EVIDENCE FOR RELATIVISTIC EFFECTS IN THE CHEMISTRY OF ELEMENT-104

On the basis of thermodynamic extrapolations, the first transactinide element 104 (Rf = rutherfordium(1)) is expected to form volatile tetra chlorides of lower volatility than those of the homologous element Hf. In contrast, relativistic calculations predict a higher volatility of RfCl(4) compared to HfCl4. The nuclides (261)Rf and Hf-165, With iden tical half-lives of 78 s, were simultaneously produced at the U-400 cy clotron of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna, R ussia, by bombarding a mixed Cm-248/Gd-152 target with O-18 ions. With the on-line gas chemistry apparatus (OLGA), the retention behavior of volatile Rf- and Hf-chloride in a quartz chromatography column was in vestigated. The results showed that Rf forms chlorides of higher volat ility than those of Hf, in agreement with relativistic calculations. I n addition, the behavior of element 104 was investigated in chlorinati ng, oxygen containing carrier gas, in order to answer the question whe ther a volatile compound of the form RfOCl(2) exists. The results of o ur experiments give strong evidence for a transport reaction mechanism where RfOCl(2) exists only in the condensed phase and not in the gas phase. (C) 1998 Elsevier Science S.A.