Spectroscopy of the unbound neutron-rich nucleus ³⁰F

The “Islands of Inversion(IoI)”, specific neutron rich regions in the nuclear chart showing the erosion of shell structure, are highlights in rare-isotope nuclear physics. Even the most classical one, Z=10~12, N~20, is still not yet fully understood. The south boundary of this IoI has not been yet established due to scarce experimental data especially for Z<10. This region is also interesting in terms of “Oxygen anomaly”, a sudden change of the neutron drip line from N=16 to 22 when the atomic number changes from Z=8 to 9. Theoretically, it is suggested that three nucleon forces play an important role in instability of the O isotopes[1]. Experimental studies for neutron rich F and O isotones are thus highly needed. We report on the experimental study of the unbound nucleus ³⁰F which has never been observed so far. Its invariant mass spectroscopy has been performed using the 1p removal reaction of ³¹Ne and the charge-exchange reaction of ³⁰Ne at ~230 MeV/nucleon on a carbon target at RIBF, RIKEN. The decay products, ²⁹F and a neutron, were detected in coincidence with the SAMURAI spectrometer[2]. The preliminary results of the experiment will be discussed.

[1] T. Otsuka et al., Phys. Rev. Lett. 105, 032501 (2010).

[2]T. Kobayashi et al., Phys. Instr. Meth. B 317 (2013) 294-304.