quadrupole moment

[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] Self-consistent calculations of quadrupole moments of the first 2⁺ states in Sn and Pb isotopes

Self-consistent calculations of quadrupole moments of the first 2⁺ states in Sn and Pb isotopes

D. Voitenkov et al.

doi: 10.1103/PhysRevC.85.054319

A method of describing static moments of excited states and transitions between excited states is formulated for nonmagic nuclei within the Green’s function formalism. Quadrupole moments of the first 2⁺ states in tin and lead isotope chains are calculated self-consistently using the energy density functional by Fayans et al. [Nucl. Phys. A 676 49 (2000)]. Reasonable agreement with available experimental data is obtained. Quadrupole moments of unstable nuclei including ¹⁰⁰Sn and ¹³²Sn are predicted. A nontrivial dependence of the quadrupole moments on the neutron excess is found which can be traced to the negative proton contributions.

Jun 3, 2012 by Theo theory 0

[paper] Quadrupole moments of spherical semi-magic nuclei within the self-consistent Theory of Finite Fermi Systems

Quadrupole moments of spherical semi-magic nuclei within the self-consistent Theory of Finite Fermi Systems

S.V. Tolokonnikov et al.

doi: 10.1140/epja/i2012-12070-1

The quadrupole moments of odd neighbors of semi-magic lead and tin isotopes and N=50, N=82 isotones are calculated within the self-consistent Theory of Finite Fermi Systems based on the Energy Density Functional by Fayans et al. Two sets of published functionals are used to estimate systematic errors of the present self-consistent approach. They differ by the spin-orbit and effective tensor force parameters. The functional DF3-a leads to quadrupole moments in reasonable agreement with the experimental ones for most, but not all, nuclei considered.

May 27, 2012 by Theo g factor 0

[paper] Is the 7/2₁^– Isomer State of ⁴³S Spherical?

Is the 7/2₁^– Isomer State of ⁴³S Spherical?

R. Chevrier et al.

doi: 10.1103/PhysRevLett.108.162501

We report on the spectroscopic quadrupole moment measurement of the 7/2₁^– isomeric state in ⁴³₁₆S₂₇ [E^*=320.5(5) keV, T_1/2=415(3) ns], using the time dependent perturbed angular distribution technique at the RIKEN RIBF facility. Our value, ∣Q_s∣=23(3) efm², is larger than that expected for a single-particle state. Shell model calculations using the modern SDPF-U interaction for this mass region reproduce remarkably well the measured ∣Q_s∣, and show that non-negligible correlations drive the isomeric state away from a purely spherical shape.

Apr 16, 2012 by Theo g factor 0

[paper] Quadrupole moments of collective structures up to spin ∼65ℏ in ¹⁵⁷Er and ¹⁵⁸Er: A challenge for understanding triaxiality in nuclei

Quadrupole moments of collective structures up to spin ∼65ℏ in ¹⁵⁷Er and ¹⁵⁸Er: A challenge for understanding triaxiality in nuclei

X. Wang et al.

doi: 10.1016/j.physletb.2011.07.007

The transition quadrupole moments, Q_t, of four weakly populated collective bands up to spin ∼65ℏ in ^157,158Er have been measured to be ∼11 eb demonstrating that these sequences are associated with large deformations. However, the data are inconsistent with calculated values from cranked Nilsson–Strutinsky calculations that predict the lowest energy triaxial shape to be associated with rotation about the short principal axis. The data appear to favor either a stable triaxial shape rotating about the intermediate axis or, alternatively, a triaxial shape with larger deformation rotating about the short axis. These new results challenge the present understanding of triaxiality in nuclei.

Jul 13, 2011 by Theo experiment g factor theory 0

[paper] Wigner Crystals of ²²⁹Th for Optical Excitation of the Nuclear Isomer

Wigner Crystals of ²²⁹Th for Optical Excitation of the Nuclear Isomer

C.J. Campbell et al.

doi: 10.1103/PhysRevLett.106.223001

We have produced laser-cooled Wigner crystals of ²²⁹Th³⁺ in a linear Paul trap. The magnetic dipole (A) and electric quadrupole (B) hyperfine constants for four low-lying electronic levels and the relative isotope shifts with respect to ²³²Th³⁺ for three low-lying optical transitions are measured. Using the hyperfine B constants in conjunction with prior atomic structure calculations, a new value of the spectroscopic nuclear electric quadrupole moment Q=3.11(16) eb is deduced. These results are a step towards optical excitation of the low-lying isomer level in the ²²⁹Th nucleus.

Jun 30, 2011 by Theo experiment g factor 0

[paper] Quadrupole moment measurements for strongly deformed bands in ^171,172Hf

Quadrupole moment measurements for strongly deformed bands in ^171,172Hf

S. Mukhopadhyay et al.

doi: 10.1103/PhysRevC.83.044311

A lifetime experiment, using the Doppler-shift attenuation method, has been performed at Gammasphere to measure the transition quadrupole moments Qt of strongly deformed bands in ¹⁷¹Hf and ¹⁷²Hf. The measured value of Q_t ~ 9.5 e b for the band labeled ED in ¹⁷¹Hf strongly supports the recent suggestion that this sequence and several structures with similar properties in neighboring Hf isotopes are associated with a near-prolate shape with a deformation enhanced relative to that of normal deformed structures. The measured values of Q_t ~ 14 e b for the bands labeled SD1 and SD3 in ¹⁷²Hf confirm that these sequences are associated with a prolate superdeformed shape, a property inferred in earlier work from other measured characteristics of the bands. Similar bands in ^173-175Hf are also likely to be associated with superdeformed shapes. The observations are in contrast to predictions of cranking calculations performed with the ultimate cranker code.

Apr 13, 2011 by Theo experiment 1

[paper] Nuclear charge radii and electromagnetic moments of radioactive scandium isotopes and isomers

Nuclear charge radii and electromagnetic moments of radioactive scandium isotopes and isomers

M. Avgoulea et al.

doi: 10.1088/0954-3899/38/2/025104

Collinear laser spectroscopy experiments with the Sc⁺ transition 3d4s ³D₂ → 3d4p ³F3 at λ = 363.1 nm were performed on the ^42–46Sc isotopic chain using an ion guide isotope separator with a cooler-buncher. Nuclear magnetic dipole and electric quadrupole moments as well as isotope shifts were determined from the hyperfine structure for five ground states and two isomers. Extensive multi-configurational Dirac–Fock calculations were performed in order to evaluate the specific mass-shift, MSMS, and field-shift, F, parameters which allowed evaluation of the charge radii trend of the Sc isotopic sequence. The charge radii obtained show systematics more like the Ti radii, which increase towards the neutron shell closure N = 20, than the symmetric parabolic curve for Ca. The changes in mean-square charge radii of the isomeric states relative to the ground states for ⁴⁴Sc and ⁴⁵Sc were also extracted. The charge radii difference between the ground and isomeric states of ⁴⁵Sc is in agreement with the deformation effect estimated from the B(E2) measurements but is smaller than the deformation extracted from the spectroscopic quadrupole moments.

Jan 5, 2011 by Theo experiment g factor 0

[paper] g factors of nuclear low-lying states: A covariant description

g factors of nuclear low-lying states: A covariant description

JiangMing Yao et al.

doi: 10.1007/s11433-010-4214-8

The g factors and spectroscopic quadrupole moments of low-lying excited states 2₁⁺, …, 8₁⁺ in ₂₄Mg are studied in a covariant density functional theory. The wave functions are constructed by configuration mixing of axially deformed mean-field states projected on good angular momentum. The mean-field states are obtained from the constraint relativistic point-coupling model plus BCS calculations using the PC-F1 parametrization for the particle-hole channel and a density-independent delta-force for the particle-particle channel. The available experimental g factor and spectroscopic quadrupole moment of 2₁/⁺ state are reproduced quite well. The angular momentum dependence of g factors and spectroscopic quadrupole moments, as well as the effects of pairing correlations are investigated

Dec 6, 2010 by Theo theory 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

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