Strongly coupled rotational band in Mg33

Abstract

The "Island of Inversion" at N ∼ 20 for the neon, sodium, and magnesium isotopes has long been an area of interest both experimentally and theoretically due to the subtle competition between 0p-0h and np-nh configurations leading to deformed shapes. However, the presence of rotational band structures, which are fingerprints of deformed shapes, have only recently been observed in this region. In this work, we report on a measurement of the low-lying level structure of 33 Mg populated by a two-stage projectile fragmentation reaction and studied with GRETINA. The experimental level energies, ground state magnetic moment, intrinsic quadrupole moment, and γ-ray intensities show good agreement with the strong-coupling limit of a rotational model.

Spectroscopic factors in the N=20 island of inversion: The Nilsson strong-coupling limit

“…In particular, as several solutions satisfy Eqs. 3, the magnetic moment alone in 33 Mg can be explained with the standard Nilsson amplitudes mentioned earlier [15]. However, those amplitudes do not reproduce the results in Table I.…”

“…As shown in this work and Ref. [15], the strong coupling limit provides a complementary view to the shell model calculations which become more challenging for heavier nuclei. Applications to other Islands of Inversions will be the subject of a future publication.…”

“…Following Ref. [15] we use g s = −3.83 and g R = 0.3. After fixing C 3/2,1 to the value determined above we solve for the values of C 7/2,3 and C 5/2,3 that reproduce µ and satisfy the wavefunction normalization condition, as shown in Fig.…”

“…In the odd-A nuclei surrounding 32 Mg, energy levels, electromagnetic transitions and magnetic moments [12][13][14][15][16] can be described in leading-order rotational motion within the Nilsson scheme. These observables are sensitive to the intrinsic wave-functions, and it is naturally of interest to map directly the amplitudes of the relevant Nilsson levels.…”

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

“…Similarly, a new state with unknown (J) has been observed in 34 Mg isotope by two separate works: P. Doornenbal [24] and S. Michimasa [71]. According to the fragmentation experiments carried out and via the laser spectroscopy technique, the last structure of 35 Mg isotopes revealed a negative parity for the ground and first excited states [10,11]. The level schemes for the ground state and excited states were proposed initially by Neyens [12].…”