The production cross sections for the actinides from ' Xe bombardments of Cf at energies 1.02, 1.09, and 1.16 times the Coulomb barrier were determined. Chemical fractions of the individual actinide elements were prepared and the gamma, alpha, and spontaneous fission activities of the actinide isotopes were measured. The cross section distributions are presented and compared with those from other heavy ion bombardments of actinide targets. Conclusions are drawn as to the utility of these heavy ion bombardments for producing unknown isotopes in the actinide region. It is shown that for new neutron-rich actinide isotopes with atomic numbers smaller than that of the target these very heavy ion bombardments are perhaps the best method of production, and when using the most neutron-rich targets available new neutron-rich isotopes should be produced in quantities sufficient for their identification and study.
A search for superheavy elements was made in bombardments of 248 Cm with 48 Ca ions performed at projectile energies close to the interaction barrier in order to keep the excitation energy of the compound nucleus Z = 116, A = 296 as low as possible. No evidence for superheavy nuclei was obtained in a half-life region from 1 JJLS to 10 yr with a production cross section greater than 10-34 tol0-35 cm 2 .
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