Properties of N=90 Isotones within the Mean Field Perspective

In recent years, the N=90 isotones have been investigated to a large extent in relation to studies of quantum phase transitions. In this paper, we use the mean field approach with pairing-deformation self consistent Total Routhian Surface (TRS) calculations to study the N=90 isotones and neigh- bouring nuclei. The important probes, such as moments of inertia, quadrupole moments, the energy ratio of E(4+1)/E(2+1), octupole and hexadecapole degrees of freedom are considered and the cal- culated results are compared with the available experimental data. From a microscopic point of view, the N=90 isotones characterize the onset of the deformed region and are very well described by mean field calculations. The results are compared with those from other studies in beyond mean-field approximations. Shape coexistence phenomena in the region of interest are discussed.Comment: 7 pages, 10 figure

Structure of proton-rich nuclei via mirror β\beta decay and charge exchange reactions

The β decays of the proton-rich, T z = −2 nuclei 48Fe, 52Ni and 56Zn were investigated by decay spectroscopy at GANIL. The decay schemes were determined, together with absolute Fermi and Gamow-Teller transition strengths. New interesting results were obtained, including the first observation of a new decay mode in the f p-shell, the exotic β- delayed γ-proton decay seen in 56Zn, and the first observation of the 2+ isomer in 52Co. These studies were complemented by Charge Exchange reactions on the stable mirror targets

Beta and gamma decays of J

A β-γ spectroscopy of the J π , 426 keV isomeric state of 24Al (24m Al) has been carried out by using a 24Al secondary beam with high purity and high isomeric ratio. From the absolute γ-ray and β-particle intensities observed in the decay of the isomeric state, the branching ratio R B of the isomeric γ decay from 24m Al to the J π = 4+, ground state of 24Al have been derived. The obtained R B value of 69.6(7)% is much smaller than the previously accepted value of 82.5(30)%. The precise half-life for the isomer decay, T 1/2 m = 130.9(13) ms, has been also determined in this experiment. Accordingly, the M3 γ-decay strength B(M3) of the 24m Al decay becomes smaller and the total β-decay branching ratio becomes larger. In particular, the β-decay branching ratio to the ground state of 24Mg becomes 24.3(9)%, which is 2.4 times larger than the previous value of 10.1(28)%. By combining the branching ratio and the half-life, the Gamow-Teller (GT) transition strength B(GT) of 0.0194(7) is deduced for the GT transition from 24m Al to the J π = 0+, ground state of 24Mg. This value is in good agreement with the values derived from charge-exchange reactions

New Results on Excited States in the one-particle one-hole nucleus Co-56 measured with MINIBALL detectors

The non-yrast states of the odd -odd nucleus Co-56 have been investigated by studying the y-rays induced in the predominantly fusion-evaporation reaction Fe-56(p,n gamma)Co-56 at an incident energy of 10 MeV. The y-rays were measured in-beam with four high-resolution MINIBALL-triple germanium (Ge) detectors. The experiment provided excellent data in gamma-gamma coincidences. The complex level scheme of Co-56 was constructed mainly based on the analysis of these gamma-gamma coincidences. The angular distributions of the gamma-rays were also analysed and allowed us to assign spin-parity values to most of the excited states in this nucleus. Despite the extensive work previously done studying the Co-56 nucleus, the analysis presented in this work has resulted in a large improvement in the knowledge of its structure