B. Blank

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.

Observation of the β-delayed γ-proton decay of (56)Zn and its impact on the Gamow-Teller strength evaluation.

We report the observation of a very exotic decay mode at the proton drip line, the β-delayed γ-proton decay, clearly seen in the β decay of the T_{z}=-2 nucleus ^{56}Zn. Three γ-proton sequences have been observed after the β decay. Here this decay mode, already observed in the sd shell, is seen for the first time in the fp shell. Both γ and proton decays have been taken into account in the estimation of the Fermi and Gamow-Teller strengths. Evidence for fragmentation of the Fermi strength due to strong isospin mixing is found.

Beta-decay branching ratios of 62Ga

Abstract.Beta-decay branching ratios of 62Ga have been measured at the IGISOL facility of the Accelerator Laboratory of the University of Jyväskylä. 62Ga is one of the heavier Tz = 0 , 0+ → 0+ β -emitting nuclides used to determine the vector coupling constant of the weak interaction and the Vud quark-mixing matrix element. For part of the experimental studies presented here, the JYFLTRAP facility has been employed to prepare isotopically pure beams of 62Ga . The branching ratio obtained, BR = 99.893(24) %, for the super-allowed branch is in agreement with previous measurements and allows to determine the ft value and the universal Ft value for the super-allowed β -decay of 62Ga .

The Mass Programme at GANIL Using the CSS2 and CIME Cyclotrons

The mass-measurement programme at GANIL aims to measure the masses of heavy nuclei close to the N=Z line which is the ideal region to study neutron-proton pairing. An original direct time-of-flight mass-measurement method was developed at GANIL which uses the CSS2 cyclotron as a high-resolution spectrometer. The masses of ions of A=68,76,80 and 100 have been measured with a precision of a few 10−6. Mass measurements will be performed with the new CIME cyclotron of SPIRAL using a similar method based on the measurement of the phase of the accelerated ions for different radio-frequencies. A recently approved experiment will help develop this new technique and aims to measure the mass of 31Ar radioactive nuclei with a precision of 10−6.

Mass Measurements with the CSS2 and CIME cyclotrons at GANIL

This paper presents two original direct mass‐measurement techniques developed at GANIL using the CSS2 and CIME cyclotrons as high‐resolution mass spectrometers. The mass measurement with the CSS2 cyclotron is based on a time‐of‐flight method along the spiral trajectory of the ions inside the cyclotron. The atomic mass excesses of 68Se and 80Y recently measured with this technique are −53.958(246) MeV and −60.971(180) MeV, respectively. The new mass‐measurement technique with the CIME cyclotron is based on the sweep of the acceleration radio‐frequency of the cyclotron. Tests with stable beams have been performed in order to study the accuracy of this new mass‐measurement method and to understand the systematic errors.

Excitation of the isovector giant quadrupole resonance in 208Pb by Coulomb inelastic scattering

Excitation of the Isovector Giant Quadrupole Resonance in 208Pb by Coulomb Inelastic Scattering R. L. Varner, J. R. Beene, M. Chartier, ∗ J. F. Liang, D. Shapira, D. Bazin, B. Blank, ∗ B. Sherrill, M. Thoennessen, P. A. DeYoung, and G. F. Peaslee Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6368 National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824

First observation of doubly-magic 48Ni

The doubly magic nucleus 48Ni has been observed for the first time at GANIL. The experiment was performed using a high intensity 58Ni beam at 74.5 MeV/A on a nickel target. This TZ=−4 nucleus is the most proton-rich nucleus ever observed, and is a good candidate for two-proton radioactivity. In this experiment, we also implanted around 28042Cr, 5043Fe and 10049Ni isotopes, for which no experimental information about the decay is available.