Author:

Keywords:

electric quadrupole-moments, n=20 shell closure, magnetic dipole, nuclei, model, spectrometer, stability, mg-32, Science & Technology, Physical Sciences, Astronomy & Astrophysics, Physics, Nuclear, Physics, Particles & Fields, Physics, ELECTRIC QUADRUPOLE-MOMENTS, N=20 SHELL CLOSURE, MAGNETIC DIPOLE, NUCLEI, MODEL, SPECTROMETER, STABILITY, MG-32, 0105 Mathematical Physics, 0201 Astronomical and Space Sciences, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, Nuclear & Particles Physics, 49 Mathematical sciences, 51 Physical sciences

Abstract:

The g factors of Al-31,Al-32,Al-33 have been measured using the beta-nuclear magnetic resonance (beta-NMR) technique on spin-polarized beams produced in the fragmentation of a S-36 (77.5 MeV/u) beam on a Be-9 target. Nearly pure beams of Al (Z=13) isotopes were selected with the high-resolution fragment separator LISE at GANIL. An asymmetry as high as 6% has been observed in the beta-NMR curve for Al-32 implanted in a Si single crystal. The magnetic moment of the N=20 nucleus Al-33 is obtained for the first time: mu(Al-33, I pi = 5/2(+)) = 4.088(5)mu(N), while those Of Al-31,Al-32 are obtained with improved accuracy: mu(Al-31, I-pi = 5/2(+)) = 3.830(5)mu(N) and mu(Al-32, I-pi = 1(+)) = 1.9516(22)mu(N). Comparison of the results to shell-model calculations in the sd and the sdpf shell-model spaces leads to the conclusion that Al-33 must contain some contribution from 2p-2h intruder configurations in its ground-state wave function. This indicates a gradual transition from the normal sd shell Si (Z=14) isotopes to the intruder Mg (Z=12) isotopes. (c) 2006 Elsevier B.V. All rights reserved.