J. Giovinazzo

First observation of 54Zn and its decay by two-proton emission

The nucleus 54Zn has been observed for the first time in an experiment at the SISSI/LISE3 facility of GANIL in the quasifragmentation of a 58Ni beam at 74.5 MeV/nucleon in a (nat)Ni target. The fragments were analyzed by means of the ALPHA-LISE3 separator and implanted in a silicon-strip detector where correlations in space and time between implantation and subsequent decay events allowed us to generate almost background free decay spectra for about 25 different nuclei at the same time. Eight 54Zn implantation events were observed. From the correlated decay events, the half-life of 54Zn is determined to be 3.2(+1.8)(-0.8) ms. Seven of the eight implantations are followed by two-proton emission with a decay energy of 1.48(2) MeV. The decay energy and the partial half-life are compared to model predictions and allow for a test of these two-proton decay models.

Isomer spectroscopy of neutron rich 190W116

Abstract Gamma-rays de-exciting a millisecond isomer in the neutron-rich nucleus 190 74 W 116 have been observed following relativistic projectile fragmentation of a 1xa0GeV per nucleon 208 Pb beam. The isomeric decay populates the ground-state rotational band, with energies that indicate a significant deformation change at Z =74 for the N =116 isotones. The successful application of the projectile fragmentation technique in a region of deformed nuclei opens up the prospect of exploiting K -isomer decays to probe the evolution of collective nuclear structure far from the valley of beta stability.

The delayed proton emission in the A≃65–77 mass region, statistical aspects and structure effects

Abstract In the decay of the series of T Z =1/2 nuclei, 65 Ge, 69 Se, 73 Kr and 77 Sr, a statistical analysis was applied to the β delayed proton emission to obtain nuclear structure information. New results emerge from this study, in the light of improvements in the experimental techniques and developments of the analysis method. Experimental results are analysed by comparison with a statistical model, in order to extract information on level densities and partial transition widths of the proton emitting nuclei. Limitations of the existing descriptions of processes for nuclei far from stability are pointed out.

Deformation signature from the Gamow-Teller decay of N=Z nuclei

The 76Sr (N=Z=38) and the 72Kr (N=Z=36) β+ EC decay have been studied at the CERN/ISOLDE PSB facility where their beta-gamma and delayed particle decay modes have been investigated. The established decay schemes yield new information on the Gamow-Teller (GT) strength spread over the Jπ=1+ states in the daughter nuclei. The delayed proton emission of an N=Z nucleus is observed for the first time in the case of 76Sr. The experimental GT strength intensities and distributions are discussed in the light of the theoretical estimates for oblate and prolate deformations.

Half-Lives of the Odd-Odd N = Z Nuclei

The heavy odd-odd nuclei , , , have been produced at GANIL by fragmentation of a beam on a natural nickel target. The species of interest were selected and identified by their energy loss in a silicon detector and their time of flight through the LISE spectrometer. The ions were implanted in a silicon strip detector in which their -decay was observed. The measured half-lives for , , correspond to superallowed transitions and may sign Fermi transitions on the basis of values. Our experimental results pave the way for further and more precise measurements of these nuclei.

^78

The heavy odd-odd N=Z nuclei {sup 78}Y,{sup 82}Nb,{sup 86}Tc have been produced at GANIL by fragmentation of a 60 MeV/u {sup 92}Mo beam on a natural nickel target. Their lifetime have been measured for the first time, using the identification-implantation and subsequent time correlated {beta} counting technique at the LISE spectrometer. The obtained half-lives for {sup 78}Y,{sup 82}Nb,{sup 86}Tc are consistent with the microscopic predictions. These nuclei are good candidates to extend the mass range for the V{sub ud} matrix element evaluation and our experimental results highlight the interest of further investigation of their excited states and {beta} decay schemes as a function of isospin. {copyright} {ital 1998 American Institute of Physics.}