0000000001035312
AUTHOR
K. J. Moody
New nuclides: Neptunium-243 and neptunium-244
We have observedγ-rays following the β−-decay of243Np and244Np after chemical isolation of neptunium isotopes from the products of the reaction of 835 MeV136Xe with244Pu. The ground-state of 1.85-min243Np hasJ=5/2. The decay of 2.29-min244Np (probableJπ=7−) populates high-spin members of the ground state rotational band in244Pu.
Continuous separation and identification of neutronrich neptunium isotopes from heavy-ion reactions by means of the centrifuge system “sisak”
Abstract Neutron-rich neptunium isotopes formed in direct transfer reactions between 136 Xe projectiles and targets of 244 Pu have been separated from other reaction products with the on-line liquid-liquid extraction system SISAK. A four-detector delay method was used to determine the half-lives of the previously unknown isotopes 243 Np and 244 Np. From the decay of the 287.4 keV γ-line a half-life of 1.8 ± 0.3 min was determined for 243 Np. From the decay curves of the γ-lines at 162.7 and 216.7 keV, which fit into the known level scheme of 244 Pu, a half-life of 2.5 ± 0.3 min results for 244 Np.
On the adsorption and reactivity of element 114, flerovium
Flerovium (Fl, element 114) is the heaviest element chemically studied so far. To date, its interaction with gold was investigated in two gas-solid chromatography experiments, which reported two different types of interaction, however, each based on the level of a few registered atoms only. Whereas noble-gas-like properties were suggested from the first experiment, the second one pointed at a volatile-metal-like character. Here, we present further experimental data on adsorption studies of Fl on silicon oxide and gold surfaces, accounting for the inhomogeneous nature of the surface, as it was used in the experiment and analyzed as part of the reported studies. We confirm that Fl is highly v…
Reactions of40Ar with233U,235U, and238U at the barrier
Production cross sections for target-like transfer products in reactions of40Ar with233,235,238U at the barrier were determined using radiochemical techniques. The heaviest products detected are isotopes of californium (Z=98). In addition to the quasi-elastic component of the isotopic distributions observed in the vicinity of uranium, there are also relaxed contributions throughout the entire region. The peak positions of the isotope distributions of this component for fixed atomic number, after the transfer of > 3 charges, approach closely the minimum of the potential energy surfaces (PES). The experimental results thus indicate the cold formation of the reaction products. A search for lon…
Population of nuclides with Z≥98 in multi-nucleon transfer reactions of 48Ca + 248Cm
The results for nuclei above curium, produced in multi-nucleon transfer reactions of 48Ca + 248Cm at the velocity filter SHIP of GSI Darmstadt, are presented. Spontaneous fission and α-activities have been used to study the population of nuclei with lifetimes ranging from few milliseconds to several days. We observed several, relatively neutron-rich isotopes with atomic numbers Z≥98; among them a weak 224 millisecond activity which we tentatively attributed to 260No. The measured cross-sections of the observed nuclei give hope that multi-nucleon transfer reactions are a way to reach new neutron-rich heavy and superheavy nuclei, which are not accessible in other reactions. We compare our res…
Attempts to Produce Superheavy Elements by Fusion ofCa48withCm248in the Bombarding Energy Range of 4.5-5.2 MeV/u
A search for superheavy elements was made in bombardments of $^{248}\mathrm{Cm}$ with $^{48}\mathrm{Ca}$ ions performed at projectile energies close to the interaction barrier in order to keep the excitation energy of the compound nucleus $Z=116$, $A=296$ as low as possible. No evidence for superheavy nuclei was obtained in a half-life region from 1 \ensuremath{\mu}s to 10 yr with a production cross section greater than ${10}^{\ensuremath{-}34}$ to ${10}^{\ensuremath{-}35}$ ${\mathrm{cm}}^{2}$.