An isotope of the 113th element, i.e., 278 113, was produced in a nuclear reaction with a 70 Zn beam on a 209 Bi target. We observed six consecutive decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector under an extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of 262 Db and 258 Lr in both decay energies and decay times. This indicates that the present decay chain consisted of 278 113, 274 Rg (Z 111), 270 Mt (Z 109), 266 Bh (Z 107), 262 Db (Z 105), and 258 Lr (Z 103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads to the unambiguous production and identification of the isotope 278 113 of the 113th element.
The projectile fragmentation reactions of 40 Ar at 57 MeV/nucleon on 9 Be and 181 Ta targets have been studied by the Radioactive Ion Beam Line in Lanzhou (RIBLL) at the Heavy-Ion Research Facility in Lanzhou (HIRFL). The momentum distributions of fragments have been measured and the competition between different mechanisms are observed. The production cross sections have been obtained and compared with the empirical parametrization of fragmentation cross section (EPAX), abrasion-ablation (AA), and heavy-ion phase space exploration (HIPSE) models, and the target dependence of fragment cross sections has also been discussed.
Excited states have been observed for the first time in the neutron-deficient nucleus 117 Ba using the Recoil-Decay Tagging technique following the heavy-ion fusion-evaporation reaction 64 Zn( 58 Ni, 2p3n)117 Ba. Prompt γ rays have been assigned to 117 Ba through correlations with β-delayed protons following the decay of A = 117 recoils. Through the analysis of the γ-γ coincidence relationships, a high-spin level scheme consisting of two bands has been established in 117 Ba. Based on the systematics of the level spacings in the neighboring barium isotopes, the two bands are proposed to have νh 11/2 [532]5/2 − and νd 5/2 [413]5/2 + configurations, respectively. The observed band-crossing properties are interpreted in the framework of cranked shell model.
With the recent commissioning of a gas-filled recoil separator at Institute of Modern Physics (IMP) in Lanzhou, the decay properties of 271Ds (Z = 110) were studied via the 208Pb(64Ni, n) reaction at a beam energy of 313.3 MeV. Based on the separator coupled with a position sensitive silicon strip detector, we carried out the energy-position-time correlation measurements for the implanted nucleus and its subsequent decay α's. One α-decay chain for 271Ds was established. The α energy and decay time of the 271Ds nucleus were measured to be 10.644 MeV and 96.8 ms, which are consistent with the values reported in the literature.
The complete fusion reaction 40 Ca+ 175 Lu was studied at a beam energy of 5.1 MeV u −1 . Evaporation residues recoiled from the target were separated from the primary beam by the gas-filled recoil separator SHANS and then implanted into the focal plane detection system. Based on the energy-positiontime correlation measurement, neutron-deficient nuclei − 208 213 Ac, 212 Pa and 211 Th produced in this reaction were identified. Previously reported decay properties of the ground state in 212 Pa were confirmed and improved values of − + 5.1 1.75.1 ms and 8.250(20) MeV for the half-life and α-particle energy of 212 Pa were obtained. No correlated decay chain arising from 211 Pa was observed and an upper limit for the cross section of 211 Pa was estimated.
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