Magnetic Moments

[paper] Nuclear ground-state spin and magnetic moment of ²¹Mg

Nuclear ground-state spin and magnetic moment of ²¹Mg

J. Krämer et al.

doi: 10.1016/j.physletb.2009.06.063

We present the results of combined laser spectroscopy and nuclear magnetic resonance studies of ²¹Mg. The nuclear ground-state spin was measured to be I=5/2 with a magnetic moment of &mul;=−0.983(7)μ_N. The isoscalar magnetic moment of the mirror pair is evaluated and compared to the extreme single-particle prediction and to nuclear shell-model calculations. We determine an isoscalar spin expectation value of 〈σ〉=1.15(2), which is significantly greater than the empirical limit of unity given by the Schmidt values of the magnetic moments. Shell-model calculations taking into account isospin non-conserving effects, are in agreement with our experimental results.

Aug 3, 2009 by Theo experiment 0

[paper] Hyperfine field of einsteinium in iron and nuclear magnetic moment of ²⁵⁴Es

Hyperfine field of einsteinium in iron and nuclear magnetic moment of ²⁵⁴Es

N. Severijns et al.

10.1103/PhysRevC.79.064322

The angular distributions of γ rays and α particles from oriented ²⁵⁰Bk, ^253,254Es, and ²⁵⁵Fm nuclei were investigated to extract hyperfine interaction information for these actinide impurities in an iron host lattice. The hyperfine field of einsteinium in iron was found to be |B_hf(EsFe̲ |)=396(32) T. With this value the magnetic moment of ²⁵⁴Es was then determined as |μ|=4.35(41) μ_N.

Jun 29, 2009 by Theo experiment 0

[paper] Up to N³LO heavy-baryon chiral perturbation theory calculation for the M1 properties of three-nucleon systems

Up to N³LO heavy-baryon chiral perturbation theory calculation for the M1 properties of three-nucleon systems

Y.-H. Song et al.

10.1103/PhysRevC.79.064002

M1 properties, comprising magnetic moments and radiative capture of thermal neutron observables, are studied in two- and three-nucleon systems. We use meson exchange current derived up to N³LO using heavy baryon chiral perturbation theory à la Weinberg. Calculations have been performed for several qualitatively different realistic nuclear Hamiltonians, which permits us to analyze model dependence of our results. Our results are found to be strongly correlated with the effective range parameters such as binding energies and the scattering lengths. Taking into account such correlations, the results are in good agreement with the experimental data with small model dependence.

Jun 22, 2009 by Theo 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] Nuclear structure of the even-even argon isotopes with a focus on magnetic moments

Nuclear structure of the even-even argon isotopes with a focus on magnetic moments

S.J.Q. Robinson et al.

10.1103/PhysRevC.79.054322″

We study the role of configuration mixing in the heavier even-even isotopes of argon. We begin by limiting the configurations of the even-even Ar isotopes to (d_3/2²)_&pi (f_7/2ⁿ)_ν. There, due to the particular location in this shell-model space of ⁴⁰Ar and ⁴⁴Ar, we find that the spectra, B(E2)’s, and magnetic moments of these two nuclei are identical. Any deviation from this equality is direct evidence of configuration mixing. In a larger shell-model space there are significant differences between these two nuclei, with ⁴⁴Ar being more collective. We also consider other even-even isotopes of argon and study how their nuclear structure effects evolve with N. We compare in the full 0ℏ ω space (sd)_π (fp)_ν the results of calculations with the WBT interaction and with the newer SDPF, denoted SDPF-U, interaction.

May 18, 2009 by Theo theory 0

[paper] g factors of first 2⁺ states of neutron-rich Xe, Ba, and Ce isotopes

g factors of first 2⁺ states of neutron-rich Xe, Ba, and Ce isotopes

C. Goodin et al.

10.1103/PhysRevC.79.034316

Using new techniques developed for measuring angular correlations with large detector arrays, the g factors of 2⁺ states in ^140,142Xe are measured for the first time by the method of correlation attenuation in randomly oriented magnetic fields. g factors in ¹⁴⁶Ba and ^146,148Ce are measured to establish the method by comparison with previous values. The results are discussed in terms of IBM-2 and rotation-vibration models.

Mar 26, 2009 by Theo experiment g factor 0

[paper] Charge radii and electromagnetic moments of Li and Be isotopes from the ab initio no-core shell model

Charge radii and electromagnetic moments of Li and Be isotopes from the ab initio no-core shell model

C. Forssén et al.

Recently, charge radii and ground-state electromagnetic moments of Li and Be isotopes were measured precisely. We have performed large-scale ab initio no-core shell model calculations for these isotopes using high-precision nucleon-nucleon potentials. The isotopic trends of our computed charge radii and quadrupole and magnetic-dipole moments are in good agreement with experimental results with the exception of the ¹¹Li charge radius. The magnetic moments are in particular well described, whereas the absolute magnitudes of the quadrupole moments are about 10% too small. The small magnitude of the ⁶Li quadrupole moment is reproduced, and with the CD-Bonn NN potential, also its correct sign.

Feb 25, 2009 by Theo theory 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] Quadrupole moments of neutron-deficient ^20,21Na

Quadrupole moments of neutron-deficient ^20,21Na

K. Minamisono et al.

doi: 10.1016/j.physletb.2009.01.006

The electric-quadrupole coupling constant of the ground states of the proton drip line nucleus ²⁰Na (I^π=2⁺, T_1/2=447.9 ms) and the neutron-deficient nucleus ²¹Na (I^π=3/2⁺, T_1/2=22.49 s) in a hexagonal ZnO single crystal were precisely measured to be |eqQ/h|=690±12 kHz and 939±14 kHz, respectively, using the multi-frequency β-ray detecting nuclear magnetic resonance technique under presence of an electric-quadrupole interaction. An electric-quadrupole coupling constant of ²⁷Na in the ZnO crystal was also measured to be |eqQ/h|=48.4±3.8 kHz. The electric-quadrupole moments were extracted as |Q(²⁰Na)|=10.3±0.8 efm² and |Q(²¹Na)|=14.0±1.1 efm², using the electric-coupling constant of ²⁷Na and the known quadrupole moment of this nucleus as references. The present results are well explained by shell-model calculations in the full sd-shell model space.

Feb 16, 2009 by Theo experiment 0

[paper] Quantum Monte Carlo calculations of magnetic moments and M1 transitions in A≤7 nuclei including meson-exchange currents

Quantum Monte Carlo calculations of magnetic moments and M1 transitions in A≤7 nuclei including meson-exchange currents

L.E. Marcucci et al.

doi: 10.1103/PhysRevC.78.065501

Green’s function Monte Carlo calculations of magnetic moments and M1 transitions including two-body meson-exchange current (MEC) contributions are reported for A≤7 nuclei. The realistic Argonne v₁₈ two-nucleon and Illinois-2 three-nucleon potentials are used to generate the nuclear wave functions. The two-body meson-exchange operators are constructed to satisfy the continuity equation with the Argonne v₁₈ potential. The MEC contributions increase the A=3,7 isovector magnetic moments by 16% and the A=6,7 M1 transition rates by 17–34%, bringing them into very good agreement with the experimental data.

Dec 10, 2008 by Theo g factor theory 0

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