Orateur
Description
The limit of the nuclear stability, called neutron drip line, reflects structure of atomic nuclei with extremely proton-neutron asymmetry. It is known that the neutron drip line of oxygen isotope is 24O (Z=8, N=16), while that of fluorine is 31F (Z=9, N=22). This sudden change of the neutron drip line is called oxygen anomaly. Theoretical study [1] suggests that three-nucleon forces play an important role in the binding of the oxygen isotopes especially for N>16. This region is also interesting in terms of the island of inversion. It is well known that the N=20 shell closure disappears for magnesium and neon isotopes in the vicinity of N=20 while the shell structure for fluorine and oxygen is not clear. Recent experimental studies [2,3] suggest that the island of inversion extends to 29F (Z = 9, N = 20). It is a question whether the 28O nucleus, having the canonical magic numbers Z=8 and N=20, shows doubly magic characters or not. In these contexts, experimental study on the neutron-rich oxygen isotopes located beyond the neutron drip line is strongly desired.
Series of experiment for the unbound oxygen isotopes 25-28O has been performed with the SAMURAI setup [4] at RI Beam Factory (RIBF). Results of the experiments and related studies will be presented in the talk.
References
[1] T. Otsuka et al., Phys. Rev. Lett. 105, 032501 (2010).
[2] P. Doornenbal et al., Phys. Rev. C 95, 041301(R) (2017).
[3] S. Bagchi et al., Phys. Rev. Lett.124, 222504 (2020).
[4] T. Kobayashi et al., Nucl. Instrum. Methods Phys. Res., Sect. B 317, 294 (2013).
