Hyperheavy nuclei: Existence and stability

What are the limits of the existence of nuclei? What are the highest proton numbers Z at which the nuclear landscape and periodic table of chemical elements cease to exist? These deceivably simple questions are difficult to answer especially in the region of hyperheavy (Z >= 126) nuclei. We present the covariant density functional study of different aspects of the existence and stability of hyperheavy nuclei. For the first time, we demonstrate the existence of three regions of spherical hyperheavy nuclei centered around (Z similar to 138, N similar to 230), (Z similar to 156, N similar to 310) and (Z similar to 174, N similar to 410) which are expected to be reasonably stable against spontaneous fission. The triaxiality of the nuclei plays an extremely important role in the reduction of the stability of hyperheavy nuclei against fission. As a result, the boundaries of nuclear landscape in hyperheavy nuclei are defined by spontaneous fission and not by the particle emission as in lower Z nuclei. Moreover, the current study suggests that only localized islands of stability can exist in hyperheavy nuclei. (C) 2018 The Authors. Published by Elsevier B.V.