Production of Db 262 in the Cm 248 (F 19,5 n) Db 262 reaction and decay properties of Db 262 and Lr 258

The nuclide Db262 was produced in the Cm248(F19,5n)Db262 reaction at beam energies of 103.1 and 97.4 MeV. Decay properties of Db262 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 76 chains were assigned to Db262 and its α-decay daughter nuclide Lr258. No correlated decay chain was observed for ²⁶³Db produced in the Cm248(F19,4n)²⁶³Db reaction and its daughter ²⁵⁹Lr. The half-lives of Db262 and Lr258 were measured to be T12=33.8-3.5+4.4 and 3.54-0.36+0.46s, respectively, and they confirmed the literature data. The α-particle energy (Eα) and intensity (Iα) of Db262 were revised to Eα = 8.46 ± 0.04 MeV (Iα = 70 ± 5%) and Eα = 8.68 ± 0.03 MeV (Iα = 30 ± 5%). The SF activity with T1/2 = 30.2 ± 6.1 s was assigned to Db262, and the SF branch of Db262 was determined to be bSF = 52 ± 4%. From an observation of two SF decays which correlated to the α decay of Db262, an electron capture (EC) decay with bEC = 2.6 ± 1.8% was suggested in Lr258. The production cross sections for the Cm248(F19,5n)Db262 reaction were determined to be 2.1 ± 0.7 nb at 103.1 MeV and 0.23-0.11+0.18nb at 97.4 MeV, whereas, those for the Cm248(F19,4n)²⁶³Db reaction were the upper limits of ≤0.064 nb at 103.1 MeV and ≤0.13 nb at 97.4 MeV. These cross sections are discussed by comparing with the literature data as well as the theoretical prediction.