Two-proton radioactivity of exotic nuclei beyond proton drip-line

Abstract

To search for new candidates of the true and simultaneous two-proton (2p) radioactivity, the 2p decay energies (Q 2p ) are extracted by the Weizsäcker–Skyrme-4 (WS4) model, the finite-range droplet model (FRDM), the Koura–Tachibana–Uno–Yamada (KTUY) model and the Hartree–Fock–Bogoliubov mean-field model with the BSk29 Skyrme interaction (HFB29). Then, the 2p radioactivity half-lives are calculated within the generalized liquid drop model by inputting the four types of Q 2p values. By the energy and half-life constraints, it is found that the probable 2p decay candidates are the nuclei beyond the proton-drip line in the region of Z ≤ 50 based on the WS4 and KTUY mass models. For the FRDM mass model, the probable 2p decay candidates are found in the region of Z ≤ 44. However, the 2p-decaying candidates are predicted in the region of Z ≤ 58 by the HFB29 mass model. It means that the probable 2p decay candidates of Z > 50 are only predicted by the HFB29 mass model. Finally, the competition between the true 2p radioactivity and α-decay for the nuclei above the N = Z = 50 shell closures is discussed. It is shown that 101Te, 111Ba and 114Ce prefer to 2p radioactivity and the dominant decay mode of 107Xe and 116Ce is α-decay.

Two-proton radioactivity of ground and excited states within a unified fission model *

“…Encouraged by the success of the UFM, we attempt to predict the half-lives of the most probable decay candidates within it. In our recent study [89], we predicted the half-lives of the most probable decay candidates within the GLDM by inputting the values extracted from the mass tables of the Weizsäcker-Skyrme-4 model [90], the finite-range droplet model [91], the Koura-Tachibana-Uno-Yamada model [92], and the Hartree-Fock-Bogoliubov mean-field model with the BSk29 Skyrme interaction [93]. It was shown that the uncertainties of the decay half-lives are rather large due to the strong model dependence of the values; and therefore, accurate values are crucial for predicting the radioactive half-lives.…”

“…Since the mechanism of radioactivity is similar to that of -decay [96][97][98][99][100], the cluster-like or fission-like models that can describe -decay can reproduce the experimental half-lives of radioactivity. Recently, an extended constraint criterion on the half-life, -12< <2 s, was proposed to identify the most probable decay candidates [89] for future 2p experiments, based on the work of Olsen et al [62]. According to the constraint condition, the most probable decay candidates listed in Table 2 are 24 P, 39 Ti, 40 V, 42 Cr, 43 Mn, 47 Co, 49 Ni, 56,57 Ga, 58,59 Ge, 60,61 As, 63 Se, 65,66 Br, and 68 Kr.…”

Roles of tensor force and pairing correlation in two-proton radioactivity of halo nuclei*

“…Similarly, the tensor effect of β on and τ can be discussed by the competition between and in Eq. (26). However, the effect from is weaker than that from .…”

Two-proton radioactivity within Coulomb and proximity potential model *

“…However, by reason of the limitations of experimental techniques, it is extremely difficult to observe the 2p radioactivity phenomenon from nuclear ground state in the early experiments. With the development of experimental facilities and detection technologies, the not true 2p radioactivity (Q 2p > 0 and Q p > 0, where Q p and Q 2p are the released energy of proton radioactivity and two-proton radioactivity, respectively) were observed from a very short-lived nuclear ground state, such as 6 Be [23], 12 O[24] and 16 Ne [25]. In 2002, the true 2p radioactivity (Q 2p > 0 and Q p < 0) [26] was discovered from ground state of 45 Fe at GSI [27] and GANIL [28], respectively.…”

“…Two-proton ( ) radioactivity was firstly predicted by Zel'dovich in 1960s, followed by the description of this process given by Goldansky [1][2][3][4]. Subsequently, a great deal of effort on experiments and/or theories have been devoted to exploring the probable radioactivity phenomena, which opens a new window for study of the decay modes and ground-state masses of exotic nuclei near or beyond the proton drip line [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Moreover, the study of radioactivity can extract abundant nuclear structure information, such as the sequences of particle energies, the wave function of the two emitted protons, the deformation effect and so on [20][21][22].…”