Evidence for shape coexistence and superdeformation in 24Mg

An experimental view on shape coexistence in nuclei

“…Regardless of the assignment of the band members, the 0 + 2 state has been determined to be highly deformed. Its E0 decay was recently observed [40] to proceed with one of the largest E0 strengths observed across the entire nuclear chart, namely 10 3 × ρ 2 (E0; 0 + 2 → 0 + 1 ) = 380 (70). A two-level mixing calculation, assuming a maximum mixing scenario, leads to ∆(β 2 2 ) 0.43.…”

“…The groundstate band β 2 = 0.497 (2), extracted from the B(E2; 2 + 1 → 0 + 1 ) value via Eq. 28, implies that the superdeformed band in 24 Mg has β 2 (0 + 2 ) 1 [40]. In view of the conflicting results regarding the 4 + states discussed above, the spectroscopy of the potential members of the 0 + 2 band should be re-investigated, in particular the decay branches of the 4 + 3,4 states and their lifetimes, and the unobserved 2 + 3 → 0 + 2 transition.…”

“…Highly deformed structures were identified in 40 Ca [87], 42 Ca [88], 44 Ti [89] and 38 Ar [90] using particle spectroscopy following single-and multi-nucleon transfer reactions. A compilation of these results can be found in Ref.…”

“…[6]. In particular, two bands interpreted as based on 4p − 4h and 8p − 8h configurations were populated in 40 Ca via a 32 S( 12 C,α) 40 Ca cluster-transfer reaction [87].…”

Search for in-band transitions in the candidate superdeformed band in Si28

“…An SD band has been observed in an in-beam study of 36 Ar [7] but the corresponding structures, which theoretical studies have predicted for 24 Mg [8], 28 Si [4], and 32 S [5,9,10], have only limited experimental evidence in favor of their existence. For example, a recent internal pair measurement has determined ρ(E 0) from the excited 0 + state in 24 Mg at 6.432 MeV to the ground state, which suggests that this state is the bandhead of a highly deformed band [11].…”