Dubnium is a chemical element in the periodic table that has the symbol Db and atomic number 105.
“In 1968 experiments were conducted at the Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research in order to produce a new chemical element with atomic number 105 . In the case of the irradiation of Am243 with accelerated Ne22 ions with a very small cross section, the formation of short-lived emitters of α – particles with an energy of 9.4-9.7 MeV was observed.
However, on the basis of an analysis of the decay schemes of the known α-radioactive nuclei with an odd number of nucleons, it may be assumed that the bulk of the α-decay of the isotopes with Z = 105 corresponds to the excited levels of the daughter nuclei (Z = 103), and the most intense α-lines belonging to the isotopes 105260 and 105261 should be sought in the softer part of the α-spectrum (Eα-< 9.1 MeV). Unfortunately, the energy interval 8.8-9.0 MeV includes the α – particles of isotopes (Z < 92) formed as a result of nuclear reactions on trace impurities of lead in the americium target . Therefore, despite extensive work on the purification of the target from lead, the analysis of this part of the spectrum was greatly hindered in .
Nonetheless, the synthesis of element 105 can also be approached from the other side…”
From “THE SYNTHESIS OF ELEMENT 105”. G.N.Flerov, Yu.Ts.Oganessian, Yu.V.Lobanov, Yu.A.Lazarev, S.P.Tret’yakova, I.V.Kolesov, and V.M.Plotko download: [ pdf ] (767Kb)
Dmitriev S.N. et al. Results of the Experiment on Chemical Identification of Db as a Decay Product of Element 115 Preprint of the JINR. Dubna, 2003.
download: [ pdf ] (347Kb)