b-NMR

[paper] Erosion of N=20 shell in ³³Al investigated through the ground-state electric quadrupole moment

Erosion of N=20 shell in ³³Al investigated through the ground-state electric quadrupole moment

K. Shimada et al.

doi: 10.1016/j.physletb.2012.07.030

Electric quadrupole moment Q of the ground state has been measured by means of β-NMR spectroscopy using a spin-polarized beam produced in a projectile fragmentation reaction. The obtained Q moment, |Q_exp(³³Al)|=132(16) emb, shows a significant excess from the prediction of shell model calculations within the sd shell. The result indicates sizable admixing of pf intruder configurations in the ground state, demonstrating that the N=20 shell closure certainly erodes in ³³Al, a nucleus located on the border of the island of inversion. Comparison was made with predictions of the Monte Carlo shell model, and also a particle-vibration coupling model treating the neutron pairing correlations in the ground state of ³³Al. Again, a significant admixture of pf intruder configurations to the ground state was needed in both theoretical approaches to explain the observed large Q.

Aug 14, 2012 by Theo experiment 0

[paper] Hyperfine field and hyperfine anomalies of copper impurities in iron

Hyperfine field and hyperfine anomalies of copper impurities in iron

V. V. Golovko et al.

doi: 10.1103/PhysRevC.84.014323

A new value for the hyperfine magnetic field of copper impurities in iron is obtained by combining resonance frequencies from experiments involving β-NMR on oriented nuclei on ⁵⁹Cu, ⁶⁹Cu, and ⁷¹Cu with magnetic moment values from collinear laser spectroscopy measurements on these isotopes. The resulting value, i.e., B_hf(CuFe) = -21.794(10) T, is in agreement with the value adopted until now but is an order of magnitude more precise. It is consistent with predictions from ab initio calculations. Comparing the hyperfine field values obtained for the individual isotopes, the hyperfine anomalies in Fe were determined to be ⁵⁹Δ⁶⁹=0.15(9)% and ⁷¹Δ⁶⁹=0.07(11)%.

Jul 22, 2011 by Theo g factor 0

[paper] g factor of the ⁴⁴Cl ground state: Probing the reduced Z=16 and N=28 gaps

g factor of the ⁴⁴Cl ground state: Probing the reduced Z=16 and N=28 gaps

M. De Rydt et al.

doi: 10.1103/PhysRevC.81.034308

The g factor of the ⁴⁴Cl ground state is measured at the LISE fragment separator at the Grand Acclérateur National d’Ions Lourds (GANIL) using the β nuclear magnetic resonance technique, resulting in g(⁴⁴Cl)=(-)0.2749(2). An analysis of the g factor value and of the theoretical level scheme in the shell-model framework reveals the presence of odd-proton s_1/2 configurations and neutron excitation across the N=28 shell gap in the ground state of ⁴⁴Cl. In addition, the measured g factor strongly supports a 2^– spin assignment for the ⁴⁴Cl ground state.

Mar 19, 2010 by Theo experiment g factor theory 0

[paper] Doubly-magic nature of ⁵⁶Ni: Measurement of the ground state nuclear magnetic dipole moment of ⁵⁵Ni

Doubly-magic nature of ⁵⁶Ni: Measurement of the ground state nuclear magnetic dipole moment of ⁵⁵Ni

J.S. Berryman et al.

doi: 10.1103/PhysRevC.79.064305

The nuclear magnetic moment of the ground state of ⁵⁵Ni (I^π=3/2^–, T_1/2=204 ms) has been deduced to be |&mul(⁵⁵Ni)|=(0.976&plusminus;0.026) μ_N using the β-ray detecting nuclear magnetic resonance technique. Results of a shell model calculation in the full fp shell model space with the GXPF1 interaction reproduce the experimental value. Together with the known magnetic moment of the mirror partner ⁵⁵Co, the isoscalar spin expectation value was extracted as <Σσ_z>=0.91&plusminus;0.07. The <Σσ_z> shows a trend similar to that established in the sd shell. The present theoretical interpretations of both &mul(⁵⁵Ni) and <Σσ_z> for the T=1/2, A=55 mirror partners support the softness of the ⁵⁶Ni core.

Jun 5, 2009 by Theo experiment 0

[paper] Ground-state electric quadrupole moment of ³¹Al

Ground-state electric quadrupole moment of ³¹Al

D. Nagae et al.

The ground-state electric quadrupole moment of ³¹Al(I^π=5/2⁺,T_1/2=644(25) ms) has been measured by means of β-ray-detected nuclear magnetic resonance spectroscopy using a spin-polarized ³¹Al beam produced in the projectile fragmentation reaction. The obtained Q moment, |Q_exp(³¹Al)|=112(32) e mb, is in agreement with conventional shell model calculations within the sd valence space. Previous results on the magnetic moment also support the validity of the sd model in this isotope, and thus it is concluded that ³¹Al is located outside of the island of inversion

Feb 18, 2009 by Theo experiment 0

[paper] 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"

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 et al.

doi: 10.1016/j.physletb.2007.11.017

For the first time the g factor of an isotope beyond N=20 near the "island of inversion" has been measured. A ³⁴Al radioactive beam was produced in a one-neutron pickup reaction on a ³⁶S 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 ³⁴Al, |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 scale shell model calculations reveals that a dominant amount of intruder components is needed in the ³⁴Al 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.

Jan 10, 2008 by Theo experiment g factor 0

[paper] Magnetic moments of ³⁰₁₃Al₁₇ and ³²₁₃Al₁₉

Magnetic moments of ³⁰₁₃Al₁₇ and ³²₁₃Al₁₉

H. Ueno et al.

doi: 10.1016/j.physletb.2005.04.037

Ground-state magnetic moments of ³⁰Al and ³²Al were measured
with the β-NMR method using radioactive-isotope beams spin-polarized in the projectile-fragmentation
reaction. Polarization of sizes |P|=0.5–1% were obtained in spite of the large numbers of nucleons
that are removed from the projectile ⁴⁰Ar, providing a promising prospect that
substantial polarizations are obtained even in fragment nuclei that are far removed from the projectile nucleus.
The obtained μ moments, |μ_exp(³⁰Al)|=3.010(7) μ_N
and |μ_exp(³²Al)|=1.959(9) μ_N, are in agreement with
shell model calculations within the sd valence space, although a reduction in the energy-gap between
the sd and pf states is predicted for ³²Al in recent theoretical studies.

Jun 2, 2005 by Theo g factor 0

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