Intruder configurations in 29^{29}Ne at the transition into the island of inversion: Detailed structure study of 28^{28}Ne

Detailed $\gamma$-ray spectroscopy of the exotic neon isotope $^{28}$Ne has been performed for the first time using the one-neutron removal reaction from $^{29}$Ne on a liquid hydrogen target at 240~MeV/nucleon. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for $^{28}$Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder $p$-wave strength providing evidence of the breakdown of the $N=20$ and $N=28$ shell gaps. Only a weak, possible $f$-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large $p$-wave and small $f$-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain

Extending the Southern Shore of the Island of Inversion to F-28

Detailed spectroscopy of the neutron-unbound nucleus F-28 has been performed for the first time following proton/neutron removal from Ne-29/F-29 beams at energies around 230 MeV=nucleon. The invariant-mass spectra were reconstructed for both the F-27((*)) + n and F-26((*)) + 2n coincidences and revealed a series of well-defined resonances. A near-threshold state was observed in both reactions and is identified as the F-28 ground state, with S-n(F-28) = -199(6) keV, while analysis of the 2n decay channel allowed a considerably improved S-n(F-27) = 1620(60) keV to be deduced. Comparison with shell-model predictions and eikonal-model reaction calculations have allowed spin-parity assignments to be proposed for some of the lower-lying levels of F-28. Importantly, in the case of the ground state, the reconstructed F-27 + n momentum distribution following neutron removal from F-29 indicates that it arises mainly from the 1p(3/2) neutron intruder configuration. This demonstrates that the island of inversion around N = 20 includes F-28, and most probably F-29, and suggests that O-28 is not doubly magic

Border of the island of inversion:Unbound states in Ne 29

The nucleus Ne29 is situated at the border of the island of inversion. Despite significant efforts, no bound low-lying intruder f7/2 state, which would place Ne29 firmly inside the island of inversion, has yet been observed. Here, the first investigation of unbound states of Ne29 is reported. The states were populated in Ne30(p,pn) and Na30(p,2p) reactions at a beam energy of around 230 MeV/nucleon, and analyzed in terms of their resonance properties, partial cross sections, and momentum distributions. The momentum distributions are compared to calculations using the eikonal, direct reaction model, allowing ℓ assignments for the observed states. The lowest-lying resonance at an excitation energy of 1.48(4) MeV shows clear signs of a significant ℓ=3 component, giving first evidence for f7/2 single particle strength in Ne29. The excitation energies and strengths of the observed states are compared to shell-model calculations using the sdpf-u-mix interaction.</p

High-spin states in 35S

Excited states in 35S were investigated by in-beam γ-ray spectroscopy using the 26Mg(18O, 2α1n) fusion-evaporation reaction The de-exciting γ-rays were measured with germanium detector arrays along with the measurement of evaporated charged particles in a 4π segmented Si detector array. The level scheme was extended up to 12470 keV. The obtained level structure is compared with the large-scale shell-model calculations. The possibility of isoscalar-pair excited states is discussed for J=(17/2) states with comparison between the experimental and theoretical results