experiment

[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] 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 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] g Factor of Hydrogenlike ²⁸Si¹³⁺

g Factor of Hydrogenlike ²⁸Si¹³⁺

S. Sturm et al.

doi: 10.1103/PhysRevLett.107.023002

We determined the experimental value of the g factor of the electron bound in hydrogenlike ²⁸Si¹³⁺ by using a single ion confined in a cylindrical Penning trap. From the ratio of the ion’s cyclotron frequency and the induced spin flip frequency, we obtain g=1.995 348 958 7(5)(3)(8). It is in excellent agreement with the state-of-the-art theoretical value of 1.995 348 958 0(17), which includes QED contributions up to the two-loop level of the order of (Zα)2 and (Zα)4 and represents a stringent test of bound-state quantum electrodynamics calculations.

Jul 7, 2011 by Theo experiment g factor 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] 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

[paper] Magnetic moment of ¹⁰⁴Ag^m and the hyperfine magnetic field of Ag in Fe using nuclear magnetic resonance on oriented nuclei

Magnetic moment of ¹⁰⁴Ag^m and the hyperfine magnetic field of Ag in Fe using nuclear magnetic resonance on oriented nuclei

V.V. Golovko et al.

doi: 10.1103/PhysRevC.81.054323

Nuclear magnetic resonance (NMR/ON) measurements with β- and γ-ray detection have been performed on oriented ¹⁰⁴Ag^g,m nuclei with the NICOLE ³He-⁴He dilution refrigerator setup at ISOLDE/CERN. For ¹⁰⁴Ag^g (I^π=5⁺) the γ-NMR/ON resonance signal was found at ν=266.70(5) MHz. Combining this result with the known magnetic moment for this isotope, the magnetic hyperfine field of Ag impurities in an Fe host at low temperature (<1 K) is found to be |B_hf(AgFe)|=44.709(35) T. A detailed analysis of other relevant data available in the literature yields three more values for this hyperfine field. Averaging all four values yields a new and precise value for the hyperfine field of Ag in Fe; that is, |B_hf(AgFe)|=44.692(30) T. For ¹⁰⁴Ag^m (I^π=2⁺), the anisotropy of the β particles provided the NMR/ON resonance signal at ν=627.7(4) MHz. Using the new value for the hyperfine field of Ag in Fe, this frequency corresponds to the magnetic moment μ(^104mAg)=+3.691(3) μ_N, which is significantly more precise than previous results. The magnetic moments of the even-A ^102-110Ag isotopes are discussed in view of the competition between the (πg_9/2)^7/2+-3(νd_5/2νg_7/2)^5/2+ and the (πg_9/2)^9/2+-3(νd_5/2νg_7/2)^5/2+ configurations. The magnetic moments of the ground and isomeric states of ¹⁰⁴Ag can be explained by an almost complete mixing of these two configurations.

May 28, 2010 by Theo experiment g factor theory 0

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