Quest for two-proton radioactivity

Abstract

Two-proton emission half-lives ($T_{1/2}^{2p}$ values) of nuclei are determined employing the interaction potential involving Coulomb and proximity potentials. We compare $T_{1/2}^{2p}$ values with those calculated using the empirical method, and to assess the precision of the present model in reproducing the experimental half-lives, a comparison is made with experimental ones as well. In light and medium mass region, we have reported few nuclei, viz. $^{22}$Si, $^{26}$S, $^{30}$Ar, $^{34}$Ca, $^{36,38}$Ti, $^{40,42}$Cr, $^{52}$Zn, $^{58,60}$Ge, $^{62}$Se and $^{64,66,68}$Kr, as two-proton emitters. Moreover, such radioactivity in $^{60}$Ge and $^{68}$Kr nuclei can be identified experimentally. However, we require disintegration energy ($Q_{2p}$ values) as an input in order to predict the $T_{1/2}^{2p}$ values of experimentally unknown even–even superheavy nuclei (SHN), and employing periodic orbit theory within microscopic–macroscopic formalism, we have calculated $Q_{2p}$ values of these nuclei whose atomic number lies between 118 and 126. Subsequently, we determine the logarithmic values of $T_{1/2}^{2p}$’s for even–even unknown SHN and compare the obtained results with those calculated exploiting the empirical method. Also, the study of spontaneous fission half-lives, $\alpha$-decay half-lives and branching ratios leads us to establish that no signatures of two-proton radioactivity exist in the superheavy region. We believe that such predictions may help in the experimental identification of 2p-radioactivity in the laboratory.