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In an experiment at the SISSI/LISE3 facility of GANIL, we have studied the decay of the two proton-rich nuclei 45 Fe and 48 Ni. We identified 30 implantations of 45 Fe and observed for the second time four implantation events of 48 Ni. In 17 cases, 45 Fe decays by two-proton emission with a decay energy of 1.154(16) MeV and a half-life of T 1/2 = 1.6 +0.5 −0.3 ms. The observation of 48 Ni and of its decay allows us to deduce a half-life of T 1/2 = 2.1 +2.1 −0.7 ms. One out of four decay events is completely compatible with two-proton radioactivity and may therefore indicate that 48 Ni has a two-proton radioactivity branch. We discuss all information now available on two-proton radioactivity for 45 Fe and 48 Ni and compare it to theoretical models.

We report on the g-factor measurement of the first isomeric state in (16)43S27 [Ex=320.5(5) keV, T1/2=415(5) ns, and g=0.317(4)]. The 7/2- spin-parity of the isomer and the intruder nature of the ground state of the nucleus are experimentally established for the first time, providing direct and unambiguous evidence of the collapse of the N=28 shell closure in neutron-rich nuclei. The shell model, beyond the mean-field and semiempirical calculations, provides a very consistent description of this nucleus showing that a well deformed prolate and quasispherical states coexist at low energy.

A new isomeric 0(+) state was identified as the first excited state in the self-conjugate (N=Z) nucleus 72Kr. By combining for the first time conversion-electron and gamma-ray spectroscopy with the production of metastable states in high-energy fragmentation, the electric-monopole decay of the new isomer to the ground state was established. The new 0(+) state is understood as the band head of the known prolate rotational structure, which strongly supports the interpretation that 72Kr is one of the rare nuclei having an oblate-deformed ground state. This observation gives in fact the first evidence for a shape isomer in a N=Z nucleus.

Energies and spectroscopic factors of the first 7=2 − , 3=2 − , 1=2 − , and 5=2 − states in the 35 Si 21 nucleus were determined by means of the (d, p) transfer reaction in inverse kinematics at GANIL using the MUST2 and EXOGAM detectors. By comparing the spectroscopic information on the 35 Si and 37 S isotones, a reduction of the p 3=2 -p 1=2 spin-orbit splitting by about 25% is proposed, while the f 7=2 -f 5=2 spin-orbit splitting seems to remain constant. These features, derived after having unfolded nuclear correlations using shell model calculations, have been attributed to the properties of the two-body spin-orbit interaction, the amplitude of which is derived for the first time in an atomic nucleus. The present results, remarkably well reproduced by using several realistic nucleon-nucleon forces, provide a unique touchstone for the modeling of the spin-orbit interaction in atomic nuclei. Introduction.-The spin-orbit (SO) interaction, which originates from the coupling of a particle spin with its orbital motion, plays an essential role in quantum physics. In atomic physics it causes shifts in electron energy levels due to the interaction between their spin and the magnetic field generated by their motion around the nucleus. In the field of spintronics, spin-orbit effects for electrons in materials [1] are used for several remarkable technological applications. In atomic nuclei, the amplitude of the SO interaction is very large, typically of the order of the mean binding energy of a nucleon. It is an intrinsic property of the nuclear force that must be taken into account for their quantitative description.An empirical one-body SO force was introduced in atomic nuclei in 1949 [2] to account for the magic numbers and shell gaps that could not be explained otherwise at that time. In this framework each nucleon experiences a coupling between its orbital momentum l⃗ and intrinsic spin ⃗ s. This ls coupling is attractive for nucleons having their orbital angular momentum aligned with respect to

174Yb(3He,αγ )173Yb* and 174Yb(3He,pγ )176Lu*, respectively. For the first time, the gamma-decay probabilities have been obtained with two independent experimental methods based on the use of C6D6 scintillators and Germanium detectors. Our results for the radiative-capture cross sections are several times higher than the corresponding neutron-induced data. To explain these differences, we have used our gamma-decay probabilities to extract rather direct information on the spin distributions populated in the transfer reactions used. They are about two times wider and the mean values are 3 to 4 ¯h higher than the ones populated in the neutron-induced reactions. As a consequence, in the transfer reactions neutron emission to the ground and first excited states of the residual nucleus is strongly suppressed and gamma-decay is considerably enhanced

The half-lives of 20 neutron-rich nuclei with Z ¼ 27-30 have been measured at the RIBF, Atomic nuclei are quantum many-body systems consisting of two distinct types of fermions-protons and neutrons. Analogous to atomic physics, the concept of nuclear shell structure was triggered by the discovery of particularly stable nuclei with specific numbers of proton and neutron, such as 2, 8,20,28, 50, 82, and 126 along the β-stability line [1]. By assuming a strong spin-orbit interaction within a mean field potential, these magic numbers were correctly interpreted and regarded to be immutable throughout the nuclear chart [2,3]. However, with the development of experimental techniques exploiting radioactive ion beams, many nuclei with extreme neutron-to-proton ratios (N=Z), so-called exotic nuclei, have been produced and studied in the last few decades. The results obtained heretofore have demonstrated that the shell structure established for nuclei near the β-stability line may change drastically in these exotic nuclei. For instance, classical magic numbers in 12 Be (N ¼ 8), 32 Mg (N ¼ 20), and 42 Si (N ¼ 28) were found to disappear [4-6], whereas new magic numbers emerged in 24 O (N ¼ 16) and 54 Ca (N ¼ 34) [7][8][9]. To address the origins of shell evolution in heavier mass regions, it is of particular interest to investigate the properties of nuclei in the vicinity of 78 Ni, which has the proton number Z ¼ 28 and the neutron number N ¼ 50 with a large neutron excess N=Z ≈ 1.8.To study the shell evolution around 78 Ni, many experimental efforts have been made. One of the interesting phenomena related to the proton Z ¼ 28 shell gap is the monopole migration in Cu isotopes. A sudden drop of the excited 5=2− state relative to the ground 3=2 − state was observed in 71;73 Cu [10,11]. These two states are characterized by a single-particle nature [12] and their order was