6533b872fe1ef96bd12d38b1

RESEARCH PRODUCT

g factors of $^{31,32,33}$Al: Indication for intruder configurations in the $^{33}$Al ground state

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Abstract The g factors of 31,32,33 Al have been measured using the β -nuclear magnetic resonance ( β -NMR) technique on spin-polarized beams produced in the fragmentation of a 36 S (77.5 MeV/u) beam on a 9 Be 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 β -NMR curve for 32 Al implanted in a Si single crystal. The magnetic moment of the N = 20 nucleus 33 Al is obtained for the first time: μ ( Al 33 , I π = 5 / 2 + ) = 4.088 ( 5 ) μ N , while those of 31,32 Al are obtained with improved accuracy: μ ( Al 31 , I π = 5 / 2 + ) = 3.830 ( 5 ) μ N and μ ( Al 32 , I π = 1 + ) = 1.9516 ( 22 ) μ N . Comparison of the results to shell-model calculations in the sd and the sdpf shell-model spaces leads to the conclusion that 33 Al must contain some contribution from 2 p – 2 h 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.