Electric and nuclear transition strength in 30,32Mg

Collectivity of neutron-rich magnesium isotopes investigated by projected shell model calculations

“…For 32 Mg, different experimental groups give quite different data. Our calculation supports GANIL data [9], which gives the largest value compared to other groups. The calculated B(E2) values reach a maximum at [9], RIKEN [4,31], MSU [8,42], CERN [43], and Raman [44].…”

“…Our calculation supports GANIL data [9], which gives the largest value compared to other groups. The calculated B(E2) values reach a maximum at [9], RIKEN [4,31], MSU [8,42], CERN [43], and Raman [44]. 32 Mg in the whole chain of isotopes, which would imply large collectivity and the erosion of the N = 20 shell gap.…”

“…It has been pointed out that the N = 20 gap is no longer large enough to hinder the cross-shell excitations for magnesium isotopes [4], and a considerable prolate deformation was observed for the ground state of 32 Mg through the measurements of the E2 transition strength [4][5][6] and rms charge radii [7]. The lowlying excited states contain significant intruder configurations, i.e., configurations outside the sd shell [4,[8][9][10]. The normal and intruder configurations are even inverted in energies [10].…”

Shape Coexistence Near Neutron NumberN=20: First Identification of theE0Decay from the Deformed First ExcitedJπ=Schwerdtfeger1, Thirolf2, Wimmer3 et al. 2009Phys. Rev. Lett.6613962View full textAdd to dashboardCite

“…A coexistence of spherical and deformed 0 + states is predicted to exist within a small region around N=20 in the neutron-rich Mg nuclei [4,5], the 'island of inversion'. So far studies on spectroscopic properties have focused on B(E2) values between the 0 + ground state and the first excited 2 + state [6,7,8,9,10,11,12], however no excited 0 + state has been experimentally observed in these nuclei. While 32 Mg, which is conventionally considered a closed-shell nucleus, exhibits a strongly deformed ground state as indicated by the large value of B(E2;0 [6], the ground state of 30 Mg is expected to be much less deformed, whereas a (deformed) excited 0 + 2 state is predicted at an energy between 1.7 and 2 MeV [13,14,15,16] that has so far escaped observation.…”

Large-angle scattering and quasielastic barrier distributions

“…The authors of Refs. [35][36][37] argue that these large collectivities may be indicative of a static deformation of 32 Mg. On the other hand, meanfield calculations [38] as well as quasiparticle random-phase approximation (QRPA) [39] with the Skyrme interaction suggest that 32 Mg may be spherical. In fact the energy ratio between the first 4 + and the first 2 + states, E 4 + 1 /E 2 + 1 , is 2.6 [37], which is between the vibrational and rotational limits [39].…”