Chemical isolation of dubnium (element 105) in fluoride media

摘要

The isotope (262)Db was produced by irradiation of a Cm-248 target with 106-MeV F-19 ions at the 15 MV NIP Tandem accelerator of Orsay (France). The reaction products were continuously and rapidly transported with a KC1 aerosol helium jet system to the chemistry setup. They were dissolved in HF medium and the solution was passed through three successive ion exchange columns, allowing a continuous high level purification of Db from actinides on a first cation exchange column, the isolation of Db on an anion exchange one, and the retention of the long-lived decay products of (262)Db (3.24 h-(254) Fm) on a second cation exchange column. Just after the end of irradiation, the decay products were desorbed from this column, purified and a-sources were prepared on carbon foil by electrospray. In 13 effective irradiation hours, 22 events corresponding to the alpha-decay of Fm-254 were recorded. Almost 70 atoms of (262)Db, produced in the reaction Cm-248 + F-19 were isolated in dilute HF medium. Like its homologues/analogues Nb, Ta and Pa, dubnium forms, with fluoride ions, negatively charged complexes which are strongly retained on anion exchanger. [References: 33]