β -delayed two-proton decay of S27 at the proton-drip line

Cross-Shell Excitation in F and Ne Isotopes around N = 20

“…Table 1. The S n and S 2n values (in MeV) of [27][28][29][30][31][32][33] F and [28][29][30][31][32][33][34][35][36] Ne nuclei calculated by CISM, in comparison with experimental data from the Atomic Mass Evaluation Table 2020 [14]. The qualitative description of the ground states in the nuclei near the F and Ne drip line requires the consideration of the neutron cross-shell excitation beyond the (0-1)hω case.…”

“…The cross-shell excitation is also fundamental to reproducing the ground-state spin of F and Ne nuclei around N = 20. Table 2 shows the ground-state spin of [27][28][29][30][31] F and [28][29][30][31][32][33][34] Ne, given by experiments or CISM calculations. In the (0-1)hω case, the CISM calculation with the SDPF-M interaction cannot reproduce the ground-state spin of 28 F and 29,31,32 Ne, while those with SDPF-MU or with SDPF-U-SI fail, in 31 Ne.…”

“…F and Ne isotopes with N~20 are challenging to study due to their extreme protonneutron asymmetry. For instance, 31 F has been known to be bound since 1999 [13], while the unbound character of 32,33 F was not determined until 2019 [3]. In fact, to date, only the masses of the F (Ne) isotopes with mass numbers less than 30 (32) have been experimentally determined [14].…”

“…The shell model is an essential tool for the systematic understanding of the nuclear structure. Recently, it has been employed in describing light, proton-rich, exotic nuclei and the related isospin symmetry breaking [30][31][32][33], interpreting the shell evolution in the medium mass region [34,35], reproducing isomeric states in the medium [36,37] and heavy nuclei [38][39][40], and investigating the α-decay properties of heavy-mass nuclei [41,42].…”

“…Fukunishi et al employed an interaction in the model space, including the whole sd shell and the 0f 7/2 and 1p 3/2 orbits, and calculated some properties of 30 Ne, ensuring the necessity of cross-shell excitation [43]. The SDPF-M interaction, proposed by Utsuno et al, was presented with its results on the average neutron occupancy in the pf shell of even-mass [26][27][28][29][30][31][32][33][34] Ne [44]. Caurier et al proposed the SDPF-U-MIX interaction, and showed the results of 29,31 F and [30][31][32] Ne, considering the contribution of the particle-hole states in [45].…”