Theo

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

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

R. Chevrier et al.

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] Direct Measurement of the Proton Magnetic Moment

Direct Measurement of the Proton Magnetic Moment

J. DiSciacca and G. Gabrielse

doi: 10.1103/PhysRevLett.108.153001

The proton magnetic moment in nuclear magnetons is measured to be μ_p/μ_N≡g/2=2.792 846±0.000 007, a 2.5 parts per million uncertainty. The direct determination, using a single proton in a Penning trap, demonstrates the first method that should work as well with an antiproton (p̅ ) as with a proton (p). This opens the way to measuring the p̅ magnetic moment (whose uncertainty has essentially not been reduced for 20 years) at least 103 times more precisely.

Apr 10, 2012 by Theo g factor 0

[Conference paper] Physics highlights from laser spectroscopy at the IGISOL

Physics highlights from laser spectroscopy at the IGISOL

D.H. Forest and B. Cheal

doi: 10.1007/s10751-012-0620-9

Laser spectroscopy provides model-independent access to a variety of radioactive nuclear ground state and isomeric state properties. These include the nuclear moments, changes in mean-square charge radii, and direct measurements of the nuclear spin. At the IGISOL laboratory, the collinear laser spectroscopy programme is able to access cases, such as refractory elements and short-lived states, not available at conventional facilities. A summary of physics highlights is presented here.

Mar 30, 2012 by Theo g factor 0

[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

An exciting day for magnetic moments.info

Hello All,

For us, this is a great day!

The website of the database has been upgraded together with the database itself. There are new exciting features:

The database is upgraded and contains all data up to Stone’s compilation (2005)
DOI numbers are featured in all data (where the corresponding reference features a DOI number)
The database has been re-written from scratch in PHP and MySQL, instead of plain HTML
The server is programmed to respond to searches by Z, A or combination of them
You can probe isobaric or isotopic data for comparison or trending
Redesigned CSS to support the new HTML interface. Still needs some work however

More features / improvements to come:

New data will be added from recent references
The core engine will be improved in search speed
Most likely we will move or get mirrored to a University-based server.

In case you would like to contribute your new data please email us. The philosophy of this database is similar to that of XUNDL: unevaluated data, but fast-appearing online to help the community.

Thanks for the support

Mar 6, 2012 by Theo g factor 2

[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] Nuclear Charge Radii of ^21-32Mg

Nuclear Charge Radii of ^21-32Mg

D.T. Yordanov et al.

doi: 10.1103/PhysRevLett.108.042504

Charge radii of all magnesium isotopes in the sd shell have been measured, revealing evolution of the nuclear shape throughout two prominent regions of assumed deformation centered on ²⁴Mg and ³²Mg. A striking correspondence is found between the nuclear charge radius and the neutron shell structure. The importance of cluster configurations towards N=8 and collectivity near N=20 is discussed in the framework of the fermionic molecular dynamics model. These essential results have been made possible by the first application of laser-induced nuclear orientation for isotope shift measurements.

Jan 26, 2012 by Theo g factor 0

The importance of magnetic moments to nuclear structure – a comment by N.D. Cook

I have received the following as a comment to the website. I strongly believe this is an important advocate of our website and motivation behind organizing it, as well as a good read for all people in the field of nuclear physics. Here it is:

Dear Theo,

I have previously relied on Nick Stone’s compilation, but I am happy to have found your website with active updating of nuclear magnetic moments. This is why the internet is so wonderful, so I wish you luck in drawing attention to this valuable resource!
Maybe anyone interested in magnetic moments already understands this, but what I think is still missing from your website is indication of the importance of specifically the magnetic moments for a proper understanding of nuclear structure.

On the one hand, the textbooks typically show the Schmidt Lines, together with data points indicating that most experimental values lie between the upper and lower values. Already by the early 1950s, the Schmidt lines clearly indicated that the independent-particle model was more-or-less valid, but there has been surprisingly little progress since then. Because the modern experimental data are precise up to 7 or 8 digits and classical electromagnetic theory is well understood, explanation of nuclear magnetic moments SHOULD be (but is not yet) an area where discrepancies between experiment and theory might be discussed with some clarity!

On the other hand, theorists who calculate nuclear magnetic moments typically use model parameters that are adjusted to reproduce the experimental data. Adjusting the parameters of the nuclear models is entirely normal practice, but such modeling gives the impression that the magnetic moments are understood quantitatively, whereas the truth is considerably less optimistic. That “hard reality” is not often acknowledged, I would say, but last year a Chinese physics journal, SCIENCE CHINA, was rather straight-forward in stating the continuing problems in explaining nuclear magnetic moments.

http://esciencenews.com/articles/2010/12/23/nuclear.magnetic.moments

In explaining why they were to publish a Special Issue devoted to nuclear moments, the Editors noted that:
“the extension of these [nuclear] models to the study of nuclear magnetic moments is quite limited and unsatisfactory. The magnetic dipole moments of most atomic nuclei throughout the periodic table still remain unexplained and the under-lying physics mechanism is not fully understood….”

And, among the invited reviews of theoretical work that were eventually published, Akito Arima went through the usual explanation of the Schmidt lines, and even cited the good agreement between experiment and theory for a few selected nuclei from his own work published in…. 1954!

I would guess that you are not interested in getting into abstruse theoretical discussions on your web-site, but I think some indication of the current lack of theoretical understanding of nuclear magnetic moments would indicate why nuclear moments are indeed an important topic!

Cheers
Norman

N.D.Cook

Jan 24, 2012 by Theo g factor 0

The database is now complete!

Folks,

This is exciting times for the database we’ve been trying to put online during the past 2 years. In the process, we’ve had severe failures, major redesigns and several updates. Nevertheless, our efforts are proven fruitful and we are now pleased to announce the complete set of nuclear magnetic dipole and electric quadrupole moments to the community. As a bonus, magnetic moments of elementary particles are now featured in the database. Also, we have tried to modernize the frontend by adding an alternative view, using a helix-like ladder that symbolizes both the expansion of our site and the future of nuclear data collection and archiving.

Our database can be directly found in this link: http://magneticmoments.info/data

The data have been collected from fully electronic and printed sources. Prof. N.J. Stone’s milestone paper was used as the major source, but our database is extended gradually to include more information, such as DOI keys and non-evaluated data as they appear in this blog, and elsewhere, for the convenience of the fellow researchers.

We welcome comments, corrections, suggestions and of course DONATIONS 🙂 This server is a fully private project without any financial support other than our pocket. So, if you think it’s interesting, send us an email and we can tell you how you can help our site grow. In any case, thanks for visiting!

Jan 8, 2012 by Theo g factor 2

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