Theoretical study of two-proton radioactivity. Status, predictions, and applications
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eoretical Study of Two-Proton Radioactivity. Status, Predictions, and Applications L. V. Grigorenko Joint Institute for Nuclear Research, Dubna, Russia Abstract—In this paper the survey of the current state of investigation of two-proton radioactivity and related processes (three-body decays) is presented. The three-body (core + p + p) theoretical model of two-proton radioactivity based on the hyperspherical harmonics method and approximate boundary conditions of the Coulomb’s three-body problem specific for the studied class of processes is considered. The predictions for lifetimes and correlations of decay products for “promising” two-proton emitters are given. Astrophysical applications of the theory of two-proton radioactivity are discussed. PACS numbers: 21.10.Tg, 21.45. + v, 21.60.Gx, 23.50. + z, 24.30.-v, 25.10. + s, 25.40.Lw, 25.75.Gz, 26.30. + k. DOI: 10.1134/S1063779609050049
1. INTRODUCTION The idea of two-proton radioactivity is rather old. It was proposed by Goldansky about 50 years ago in a classical paper [1]. However, for decades this problem remained in the state of stagnation. The situation has changed sharply during recent years. In 2000, the first valid quantum mechanical model of two-proton radioactivity consistently taking into account the properties of the continuous spectrum of the Coulomb’s threebody problem [2–10] was proposed. Further development demonstrated its high predictive power. In 2002, the phenomenon of two-proton radioactivity was first experimentally discovered in a 45Fe nucleus [11, 12]. Recent years proved to be the turning point in the experimental study of this phenomenon. In 2005, the two-proton radioactivity was discovered in 54Zn [13] and possibly in 48Ni [14]. In 2006, an extremely strong two-proton branch was observed in the decay of a highly excited 21+ isomer of a 94Ag nucleus [15]. In 2007, the two-proton radioactivity was discovered in 19Mg [16] (this was also the first observation of this isotope), the emission of two protons was experimentally proven for 45Fe in [17], and finally, two-proton correlations in 45Fe were studied with good statistics in [18, 19]. In 2008, the observation of two-proton correlations was reported for 16Ne and 19Mg [20]. This progress became possible due to intensive development of the radioactive nuclear beam technique, which was one of the main tendencies in nuclear physics during the last decade. The experimental agenda includes both the extension of the search (the proton boundary of stability from 19Mg to 45Fe and from 54Zn to 100Sn has not been well studied yet), and obtaining more detailed correlation information on 2p decay in known cases (nearest candidates: 19Mg, 48Ni, and 54Zn). From the theoretical point of view the main problem in consideration of two-proton radioactivity is the three-body Coulomb continuum. In this case, both the
construction of the asymptotic (the problem which has not been solved in the analytical form and which results in cumbersome numerical calculations) and the examination of tunneling in the sub-barri
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