High-precision quadrupole moment reveals significant intruder component in 33Al20 ground state

Abstract

The electric quadrupole moment of the 33Al20 ground state, located at the border of the island of inversion, was obtained using continuous-beam beta-detected nuclear quadrupole resonance (beta-NQR). From the measured quadrupole coupling constant Q = 2.31(4) MHz in an alpha-Al2O3 crystal, a precise value for the electric quadrupole moment is extracted: Qs= 141(3) mb. A comparison with large-scale shell model calculations shows that 33Al has at least 50% intruder configurations in the ground state wave function, favoring the excitation of two neutrons across the N = 20 shell gap. 33Al therefore clearly marks the gradual transition north of the deformed Na and Mg nuclei towards the normal Z>14 isotopes.

arXiv comment6 pages, 4 figures. Accepted for publication in Physical Review C

References in corpus (8)

• The realistic collective nuclear Hamiltonian
• The merging of the islands of inversion at N=20 and N=28
• Discovery of the shape coexisting 0+ state in 32Mg by a two neutron transfer reaction
• Onset of intruder ground state in exotic Na isotopes and evolution of the N=20 shell gap
• Unveiling the intruder deformed 0${}_2^{+}$ state in ${}^{34}$Si
• Extinction of the N=20 neutron-shell closure for 32Mg examined by direct mass measurements
• Ground-state electric quadrupole moment of 31Al
• Precision measurement of the electric quadrupole moment of 31Al and determination of the effective proton charge in the sd-shell

Cited by in corpus (5)

• Evolution of shell structure in exotic nuclei
• Ab initio calculation of the potential bubble nucleus ${}^{34}$Si
• High-resolution laser spectroscopy of ${}^{27-32}$Al
• Triaxial deformation and the loss of the N = 28 shell gap
• First-principles results for electromagnetic properties of $sd$ shell nuclei