Two-proton radioactivity within Coulomb and proximity potential model

Considering the preformation probability of the two emitted protons in the parent nucleus,we extend the Coulomb and proximity potential model(CPPM)to systematically study two-proton(2p)radioactivity half-lives of the nuclei close to proton drip line.The proximity potential chosen is Prox.81 proposed by Blocki et al.in 1981.Furthermore,we apply this model to predict the half-lives of possible 2p radioactive candidates whose 2p radioactivity is energetically allowed or observed but not yet quantified in the evaluated nuclear properties table NUBASE2016.The predicted results are in good agreement with those from other theoretical models and empirical formulas,namely the effective liquid drop model(ELDM),generalized liquid drop model(GLDM),Gamow-like model,Sreeja formula and Liu formula.

Systematic study on α-decay half-lives of uranium isotopes with a screened electrostatic barrier

In the present work,we systematically study the α-decay half-lives of uranium(Z=92) isotopes based on the Gamow model with a screened electrostatic barrier.There are only two adjustable parameters in our model i.e.the parameter g and the screening parameter t in the Hulthen potential for considering the screened electrostatic effect of the Coulomb potential.The calculated results are in good agreement with experimental data,and the corresponding root-mean-square(rms) deviations of uranium isotopes with α transition orbital angular momentum l=0 and l=2 are 0.141 and 0.340,respectively.Moreover,we extend this model to predict α-decay half-lives of uranium isotopes whose a decay is energetically allowed or observed but not yet quantified in NUBASE2020.For comparison,the modified Hatsukawa formula(XLZ),the unified Royer formula(DZR),the universal decay law(UDL) and the Viola-Seaborg-Sobiczewski formula(VSS) are also used.The predictions are basically consistent with each other.Meanwhile,the results also indicate that N=126 shell closure is still robust at Z=92 and the spectroscopic factor S_(α) is almost the same for uranium isotopes with the same l.