New Element Hahnium, Atomic Number 105

Abstract

An isotope of element 105 with mass number 260 has been formed by bombarding ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$ with ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ ions. The $Z$ and $A$ of the nuclide have been unambiguously identified by recoilmilking the 30-second ${}_{}{}^{256}{}_{}{}^{}\mathrm{Lr}$ daughter. ${}_{}{}^{260}{}_{}{}^{}105$ has a (1.6±0.3)-sec half-life and decays by alpha-particle emission with groups at 9.06 (55%), 9.10 (25%), and 9.14 MeV (20%). Branching decay by spontaneous fission is less than 20%. Some comments are made on the earlier results of the Dubna group concerning a few alpha-particle events at 9.4 and 9.7 MeV which they claim to be due to element 105.