Production of 266Bh in the 248Cm(23Na,5 n )266Bh reaction and its decay properties

The nuclide ²⁶⁶Bh was produced in the ²⁴⁸Cm(²³Na,5 n )²⁶⁶Bh reaction at beam energies of 125.9, 130.6, and 135.3 MeV. Decay properties of ²⁶⁶Bh were investigated with a rotating wheel apparatus for α and spontaneous fission (SF) spectrometry under low background conditions attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. Based on genetically correlated α -α and α -SF decay chains, a total of 23 chains were assigned to ²⁶⁶Bh and its daughter nuclide ²⁶²Db and granddaughter ²⁵⁸Lr. The half-life of ²⁶⁶Bh was measured to be T_1/2=10.0_-1.7^+2.6s which is an order of magnitude longer than the literature data. The α -particle energies of ²⁶⁶Bh disperse widely in the range of E_α=8.62 -9.40 MeV . The maximum production cross section for the ²⁴⁸Cm(²³Na,5 n )²⁶⁶Bh reaction was determined to be σ =57 ±14 pb at 130.6 MeV, whereas the upper limit for the ²⁴⁸Cm(²³Na,4 n )²⁶⁷Bh reaction was σ ≤14 pb at 121.2 MeV. These cross sections are discussed by comparing with the literature data as well as the theoretical calculations.