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[preprint] Populating Low-Spin States in Radioactive Nuclei to Measure Magnetic Moments Using the Transient Field Technique

Populating Low-Spin States in Radioactive Nuclei to Measure Magnetic Moments Using the Transient Field Technique

D.A. Torres and F. Ramírez

The experimental study of magnetic moments for nuclear states near the ground state, I≥2, provides a powerful tool to test nuclear structure models. The study of magnetic moments in nuclei far away from the stability line is the next frontier in such studies. Two techniques have been utilized to populated low-spin states in radioactive nuclei: coulomb excitation reactions using radioactive nuclei, and the transfer of α particles to stable beams to populate low spin states in radioactive nuclei. A presentations of these two techniques, along with the experimental challenges presented for future uses with nuclei far away from the stability line, will be presented.

Jan 17, 2016 by Theo experiment g factor 0

[Paper] Investigation into the semimagic nature of the tin isotopes through electromagnetic moments

Investigation into the semimagic nature of the tin isotopes through electromagnetic moments

J.M. Allmond et al.

DOI: 10.1103/PhysRevC.92.041303

A complete set of electromagnetic moments, B(E2;0⁺₁→2⁺₁),Q(2⁺₁), and g(2⁺₁), have been measured from Coulomb excitation of semi magic ^{112,114,116,118,120,122,124}Sn (Z=50) on natural carbon and titanium targets. The magnitude of the B(E2) values, measured to a precision of ∼4%, disagree with a recent lifetime study [Phys. Lett. B 695, 110 (2011)] that employed the Doppler-shift attenuation method. The B(E2) values show an overall enhancement compared with recent theoretical calculations and a clear asymmetry about midshell, contrary to naive expectations. A new static electric quadrupole moment, Q(2⁺₁), has been measured for ¹¹⁴Sn. The static quadrupole moments are generally consistent with zero but reveal an enhancement near midshell; this had not been previously observed. The magnetic dipole moments are consistent with previous measurements and show a near monotonic decrease in value with neutron number. The g-factor measurements in ^112,114Sn establish the recoil-in-vacuum method for states with τ∼0.5 ps and hence demonstrate that this method can be used for future g-factor measurements on proton-rich isotopes toward ¹⁰⁰Sn. Current theory calculations fail to reproduce the electromagnetic moments of the tin isotopes. The role of 2p-2h and 4p-4h intruders, which are lowest in energy at midshell and outside of current model spaces, needs to be investigated in the future.

Oct 19, 2015 by Theo g factor quadrupole 0

[paper] Structure of the Sr-Zr isotopes near and at the magic N=50 shell from g-factor and lifetime measurements in⁸⁸₄₀Zr and ^84,86,88₃₈Sr

Structure of the Sr-Zr isotopes near and at the magic N=50 shell from g-factor and lifetime measurements in⁸⁸₄₀Zr and ^84,86,88₃₈Sr

G. Kumbartzki et al.

doi: 10.1103/PhysRevC.85.044322

Background: The evolution of and interplay between single-particle and collective excitations in the 40 ⩽N⩽ 50 range for 38Sr and 40Zr isotopes have been studied.

Purpose: Measurement of the g factor of the 2₁⁺ and 4₁⁺ states in radioactive ⁸⁸Zr while simultaneously remeasuring the g(2₁⁺) factors in the Sr isotopes and extention of the measurements to higher energy states in the Sr isotopes. Lifetimes of states in these nuclei are determined.

Methods: The transient field technique in inverse kinematics and line-shape analysis using the Doppler-shift attenuation method are applied. The ⁸⁸Zr nuclei were produced by the transfer of an α particle from the ¹²C nuclei of the target to ⁸⁴Sr nuclei in the beam. The excited states in the stable ⁸⁴Sr isotopes were simultaneously populated via Coulomb excitation by ¹²C in the same target. Coulomb excitation measurements on ^86,88Sr were carried out with the same apparatus.

Results: The resulting g factors and B(E2) values of these nuclei reveal similarities between the two chains of Zr and Sr isotopes. Large-scale shell-model calculations were performed within the p_3/2, f_5/2, p_1/2, g_9/2 orbital space for both protons and neutrons and yielded results in agreement with the experimental data.

Conclusions: In this paper the magnetic moments and lifetimes of several low-lying states in ⁸⁸Zr and ^84,86,88Sr have been measured and compared to large-scale shell-model calculations.

Apr 30, 2012 by Theo experiment g factor 0

[paper] Measurement of the ⁹⁶Ru g(4₁⁺) factor and its nuclear structure interpretation

Measurement of the ⁹⁶Ru g(4₁⁺) factor and its nuclear structure interpretation

D.A. Torres et al.

doi: 10.1103/PhysRevC.85.017305

Background: The experimental study of g(I>2) factors of nuclear states can provide information about the evolution of collectivity in certain regions of the nuclear chart, and assist in obtaining a microscopic description of the nuclear wave functions. The measurements and explanations of g(I>2) factors are still a challenge for experiments and theory.

Purpose: Measurement of the g(2₁⁺) and g(4₁⁺) factors, the latter for the first time, in the ⁹⁶₄₄Ru nucleus. Comparison of the experimental results with calculations using the shell model and collective models.

Methods: The experiments made use of the transient field technique, using a Coulomb-excitation reaction in inverse kinematics. Large scale shell model calculations were performed; comparisons with previous theoretical predictions, using the tidal-wave model and the hydrodynamical model, were carried out.

Results: The values of g(2₁⁺)=+0.46(2) and g(4₁⁺)=+0.58(8) were experimentally obtained. While the g(2₁⁺) value agrees with the hydrodynamical model prediction of g=Z/A=+0.46, the g(4₁⁺) is in agreement with the shell model predictions. The trend of the experimental g factors, as a function of nuclear spin, is not reproduced by the theoretical models discussed.

Conclusions: Measurements of g(2₁⁺) and g(4₁⁺) in ⁹⁶Ru were performed. Further theoretical efforts are necessary to explain the trend of the g factors as a function of nuclear spin for the ⁹⁶Ru nucleus. Future measurements of g(4₁⁺) should reduce the uncertainty of the result.

Jan 30, 2012 by Theo g factor 0

[paper] Magnetic moments of the first excited 2⁺ states in the semi-magic ^{112,114,116,122,124}Sn isotopes

Magnetic moments of the first excited 2⁺ states in the semi-magic ^{112,114,116,122,124}Sn isotopes

J. Walker et al.

doi: 10.1103/PhysRevC.84.014319

The g factors of the first excited 2⁺ states in the ^{112,114,116,122,124}Sn isotopes have been measured with high accuracy using the transient field technique in combination with Coulomb excitation in inverse kinematics. The experimental results are discussed in a qualitative way on the basis of empirical single-particle g factors of the relevant proton and neutron orbitals and are compared to a number of different theoretical calculations. The results are found to be best described by shell-model calculations in an extended configuration space. Clear evidence for the contribution of neutron pair excitations from the 1d_3/2 to the 0h_11/2 orbital to the wave function of the 2₁⁺ state in ^122,124Sn has been obtained.

Jul 19, 2011 by Theo experiment g factor 0

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