2)% of the decays being associated with $\ensuremath{\beta}$-delayed $\ensuremath{\alpha}$-particle emission. Production yields for the ${J}^{\ensuremath{\pi}}={1}^{\ensuremath{-}}$ ground state and ${9}^{\ensuremath{-}}$ and ${15}^{\ensuremath{-}}$ isomeric levels for $^{212}\mathrm{Bi}$ were extracted. The ratio of isomeric states to the ground state increased by more than two orders of magnitude over the energy range studied. However, the maximum value of the cross section ratio $\frac{\ensuremath{\sigma}({J}^{\ensuremath{\pi}}={15}^{\ensuremath{-}})}{\ensuremath{\sigma}({J}^{\ensuremath{\pi}}={9}^{\ensuremath{-}})}$ was only 0.04, implying a low angular momentum transfer. The reactions were analyzed using the Wilczy\ifmmode \acute{n}\else \'{n}\fi{}ski "sum rule," which gave a rather poor fit to the results with respect to both the yield and the implied angular momentum transfer. The observed relatively high cross sections, modest angular momentum transfer, and broad excitation functions indicate that transfer processes provide a viable method for reaching neutron-rich nuclides in the heavy element region.

Excitation functions have been measured for the production of isotopes of Bk through Fm in bombardments of /sup 248/Cm with 97- to 122-MeV /sup 18/O ions and of isotopes of Bk through No in bombardments of /sup 249/Cf with 91- to 150-MeV /sup 18/O ions. The cross sections and widths of the mass distributions for the actinides produced in these reactions are very similar for transfer of the same numbers of nucleons. A semiquantitative comparison of the experimental results with calculations based on a simple model shows that calculations of this type are helpful in selection of projectile-target systems and optimum energies for production of specific actinide isotopes and for synthesis of as yet unknown heavy isotopes and elements. Comparisons of experimental results with calculations show that, in general, about half of the kinetic energy of the projectile is transferred to the actinide product.