Intruder dominance in the 02+ state of Mg32 studied with a novel technique for in-flight decays

Shell Model calculations of nuclear structure in ʺIsland of inversionʺ N=20 region: 32-36Mg isotopes

“…4, good agreement was revealed between the first excited state 2 + 1 at 0.98 MeV with the experimental data [40,41] and previous theoretical works [25,41,42]. The calculations further revealed that there is an energy at 1.98 MeV belonging to the 0 + 2 This energy is the best compatible value to the experimental value of 1.058 MeV [40,43], more than the theoretical value in Ref. [61].…”

In-beam γ -ray spectroscopy of Cr62,64

“…Regarding the impact of unobserved feeding, potentially missed high-spin feeders of the 6 + 1 state would preserve the broad shape of the momentum distribution, while indirect feeding to the 0 + 2 level would most probably be due to decay branches from higher-lying 2 + states, only marginally broadening the observed 0 + momentum distribution, in particular as compared to that of the 6 + state. We note that two-nucleon knockout reactions are typically rather selective, reducing the expected level density, and that low-lying 0 + states have been notoriously hard to find [21][22][23][24], in part because their population appears to be selective with only minor indirect feeding in typical reactions.…”

“…These have been successful in predicting the energies of the only two excited states, 2 + 1 and (4 + 1 ) [12], known for the key nucleus 64 Cr at the center of the island. While shape coexistence has been prominently displayed by nuclei at the boundary of islands of inversion, for example in 34 Si (N = 20 island of inversion) [21] and in 68 Ni as discussed above, a low-lying, presumably shape-coexisting 0 + state has also been established in 32 Mg [22,23], at the heart of the N = 20 island of inversion, as well as in collective 44 S [24][25][26] at N = 28. Given the stark similarities between the N = 20, 28 and the N = 40 islands of inversion, one may also anticipate finding low-lying shape coexistence in the neutron-rich Cr isotopes.…”

In-beam $γ$-ray spectroscopy of $^{32}$Mg via direct reactions

“…These measurements established the large collectivity of this nucleus with a strong deformation of the ground state. In 2010, the 0 + 2 state was experimentally observed in the t( 30 Mg,p) reaction [19], and later the existence of this state was confirmed by an in-beam γ-ray spectroscopy experiment [21]. From a simplified point of view, the 0 + 2 state in 32 Mg is interpreted as a counterpart of the near-spherical ground state of 30 Mg [32].…”

“…The structure of this nucleus has been studied over the past several decades, and its low 2 + 1 [11] energy and high B(E2; 0 + 1 → 2 + 1 ) [12,13] value, which signify the breakdown of magicity, have been well established. To date, much effort has been devoted to a proper and unified description of the island of inversion [4,[14][15][16], and it continues to be an interesting subject to study experimentally [17][18][19][20][21]. To differentiate between various structural models, confrontation with additional, high-quality experimental data is required.…”