[en] Nature uses radioactivity to gain stability for an unstable atomic nucleus. The discovery of radioactivity is considered the starting point of nuclear physics. The classical types of radioactivity, α, β, γ decay and nuclear fission, have allowed for many detailed studies of nuclear structure and have found a wide range of applications in other fields of science. According to theoretical predictions, other types of nuclear transformation should occur for very short lived atomic nuclei. In recent experiments at the GANIL and GSI laboratories, two-proton radioactivity was observed for the first time in the decay of proton-rich ⁴⁵Fe. (authors)

[en] 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 T_z = -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 280 ⁴²Cr, 50 ⁴⁵Fe and 100 ⁴⁹Ni isotopes, for which no experimental information about the decay is available

[en] 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 T_Z = -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 280 ⁴²Cr, 50 ⁴⁵Fe and 100 ⁴⁹Ni isotopes, for which no experimental information about the decay is available

[en] In the process of electron capture by the nucleus an electron neutrino is emitted carrying away practically all available energy equal to Q-B, where Q is the decay energy and B is the binding energy of the captured electron. With the relative probability of the order of 10^-4 the neutrino is accompanied by a photon. In this second-order radiative process (called internal bremsstrahlung - IB) the available energy is shared statistically between the neutrino and the photon, which results in a continuous energy spectrum of emitted photons. The aim of this paper is the IB process accompanying forbidden transitions, specifically those in which spin difference between initial and final nuclear states is equal to 2. Then, if the parities of those nuclear states are different, the authors have the first forbidden unique transition, otherwise (no change of parity) the transition is second forbidden nonunique (2nu)

[en] The decay of extremely neutron-deficient isotope ⁴⁵Fe has been studied by using a new type of gaseous detector in which a technique of optical imaging is used to record tracks of charged particles. The two-proton radioactivity and the beta-decay channels accompanied by proton(s) emission were clearly identified. For the first time, the angular and energy correlations between two protons emitted from the ⁴⁵Fe ground-state were measured. The obtained distributions were confronted with predictions of a three-body model. Studies of beta-decay channels of ⁴⁵Fe provided first unambiguous evidence for the beta-delayed three proton emission

[en] An island of isomers have recently been observed on both sides of the N=40 shell below the Ni isotopes. Isomeric states in the 65Fe and 67Fe allow the knowledge of the single particle structure around the g9/2 shell. Moreover, the excitation energy of the first 2+ and 4+ states in the 68Fe have been established by β-γ correlation. The evolution of the structure of the Fe isotopes going far away from the valley of stability is, for the first time, given for N>40

[en] The most remote isotope from the proton drip line (by 4 atomic mass units) has been observed: ³¹K. It is unbound with respect to three-proton (3p) emission, and its decays have been detected in flight by measuring the trajectories of all decay products using microstrip detectors. The 3p emission processes have been studied by the means of angular correlations of ²⁸S + 3p and the respective decay vertices. The energies of the previously unknown ground and excited states of ³¹K have been determined. This provides its 3p separation energy value S³p of -4.6(2) MeV. Upper half-life limits of 10 ps of the observed ³¹K states have been derived from distributions of the measured decay vertices. (authors)

No abstract available

[en] In an experiment performed at the NSCL/MSU A1900 separator the decay of ⁴⁵Fe was investigated in detail. Two-proton radioactivity channel was clearly identified and for the first time the correlations between two protons emitted from the nuclear ground state were determined. The comparison with a theoretical model indicates the genuine three-body character of this decay and sheds light on the shell structure of this exotic nucleus. The β decay channels of ⁴⁵Fe, followed by one-, two-, and three-proton emission, were also identified. The β3p decay channel was observed for the first time. The half-life of ⁴⁵Fe was found to be 2.6±0.2 ms and the 2p decay branching ratio is 70±4%. In the experiment a new type of gaseous detector has been applied in which a technique of digital imaging was used to record tracks of charged particles

[en] Recently the observation of a new type of spontaneous radioactive decay has been claimed in which two protons are simultaneously ejected by an atomic nucleus from the ground state1,2,3. Experimental data obtained for the extremely neutron-deficient nuclei 45Fe and 54Zn, were interpreted as the first evidence of such a decay mode which has been sought since 1960.4 However, the technique applied in those studies allowed only measurements of the decay time and the total energy released. Particles emitted in the decay were not identified and the conclusions had to be supported by theoretical arguments. Here we show for the first time, directly and unambiguously, that 45Fe indeed disintegrates by two-proton decay. Furthermore, we demonstrate that the decay branch of this isotope leads to various particle emission channels including two-proton and three-proton emission. To achieve this result we have developed a new type of detector V the Optical Time Projection Chamber (OTPC) in which digital photography is applied to nuclear physics for the first time. The detector records images of tracks from charged particles, allowing for their unambiguous identification and the reconstruction of decay events in three dimensions. This new and simple technique provides a powerful method to identify exotic decay channels involving emission of charged particles. It is expected that further studies with the OTPC device will yield important information on nuclei located at and beyond the proton drip-line, thus providing new material for testing and improving models of very unstable atomic nuclei