Invariant-Mass Spectroscopy at the low-Z Shore of the Island of Inversion

The so-called "island of inversion" is a region in the nuclear landscape where shell-structure changes are observed and in particular the magic neutron number at N=20 vanishes. For those nuclei at Z=10-12 and around N=20, the shell gap at N=20 quenches and pf-shell intruder configurations become important. We address the question how strong such configurations are for very neutron-rich but Z=9 fluorine isotopes. Such exotic nuclei are produced at the radioactive-ion beam factory (Japan) at beam energies around 250 MeV/u. ${}^{29}$F* & ${}^{30}$F are studied in inverse kinematics at the SAMURAI experimental setup by (p,2p) reactions on neon isotopes. The two and one neutron-unbound states, respectively, are investigated in terms of invariant-mass spectroscopy where the decay neutrons are measured explicitly. The resulting excitation-energy spectra are compared to different shell-model based calculations. Moreover, ${}^{29}$F* shows a strong two-neutron sequential decay that is also analyzed by means of Jacobi coordinates.