Large collectivity of 34Mg

In-beamγ-ray spectroscopy ofMg35and

“…To put the predicted deformation into perspective, for the N = 22 isotone 34 Mg, the MCSM calculates B(E2; 0 + → 2 + 1 ) = 552 e 2 fm 4 (in agreement with experiment [7,9]) and Q(2 The level scheme predicted by the conventional shell model calculations based on the SDPF-U effective interaction, which does not allow for neutron intruder configurations, has the levels in the same order but predicts the 5/2 + first excited state to be within 123 keV of the 3/2 + ground state (see Fig. 5).…”

“…In this region, driven largely by the spin-isospin parts of the nuclear force [3], neutron np-nh "intruder" configurations of ν(sd) −n (f p) +n character (labeled nhω) gain "correlation energy" [4] with respect to the normal-order configurations and dominate the wave functions of low-lying states including the ground states -signaling the breakdown of N = 20 as a magic number in these nuclei. The resulting onset of collectivity was quantified with inelastic scattering experiments [5][6][7][8][9][10] and inferred from measurements of the 2 + 1 excitation energies [11][12][13][14] on even-even nuclei out to 32 Ne and 36 Mg at Z = 10 and Z = 12, respectively. These collective properties of even-even nuclei are rather well described by state-of-the-art Monte Carlo Shell-Model (MCSM) calculations (SDPF-M effective interaction) that allow for unrestricted mixing of neutron particle-hole configurations across the N = 20 shell gap.…”

Correlations beyond the mean field in magnesium isotopes: angular momentum projection and configuration mixing

“…Recently, evidence for a rotational band in 31 Na has also been obtained [17]. Although indirect, another evidence for the deformed nature of the 32 Mg ground state comes from the strong ground state deformation of 34 Mg inferred from the large value of the B(E2, 0 + 1 → 2 + 1 ) transition probability measured [18] in this nucleus and the E(4 + )/E(2 + ) ratio of 3.18 [19,20] which is very close to the rotational limit. Further evidence for deformed ground states in the neutron rich Mg isotopes have also been obtained experimentally [21][22][23].…”

Measurements of interaction cross sections for22–35Na isotopes

“…Recently, the region of neutron-rich Ne, Na and Mg isotopes around N = 20, known as "island of inversion [3]" has been extensively studied. In this region, in spite of having neutron number around magic number 20, it has been reported that 32 Mg and 34 Mg are strongly deformed [4,5], and 31 Ne has a neutron-halo structure a present address: National Institute of Radiological Sciences, Chiba 263-8555, Japan;e-mail: ssuzuki@nirs. [7].…”