# Precision measurement of the electric quadrupole moment of $^{31}$Al and determination of the effective proton charge in the sd-shell

Abstract : The electric quadrupole coupling constant of the 31Al ground state is measured to be nu_Q = |eQV_{zz}/h| = 2196(21)kHz using two different beta-NMR (Nuclear Magnetic Resonance) techniques. For the first time, a direct comparison is made between the continuous rf technique and the adiabatic fast passage method. The obtained coupling constants of both methods are in excellent agreement with each other and a precise value for the quadrupole moment of 31Al has been deduced: |Q(31Al)| = 134.0(16) mb. Comparison of this value with large-scale shell-model calculations in the sd and sdpf valence spaces suggests that the 31Al ground state is dominated by normal sd-shell configurations with a possible small contribution of intruder states. The obtained value for |Q(31Al)| and a compilation of measured quadrupole moments of odd-Z even-N isotopes in comparison with shell-model calculations shows that the proton effective charge e_p=1.1 e provides a much better description of the nuclear properties in the sd-shell than the adopted value e_p=1.3 e.
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Journal articles

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Submitted on : Wednesday, June 24, 2009 - 8:58:39 AM
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### Citation

M. de Rydt, G. Neyens, K. Asahi, D. L. Balabanski, J. M. Daugas, et al.. Precision measurement of the electric quadrupole moment of $^{31}$Al and determination of the effective proton charge in the sd-shell. Physics Letters B, Elsevier, 2009, 678, pp.344-349. ⟨10.1016/j.physletb.2009.06.043⟩. ⟨in2p3-00397999⟩

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