Printed in Great Britain. Pergamon Press Ltd. ©1981 IUPAC RECENT SEARCHES FOR SUPERHEAVY ELEMENTS IN DEEP-INELASTIC REACTIONS

Abstract- New attempts have been made to synthesize superheavy elements (SHE) by nuclear reactions that may possibly form the products at low excitation energies. Survival of the superheavy elements would then be enhanced because of reduced losses from prompt fission. Classical and diffusion model calculations of deep-inelastic reactions indicate there should be detectable yields of SHE formed with less than 30 MeV of excitation energy. Acçrdingly, uperheavy elements have been sought in ch reactions where targets of 8Cm and 28U have been irradiated with 136Xe and '8U ions. In the most recent experiments, targets of 248Cm metal (3.5-7 mg-cm-2) were bombarded with l.8-GeV 238U ions from the UNILAC accelerator. The longer-lived SHEs and actinides near the target Z were chemically separated and the yields of a number of isotopes of Bk, Cf, Es, and Fm were measured. An upper limit of 30 nb was obtained for the formation of 1-h 259No. In addition, to the off-line chemical recovery and search for SHE's, we performed an on-line experiment to detect volatile SHE's with half lives of a minute or more. All experiments to produce and detect superheavy elements were much less than optimu