The results of a study of the beta decays of three proton-rich nuclei with Tz = -2, namely 48 Fe, 52 Ni and 56 Zn, produced in an experiment carried out at GANIL, are reported. In all three cases we have extracted the half-lives and the total β-delayed proton emission branching ratios. We have measured the individual β-delayed protons and β-delayed γ rays and the branching ratios of the corresponding levels. Decay schemes have been determined for the three nuclei, and new energy levels are identified in the daughter nuclei. Competition between β-delayed protons and γ rays is observed in the de-excitation of the T = 2 Isobaric Analogue States in all three cases. Absolute Fermi and Gamow-Teller transition strengths have been determined. The mass excesses of the nuclei under study have been deduced. In addition, we discuss in detail the data analysis taking as a test case 56 Zn, where the exotic β-delayed γ-proton decay has been observed.

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.

Context. Under cosmic irradiation, the interstellar water ice mantles evolve towards a compact amorphous state. Crystalline ice amorphisation was previously monitored mainly in the keV to hundreds of keV ion energies. Aims. We experimentally investigate heavy ion irradiation amorphisation of crystalline ice, at high energies closer to true cosmic rays, and explore the water-ice sputtering yield. Methods. We irradiated thin crystalline ice films with MeV to GeV swift ion beams, produced at the GANIL accelerator. The ice infrared spectral evolution as a function of fluence is monitored with in-situ infrared spectroscopy (induced amorphisation of the initial crystalline state into a compact amorphous phase). Results. The crystalline ice amorphisation cross-section is measured in the high electronic stopping-power range for different temperatures. At large fluence, the ice sputtering is measured on the infrared spectra, and the fitted sputtering-yield dependence, combined with previous measurements, is quadratic over three decades of electronic stopping power. Conclusions. The final state of cosmic ray irradiation for porous amorphous and crystalline ice, as monitored by infrared spectroscopy, is the same, but with a large difference in cross-section, hence in time scale in an astrophysical context. The cosmic ray water-ice sputtering rates compete with the UV photodesorption yields reported in the literature. The prevalence of direct cosmic ray sputtering over cosmic-ray induced photons photodesorption may be particularly true for ices strongly bonded to the ice mantles surfaces, such as hydrogen-bonded ice structures or more generally the so-called polar ices.

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The unbound nucleus 18 Na, the intermediate nucleus in the two-proton radioactivity of 19 Mg, was studied by the measurement of the resonant elastic scattering reaction 17 Ne(p, 17 Ne)p performed at 4 A.MeV. Spectroscopic properties of the low-lying states were obtained in a R-matrix analysis of the excitation function. Using these new results, we show that the lifetime of the 19 Mg radioactivity can be understood assuming a sequential emission of two protons via low energy tails of 18 Na resonances. From near to beyond the drip-lines, the nuclear force is no longer able to bind the interacting nucleons leading to instability of nuclei with respect to nucleon emission. On the proton-rich side of the chart of nuclides, the pairing force may lead to a situation where a drip-line nucleus is bound with respect to single proton emission but unbound to two-proton emission [1,2]. Several types of two-proton emitters have been observed. On the one hand, there are the short-lived (τ 1/2 ≤ 10 −18 s) light nuclei such as 6 [6] when assuming only d-wave single-particle states in the low-lying structure of 18 Na and thus a dominant d 2 single-particle configuration for 19 Mg. Theoretical calculations of properties of 19 Mg depend strongly on the assumption made about the structure of 18 Na and its mirror nucleus. In this letter, we investigate both experimentally and theoretically the low lying spectrum of 18 Na. We strongly refine the knowledge about the lowlying spectrum of 18 Na and find that there are also lowlying s-wave states. These states should strongly boost the expected two-proton width.On the theoretical side, the structure of 18 Na has been predicted assuming a core of 17 Ne + proton structure [6] or by coupling a neutron hole to the lowest states in 19 Na [7]. In both cases, the low-lying structure of 18 Na is found to have d-wave configuration. In the following, another theoretical approach is described and predicts also low lying s-wave states. The dimensionless reduced widths θ 2 (sometimes called spectroscopic factors) where estimated with the shell model. The values shown in Tab. I were obtained with the OXBASH code [8] and the ZBM interaction [9] in the 1p 1/2 , 1d 5/2 and 2s 1/2 shells space. It predicts that the first six low lying states can be described mainly (with θ 2 > 0.5) by single particle con-