PRC

[paper] First g(2+) measurement on neutron-rich ⁷²Zn, and the high-velocity transient field technique for radioactive heavy-ion beams

First g(2+) measurement on neutron-rich ⁷²Zn, and the high-velocity transient field technique for radioactive heavy-ion beams

E. Fiori et al.

doi: 10.1103/PhysRevC.85.034334

The high-velocity transient-field (HVTF) technique was used to measure the g factor of the 2⁺ state of ⁷²Zn produced as a radioactive beam. The transient-field strength was probed at high velocity in ferromagnetic iron and gadolinium hosts using ⁷⁶Ge beams. The potential of the HVTF method is demonstrated and the difficulties that need to be overcome for a reliable use of the TF technique with high-Z, high-velocity radioactive beams are revealed. The polarization of K-shell vacancies at high velocity, which shows more than an order of magnitude difference between Z=20 and Z=30 is discussed. The g-factor measurement hints at the theoretically predicted transition in the structure of the Zn isotopes near N=40

Mar 29, 2012 by Theo g factor 0

[paper] g factor of the 2₁⁺ state of ¹⁶⁸Hf

g factor of the 2₁⁺ state of ¹⁶⁸Hf

A. Wolf et al.

doi: 10.1103/PhysRevC.85.037304

The g factor of the 2₁⁺ state of ¹⁶⁸Hf was measured using the perturbed angular correlation technique in a static external magnetic field. The result, g(2₁⁺)=0.17(3), is discussed in relation to the systematics of the previously reported g factors in the Hf isotopes and compared to the predictions of several models. An interesting outcome of the analysis presented in this paper has to do with the relatively small result for the g factor. This indicates that in the Hf isotopes, a minimum in the g(2₁⁺) dependence on N occurs at N≤98 and not at midshell, as expected from IBA-2 or large-scale shell-model calculations. The pairing plus quadrupole model of Kumar and Baranger predicts a minimum at N=98 and gives the best description of the experimental data. The present result clearly shows the importance of g-factor measurements in “fine-tuning” among different models.

Mar 19, 2012 by Theo 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] First g-factor measurements of the 2₁⁺ and the 4₁⁺ states of radioactive ¹⁰⁰Pd

First g-factor measurements of the 2₁⁺ and the 4₁⁺ states of radioactive ¹⁰⁰Pd

D.A. Torres et al.

doi: 10.1103/PhysRevC.84.044327

The g factors of the first 2⁺ and 4⁺ states of the radioactive ¹⁰⁰Pd nucleus have been investigated for the first time, using an α-particle transfer reaction from ¹²C to ⁹⁶Ru. The transient magnetic field technique in inverse kinematics was used. The ¹⁰⁰₄₆Pd₅₄ nucleus is a suitable candidate for studying single-particle proton and neutron effects in the nuclear wave functions near the N=Z=50 shell closures. The results are discussed within the frameworks of both large-scale shell-model calculations and collective-model predictions.

Oct 25, 2011 by Theo g factor 0

[paper] In-source laser spectroscopy of ^75,77,78Cu: Direct evidence for a change in the quasiparticle energy sequence in ^75,77Cu and an absence of longer-lived isomers in ⁷⁸Cu

In-source laser spectroscopy of ^75,77,78Cu: Direct evidence for a change in the quasiparticle energy sequence in ^75,77Cu and an absence of longer-lived isomers in ⁷⁸Cu

U. Köster et al.

doi: 10.1103/PhysRevC.84.034320

This paper describes measurements on the isotopes ^75,77,78Cu by the technique of in-source laser spectroscopy, at the ISOLDE facility, CERN. The role of this technique is briefly discussed in the context of this and other, higher resolution, methods applied to copper isotopes in the range ⁵⁷⁻⁷⁸Cu. The data, analyzed in comparison with previous results on the lighter isotopes ^59,63Cu, establish the ground-state nuclear spin of ^75,77Cu as 5/2 and yield their magnetic dipole moments as +1.01(5)μ_N and +1.61(5)μ_N, respectively. The results on ⁷⁸Cu show no evidence for long-lived isomerism at this mass number and are consistent with a spin in the range 3–6 and moment of 0.0(4) μ_N.

Sep 29, 2011 by Theo g factor 0

[paper] Gyromagnetic factors in ^144-150Nd

Gyromagnetic factors in ^144-150Nd

A. Giannatiempo

doi: 10.1103/PhysRevC.84.034319

The U(5) to SU(3) evolution of the nuclear structure in the even ^144-156Nd isotopes has been investigated in the framework of the interacting boson approximation (IBA-2) model, taking into account the effect of the partial Z=64 subshell closure on the structure of the states of a collective nature. The analysis, which led to a satisfactory description of excitation energy patterns, quadrupole moments, and decay properties of the states (even when important M1 components were present in the transitions), is extended to the available data on g factors, in ^144-150Nd. Their values are reasonably reproduced by the calculations.

Sep 22, 2011 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

[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 spins, magnetic moments, and quadrupole moments of Cu isotopes from N=28 to N=46: Probes for core polarization effects

Nuclear spins, magnetic moments, and quadrupole moments of Cu isotopes from N=28 to N=46: Probes for core polarization effects

P. Vingerhoets et al.

doi: 10.1103/PhysRevC.82.064311

Measurements of the ground-state nuclear spins and magnetic and quadrupole moments of the copper isotopes from ⁶¹Cu up to ⁷⁵Cu are reported. The experiments were performed at the CERN online isotope mass separator (ISOLDE) facility, using the technique of collinear laser spectroscopy. The trend in the magnetic moments between the N=28 and N=50 shell closures is reasonably reproduced by large-scale shell-model calculations starting from a ⁵⁶Ni core. The quadrupole moments reveal a strong polarization of the underlying Ni core when the neutron shell is opened, which is, however, strongly reduced at N=40 due to the parity change between the pf and g orbits. No enhanced core polarization is seen beyond N=40. Deviations between measured and calculated moments are attributed to the softness of the ⁵⁶Ni core and weakening of the Z=28 and N=28 shell gaps.

Dec 17, 2010 by Theo experiment g factor 0

[paper] Shape coexistence near the N=38 shell gap: Magnetic moment of the 981.6 keV J^π=8⁺ level in ⁷²As

Shape coexistence near the N=38 shell gap: Magnetic moment of the 981.6 keV J^π=8⁺ level in ⁷²As

D. Pantelică et al.

doi: 10.1103/PhysRevC.82.044313

We report on the first determination of the magnetic moment of the 981.1 keV, J^π=8⁺ level in ⁷²As, a nucleus that belongs to the A≈70 mass region dominated by rapidly changing deformations and shapes. The 8⁺ level is the bandhead of a collective sequence of positive parity levels coexisting with low-spin and medium-spin spherical shell-model states. The magnetic moment was measured by the time-integral perturbed angular distributions method to be μ=-(4.272±0.280)μ_N. This value is in disagreement with the presumed [π(1g_9/2),ν(1g_9/2)] configuration and points to a more complex configuration involving two neutrons in the 1g_9/2 orbital.

Oct 20, 2010 by Theo experiment g factor theory 0

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