$\alpha$-decay chains of the superheavy nuclei ${}^{255\text{–}350}\mathrm{Rg}$

The decay modes and half-lives of 96 isotopes of the superheavy element roentgenium (Rg) within the range of $255\le A\le 350$ come under investigation in the present paper. The isotopes which lie beyond the proton drip line are identified by calculating the one-proton and two-proton separation energies. The $\alpha$-decay half-lives are calculated using the Coulomb and proximity potential model for deformed nuclei (CPPMDN). For a theoretical comparison the $\alpha$ half-lives are also evaluated using the Viola-Seaborg semiempirical relation, the universal curve of Poenaru et al., the analytical formula of Royer, and the universal decay law of Qi et al. Spontaneous fission half-lives are computed with the shell-effect-dependent formula of Santhosh and Nithya and the semiempirical formula of Xu et al. The decay modes are predicted by comparing the $\alpha$-decay half-lives within the CPPMDN with the corresponding spontaneous fission half-lives computed by the shell-effect-dependent formula of Santhosh and Nithya. In our paper it is seen that the isotopes ${}^{255\text{–}271,273}\mathrm{Rg}$ lie beyond the proton drip line and hence decay through proton emission. The isotopes ${}^{272,274\text{–}277}\mathrm{Rg}$ exhibit long $\alpha$ chains. Three $\alpha$ chains are predicted from the isotopes ${}^{278\text{–}282}\mathrm{Rg}$. The isotopes ${}^{283\text{–}345}\mathrm{Rg}$ decay through spontaneous fission. The isotopes ${}^{346\text{–}350}\mathrm{Rg}$ are found to be stable against $\alpha$ decay. The theoretical results are compared with the available experimental results and are seen to be matching well. We hope that our predictions will be useful in future experimental investigations.

Figure 1

The comparison of the calculated $\alpha$-decay half-lives with the spontaneous fission half-lives for the isotope ${}^{272}\mathrm{Rg}$ and its decay products.

Figure 2

The comparison of the calculated $\alpha$-decay half-lives with the spontaneous fission half-lives for the isotope ${}^{274}\mathrm{Rg}$ and its decay products.

Figure 3

The comparison of the calculated $\alpha$-decay half-lives with the spontaneous fission half-lives for the isotope ${}^{275}\mathrm{Rg}$ and its decay products.

Figure 4

The comparison of the calculated $\alpha$-decay half-lives with the spontaneous fission half-lives for the isotope ${}^{276}\mathrm{Rg}$ and its decay products.

Figure 5

The comparison of the calculated $\alpha$-decay half-lives with the spontaneous fission half-lives for the isotope ${}^{277}\mathrm{Rg}$ and its decay products.

Figure 6

The comparison of the calculated $\alpha$-decay half-lives with the spontaneous fission half-lives for the isotope ${}^{278}\mathrm{Rg}$ and its decay products.

Figure 7

The comparison of the calculated $\alpha$-decay half-lives with the spontaneous fission half-lives for the isotope ${}^{279}\mathrm{Rg}$ and its decay products.

Figure 8

The comparison of the calculated $\alpha$-decay half-lives with the spontaneous fission half-lives for the isotope ${}^{280}\mathrm{Rg}$ and its decay products.

Figure 9

The comparison of the calculated $\alpha$-decay half-lives with the spontaneous fission half-lives for the isotope ${}^{281}\mathrm{Rg}$ and its decay products.

Figure 10

The comparison of the calculated $\alpha$-decay half-lives with the spontaneous fission half-lives for the isotope ${}^{282}\mathrm{Rg}$ and its decay products.