Preprint / Chemical Physics and Chemistry E122004157 JINRE122004157

Results of the Experiment on Chemical Identification of Db as a Decay Product of Element 115

Dmitriev, S N ; Oganessian, Yu T ; Utyonkov, V K ; Shishkin, S V ; Eremin, A V ; Lobanov, Yu V ; Tsyganov, Yu S ; Chepigin, V I ; Sokol, E A ; Vostokin, G K ; Aksenov, N V ; Hussonnois, M ; Itkis, M G ; Aggeler, H W ; Schumann, D ; Bruchertseifer, H ; Eichler, R ; Shaughnessy, D A ; Wilk, P A ; Kenneally, J M ; Stoyer, M A ; Wild, J F

Pages: 10 p
Year: 2004

Abstract: For the first time the chemical identification of Db as the terminal isotope of the decay element 115 produced via the $^{243}{\text{Am}}(^{48}{\text{Ca}},3n)^{288}115$ reaction was realized. The experiment was performed on the U400 cyclotron of FLNR, JINR. The $^{243}$Am target was bombarded with a beam dose of $3.4\cdot 10^{18}$ $^{48}$Ca projectiles at an energy of 247 MeV in the center of the target. The reaction products were collected in the surface of a copper catcher block, which was removed with a lathe and then dissolved in concentrated HNO$_3$. The group 5 elements were separated by sorption onto Dowex 50$\times$8 cationexchange resin with subsequent desorption using 1M HF, which forms anionic fluoride complexes of group 5 elements. The eluant was evaporated onto 0.4 $\mu$m thick polyethylene foils which were placed between a pair of semiconductor detectors surrounded by $^3$He neutron counters for measurement of $\alpha$ particles, fission fragments and neutrons. Over the course of the experiment, we observed 15 spontaneous fission events with $T_{1/2}=32^{+11}_{7}$ h which we attribute to $^{268}$Db. The production cross section for the $^{243}{\text{Am}}+{}^{48}{\text{Ca}}$ reaction was $4.2^{+1.6}_{1.2}$ pb. These results agree with the original element 115 synthesis experiment where $^{268}$Db was first observed as the terminal isotope following the five consecutive $\alpha$ decays from the $^{288}$115 parent nucleus at the Dubna gasfilled separator. The data from the present experiment give independent evidence fot the synthesis of element 115 as well as element 113 via the $^{243}{\text{Am}}+{}^{48}{\text{Ca}}$ reaction.

Language: eng

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