Gamma-ray fast-timing coincidence measurements from the 18O+18O fusion-evaporation reaction using a mixed LaBr3-HPGe array.
We report on a gamma-ray coincidence analysis using a mixed array of hyperpure germanium and cerium-doped lanthanum tri-bromide (LaBr3:Ce) scintillation detectors to study nuclear electromagnetic transition rates in the pico-to-nanosecond time regime in 33,34P and 33S following fusion-evaporation reactions between an 18O beam and an isotopically enriched 18O implanted tantalum target. Energies from decay gamma-rays associated with the reaction residues were measured in event-by-event coincidence mode, with the measured time difference information between the pairs of gamma-rays in each event also recorded using the ultra-fast coincidence timing technique. The experiment used the good full-energy peak resolution of the LaBr3:Ce detectors coupled with their excellent timing responses in order to determine the excited state lifetime associated with the lowest lying, cross-shell, Iπ=4- "intruder" state previously reported in the N=19 isotone 34P. The extracted lifetime is consistent with a mainly single-particle M2 multipolarity associated with a f7/2→d5/2 single particle transition.
Relativistic mean field study of ``island of inversion'' in neutron-rich Ne, Na, Mg nuclei
Abstract The relativistic mean field model of interacting nucleons and mesons is used to study the structure of neutron-rich Ne, Na, Mg nuclei using a deformed basis. Results for binding energies are remarkably close to experimental values, thus addressing the problem of “island of inversion”. The spins of 29,31Na are correctly predicted as 3 2 + .
Binding energy of the sd shell nuclei in the supersymmetric model
The supersymmetric model within the interacting boson model IBM4 with spin and isospin quantum numbers has been applied in our previous papers to the interpretation of energy levels and electromagnetic E2 transitions. The application of the model supersymmetric Hamiltonian to the binding energy calculations leads to the approximate mass formula with a relatively small number of parameters. The results when compared with experimental data are quite satisfactory, although not so good as extended shell model results. There is, however, another aim of this paper, namely to present an additional argument for the main assumption: the supersymmetry of the sd shell nuclei.