A new alpha-particle-emitting isotope 259Db

An isotope of the element 105 with mass number 259 has been produced via the reaction 241Am(22Ne,4n)259Db at Elab=118 MeV. The reaction products were transported and collected using the helium-jet technique and the rotating wheel apparatus. The α-decays of the products and their daughter nuclides were detected by a set of Si(Au) detectors arranged ingeniously. The Z and A of the nuclide have been unambiguously identified by the genetic relationship between the new activity and the known nuclide 255Lr established by α-recoiled milking measurement. The new nuclide 259Db has a half-life of 0.51±0.16 s and decays by alpha-particle emission of Eα=9.47 MeV. Furthermore, the nuclide 258Db and its daughter 254Lr have also been clearly observed using the same projectile-target combination. Their half-lives and α-particle energies determined in this work are in agreement with previous known data, thus also proving the reliability of our assignment of 259Db. (orig.)