α-decay chains of the superheavy nuclei 255-350Rg

The decay modes and half-lives of 96 isotopes of the superheavy element roentgenium (Rg) within the range of 255 <= A <= 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 ofXu et al. The decay modes are predicted by comparing the alpha-decay half-lives within the CPPMDNwith 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 isotope (255-271,273)Rg lie beyond the proton drip line and hence decay through proton emission. The isotopes (272,274-277)Rg exhibit long alpha chains. Three alpha chains are predicted from the isotopes (278-282)Rg. The isotopes (283-345)Rg decay through spontaneous fission. The isotopes (346-350)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.