theory

[paper] Microscopic description of ground state magnetic moment and low-lying magnetic dipole excitations in heavy odd-mass 181Ta nucleus

Microscopic description of ground state magnetic moment and low-lying magnetic dipole excitations in heavy odd-mass181Ta nucleus

E. Tabar et al.

doi: http://dx.doi.org/10.1142/S0218301316500531

The ground state magnetic moments and the low-lying magnetic dipole (Ml) transitions from the ground to excited states in heavy deformed odd-mass 181Ta have been microscopically investigated on the basis of the quasiparticle-phonon nuclear model (QPNM). The problem of the spurious state mixing in M1 excitations is overcome by a restoration method allowing a self-consistent determination of the separable effective restoration forces. Due to the self-consistency of the method, these effective forces contain no arbitrary parameters. The results of calculations are compared with the available experimental data, the agreement being reasonably satisfactory.

Jul 20, 2016 by theory 0

[paper] Infrared extrapolations of quadrupole moments and transitions

Infrared extrapolations of quadrupole moments and transitions

D. Odell et al.

doi: 10.1103/PhysRevC.93.044331

We study the convergence of bound-state quadrupole moments in finite harmonic oscillator spaces. We derive an expression for the infrared extrapolation for the quadrupole moment of a nucleus and benchmark our results using different model interactions for the deuteron. We find good agreement between the analytically derived and numerically obtained convergence behavior. We also derive an extrapolation formula for electric quadrupole transitions and find good agreement with the numerical calculation of a simple system.

May 16, 2016 by quadrupole theory 0

[preprint] Effective field theory for nuclear vibrations with quantified uncertainties

Effective field theory for nuclear vibrations with quantified uncertainties

E.A. Coello Pérez and T. Papenbrock

arXiv: 1510.02401

We develop an effective field theory (EFT) for nuclear vibrations. The key ingredients – quadrupole degrees of freedom, rotational invariance, and a breakdown scale around the three-phonon level – are taken from data. The EFT is developed for spectra and electromagnetic moments and transitions. We employ tools from Bayesian statistics for the quantification of theoretical uncertainties. The EFT consistently describes spectra and electromagnetic transitions for 62Ni, 98,100Ru, 106,108Pd, 110,112,114Cd, and 118,120,122Te within the theoretical uncertainties. This suggests that these nuclei can be viewed as anharmonic vibrators.

Nov 12, 2015 by theory 0

[Paper] Magnetic moments in odd-A Cd isotopes and coupling of particles with zero-point vibrations

Magnetic moments in odd-A Cd isotopes and coupling of particles with zero-point vibrations

S. Mishev and V. V. Voronov

DOI: 10.1103/PhysRevC.92.044329

Background: The coupling of the last nucleon with configurations in the ground state of the even-even core is known to augment the single quasiparticle fragmentation pattern. In a recent experimental study by Yordanov et al. the values of the magnetic dipole and electric quadrupole moments of the 11/2− state in a long chain of Cd isotopes were found to follow a simple trend which we try to explain by means of incorporating long-range correlations in the ground state.

Purpose: Our purpose is to study the influence of ground-state correlations (GSCs) on the magnetic moments and compare our results with the data for the odd-A Cd isotopes.

Method: In order to evaluate if the additional correlations have bearing on the magnetic moments we employ an extension to the quasiparticle-phonon model (QPM) which takes into account quasiparticle⊗phonon configurations in the ground state of the even-even core affecting the structure of the odd-A nucleus wave function.

Results: It is shown that the values for the magnetic moments which the applied QPM extension yields deviate further from the Schmidt values. The latter is in agreement with the measured values for the Cd isotopes.

Conclusions: The GSCs exert significant influence on the magnetic dipole moments and reveal a potential for reproducing the experimental values for the studied cadmium isotopes.

Oct 28, 2015 by g factor theory 0

[paper] Structural evolution in transitional nuclei of mass 82≤A≤132

Structural evolution in transitional nuclei of mass 82≤A≤132

M. Bhutan

doi: 10.1103/PhysRevC.92.034323

In this theoretical study, we report an investigation on the behavior of two-neutron separation energy, a differential variation of the nucleon separation energy, the nuclear charge radii, and the single-particle energy levels along the isotopic chains of transitional nuclei. We have used the relativistic mean-field formalism with NL3 and NL3* forces for this present analysis. The study refers to the even-even nuclei such as Zr, Mo, Ru, and Pd for N=42−86, where a rich collective phenomena such as proton radioactivity, cluster or nucleus radioactivity, exotic shapes, island of inversion, etc. are observed. We found that there are few nonmonotonic aspects over the isotopic chain, which are correlated with the structural properties such as shell/subshell closures, the shape transition, clustering, magicity, etc. In addition to these, we have shown the internal configuration of these nuclei to get a further insight into the reason for these discrepancies.

Oct 3, 2015 by radii theory 0

[paper] The energy-weighted sum rule and the nuclear radius

The energy-weighted sum rule and the nuclear radius

Hans Peter Schröder

doi: 10.1140/epja/i2015-15109-9

The energy-weighted integrated cross-section for photon absorption –known as sum rule σ−1 — is under certain conditions proportional to the mean square nuclear radius (Levinger, Bethe (Phys. Rev. 78, 115 (1950))). Due to the energy weight factor the low-energy absorption components are emphasized and the dipole transitions in the region of giant resonances contribute enhanced at σ−1 . Thus, the cross-section of the full interaction can be replaced in good approximation by the dipole cross-section. Under these aspects, we have calculated σ−1 and the radii of various gg-nuclei. For our purpose, we have chosen a simple shell model where the integrals can be solved analytically, and the contributions of uncorrelated functions and correlation corrections can be shown explicitly. The mean square radius as a function of σ−1 differs by a factor of 1.5/0.87 from the previous result of Levinger and Kent (Phys. Rev. 95, 418 (1954)) without correlation corrections. Plotting the function of the correlation corrections g(A) and the uncorrelated function f(A) as a ratio it shows that g(A)/f(A) tends towards a limit. Finally, our results for the radii of gg-nuclei are in good agreement with recent experiments (I. Angeli, K.P. Marinova, At. Data Nucl. Data Tables 99, 69 (2013)).

Oct 2, 2015 by radii theory 0

[paper] Magnetic moments of the low-lying JP = 1/2–, 3/2– Λ resonances within the framework of the chiral quark model

Magnetic moments of the low-lying JP = 1/2–, 3/2– Λ resonances within the framework of the chiral quark model

A. Martinez Torres et al

doi: 10.1140/epja/i2012-12185-3

The magnetic moments of the low-lying spin-parity JP = 1/2–, 3/2– Λ resonances, like, for example, Λ(1405)1/2–, Λ(1520) 3/2–, as well as their transition magnetic moments, are calculated using the chiral quark model. The results found are compared with those obtained from the nonrelativistic quark model and those of unitary chiral theories, where some of these states are generated through the dynamics of two hadron coupled channels and their unitarization.

Jan 6, 2013 by theory 0

[paper] Deuteron magnetic quadrupole moment from chiral effective field theory

Deuteron magnetic quadrupole moment from chiral effective field theory

C.-P. Liu et al.

doi: 10.1016/j.physletb.2012.06.024

We calculate the magnetic quadrupole moment (MQM) of the deuteron at leading order in the systematic expansion provided by chiral effective field theory. We take into account parity (P) and time-reversal (T) violation which, at the quark–gluon level, results from the QCD vacuum angle and dimension-six operators that originate from physics beyond the Standard Model. We show that the deuteron MQM can be expressed in terms of five low-energy constants that appear in the P- and T-violating nuclear potential and electromagnetic current, four of which also contribute to the electric dipole moments of light nuclei. We conclude that the deuteron MQM has an enhanced sensitivity to the QCD vacuum angle and that its measurement would be complementary to the proposed measurements of light-nuclear EDMs.

Jul 18, 2012 by theory 0

[paper] Magnetic moments of K isomers as indicators of octupole collectivity

Magnetic moments of K isomers as indicators of octupole collectivity

N. Minkov and P. M. Walker

doi: 10.1140/epja/i2012-12080-y

The relation between the quadrupole-octupole deformation and the structure of high-K isomers in heavy even-even nuclei is studied through a reflection asymmetric deformed shell model including a BCS procedure with constant pairing interaction. Two-quasiparticle states with Kπ=4−, 5−, 6−, 6+ and 7− are considered in the region of actinide nuclei (U, Pu and Cm) and rare-earth nuclei (Nd, Sm and Gd). The behaviour of two-quasiparticle energies and magnetic dipole moments of these configurations is examined over a wide range in the plane of quadrupole and octupole deformations (&betal2 and β3. In all considered actinide nuclei, the calculations show that there is pronounced sensitivity of the magnetic moments to the octupole deformation. In the rare-earth nuclei, the calculations for 154,156Gd show stronger sensitivity of the magnetic moment to the octupole deformation than in the other considered cases.

Jun 10, 2012 by theory 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 theory 0

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