Speaker
Description
Recently, elements up to oganesson have been discovered, completing the seventh period of the periodic table. Search for new elements of the eighth period is being conducted at several facilities. At RIKEN, element 119 is being searched using a $^{51}$V+$^{248}$Cm hot fusion reaction. Since the production rate of the superheavy elements is extremely low and even a few percent change in the reaction energy can reduce it by more than one order of magnitude, the reaction energy is a crucial experimental parameter in the search of new elements. However, its theoretical predictions range widely, and it is difficult to estimate it theoretically at this moment. Under these circumstances, we have been developing a method to estimate the optimal reaction energy based on the experimentally obtained quasielastic barrier distribution [1,2].
Although this estimation method has been investigated while fixing the target particle as $^{248}$Cm and changing the beam from $^{22}$Ne to $^{48}$Ca, there has been no systematic study while fixing the beam as $^{51}$V and changing the target. It is important to investigate the relation between the optimal reaction energy and the barrier distribution by changing the target particles in a wide range to extend our knowledge to $^{248}$Cm, which is the heaviest target that we use.
In this study [3], we measured the fusion reaction and quasielastic scattering of the $^{51}$V+$^{159}$Tb system at SRILAC using GARIS-III [4]. The former and the latter data are used to determine the optimal reaction energy and the quasielastic barrier height respectively, which are compared to investigate the mechanism of the heavy-ion fusion reaction involving a deformed target nucleus. The results support the hypothesis that nuclear deformation is crucial in determining the optimal reaction energy in fusion reactions. In this presentation, we will report on the measurement methods, analysis, and results.
[1] T. Tanaka et al., Phys. Rev. Lett. 124, 052502 (2020).
[2] M. Tanaka, S. Sakaguchi et al., J. Phys. Soc. Jpn. 91, 084201 (2022).
[3] P. Brionnet et al., accepted for publication in Phys, Rev. C
[4] H. Sakai et al., Eur. Phys. J. A 58, 238 (2022).
