Tb fusion reaction for estimating the optimal reaction energy for the synthesis of element 119

We, the nSHE Research Group, are searching for new elements beyond element 118 (oganesson), i.e. element 119, at RIKEN. The probability of producing superheavy elements by fusion reactions is extremely low. Therefore, it is crucially important to determine the optimal experimental conditions to maximize the production rate, especially by predicting the optimal incident energy that maximizes the cross section. For this purpose, we have been developing a method to estimate the optimal energy based on the experimental data of quasielastic (QE) barrier distributions [1,2]. In this study, we measured the QE barrier distribution and excitation function of the evaporation-residue cross section for the ⁵¹V+¹⁵⁹Tb fusion reaction at the RIKEN superconducting heavy-ion linear accelerator facility (SRILAC [3]). This reaction system was chosen because ¹⁵⁹Tb has a large quadrupole deformation similar to that of ²⁴⁸Cm used in the search for element 119. The comparison of the QE barrier distribution and the excitation function was used to clarify the fusion reaction mechanism involving the deformed nuclei and to improve the accuracy of the method for estimating the optimal incident energy. In this presentation, we will show preliminary results of the measurement.