g factor of the exotic N=21 isotope Al-34: probing the N=20 and N=28 shell gaps at the border of the "island of inversion"
Himpe, P Neyens, Gerda × Balabanski, D. L Belier, G Daugas, J. M de Oliveira Santos, F De Rydt, Marieke Flanagan, K. T Matea, I Morel, P Penionzhkevich, Yu. E Perrot, L Smirnova, N. A Stodel, C Thomas, J. C Vermeulen, Nele Yordanov, D. T Utsuno, Y Otsuka, T #
Elsevier science bv
Physics Letters B vol:658 issue:5 pages:203-208
For the first time the g factor of an isotope beyond N = 20 near the 'island of inversion' has been measured. A Al-34 radioactive beam was produced in a one-neutron pickup reaction on a S-36 primary beam at 77.5 MeV/u, providing a large spin-polarization for application of the P-Nuclear Magnetic Resonance (beta-NMR) method. The measured g factor of Al-34 vertical bar g vertical bar = 0.539(2), combined with results from earlier beta-decay studies, allows to firmly assign a ground state spin/parity 4(-). Comparison to large scale shell model calculations reveals that a dominant amount of intruder components is needed in the Al-34 wave function to account for the observed large magnetic moment mu = (+)2.156(16)mu(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. (c) 2007 Elsevier B.V. All rights reserved.