g factor of the exotic N=21 isotope 34Al: probing the N=20 and N=28 shell gaps at the border of the "island of inversion"

P. Himpe, G. Neyens, D.L. Balabanski, G. Bélier, J.M. Daugas, F. de Oliveira Santos, M. De Rydt, K.T. Flanagan, I. Matea, P. Morel, Yu.E. Penionzhkevich, L. Perrot (+7 others)
2008 Physics Letters B  
For the first time the g factor of an isotope beyond N = 20 near the 'island of inversion' has been measured. A 34 Al radioactive beam was produced in a one-neutron pickup reaction on a 36 S primary beam at 77.5 MeV/u, providing a large spin-polarization for application of the β-Nuclear Magnetic Resonance (β-NMR) method. The measured g factor of 34 Al, |g| = 0.539(2), combined with results from earlier β-decay studies, allows to firmly assign a ground state spin/parity 4 − . Comparison to large
more » ... Comparison to large scale shell model calculations reveals that a dominant amount of intruder components is needed in the 34 Al wave function to account for the observed large magnetic moment μ = (+)2.156(16)μ N . This reveals Z = 13 to be a true 'transition number' between the normal Z = 14 Si isotopes and the abnormal Z = 12 Mg isotopes. The sensitivity of this odd-odd ground state dipole moment to the N = 20, as well as the N = 28 gap, reveals that both are significantly reduced, despite Z = 13 being outside the conventional island of inversion.
doi:10.1016/j.physletb.2007.11.017 fatcat:zwcidyd2zncr5ishxqqb2mmdeu