Background. In the “cold” fusion reactions based on the use of lead and bismuth targets, the proton-rich isotopes of superheavy (SH) elements up to $Z=113$ have been produced. More neutron-rich isotopes of SH elements (up to $Z=118$) have been synthesized in “hotter” fusion reactions of ${}^{48}$Ca with actinide targets. $\alpha$-decay half-lives of different isotopes of the same SH elements (for example, 112) were found to vary by several orders of magnitude. This indicates strong shell effects in this area of the nuclear map. The understanding of these effects and other properties of SH nuclei is strongly impeded by the absence of experimental data on decay properties of the not-yet-synthesized isotopes of SH elements located between those produced in the “cold” fusion reactions and those produced in the “hot” fusion reactions and also by the yet missing neutron-enriched isotopes of these elements.

Purpose. In this paper we search for the optimal fusion reactions which may be used to fill this gap of the nuclear map and significantly extend the area of known SH nuclei.

Method. For the calculation of the cross sections we use the same approach which was employed earlier for successful predictions of all ${}^{48}$Ca induced fusion reactions.

Results. Several fusion reactions of the stable projectiles ${}^{40}$Ar, ${}^{44}$Ca, and ${}^{48}$Ca with different isotopes of actinides (lighter and heavier than those that have been already utilized in the Dubna experiments) could be used for synthesis of new SH nuclei. Predicted cross sections for the production of new isotopes of SH nuclei were found to be quite large, and the corresponding experiments can be easily performed at existing facilities. For the first time a “narrow pathway” to the middle of the island of stability was found owing to possible ${\beta }^{+}$ decay of SH nuclei ${}^{291}$115 and ${}^{291}$114 which could be formed in ordinary fusion reactions.

• Received 2 December 2011

DOI:https://doi.org/10.1103/PhysRevC.85.014608