Theo

1228 isotopes, 5800 entries later

Last Friday, 28.10, was a National Holiday here in Greece, our OXI! day (“No!” day in english), the 76th anniversary of the beginning of WWII in Greece, after Italy’s attack on the NW border with Albania. It is always a nice holiday as kids and grown ups don’t go to school and people grab the opportunty to do something nice, weather permitted, which is more or less the truth since October has been generous with sunlight and medium temperatures the recent years.

For my account, I chose to revisit a favorite land, an exciting land, the land of isotopes. You might know already or have concluded from visiting this page that I maintain a database of nuclear electromagnetic moments, which is rather unique worldwide and has been an integral part of the IAEA Nuclear Data Section for over a year now (this is the moment you should appllaud people!). I spent my OXI break updating the database, which at the beginning of the week seemed easy, but in the end resulted in a very difficult task as I have found several typos, mistakes in the values and losses of format integrity inherited from previous printed compilations. The proofing is a very difficult job and one has to do it carefully at the very beginning, else there is always the risk to transmit -eternally- wrong information. And I wouldn’t like to think I have the wrong value of the proton magnetic moment when I get my next MRI exam…

All in all, the database has now 1228 isotopes spanning a set of 5800 entries of magnetic dipole and electric quadrupole moments. Both numbers are larger if you include the nuclear charge radii that now exist only in the development server together with nuclear masses and X-ray data. This version will be updated fully after the AME2016 will be published, word says some time in this coming December.

Despite the “self-confinement” on a chair inside a room with tons of tea and coffee, my OXI day weekend has been both fruitful and joyous. But next time I will pick a different destination 😉

Oct 31, 2016 by g factor 0

[Paper] Sensitivities and correlations of nuclear structure observables emerging from chiral interactions

Sensitivities and correlations of nuclear structure observables emerging from chiral interactions

Angelo Calci and Robert Roth

doi: 10.1103/PhysRevC.94.014322

Abstract

Starting from a set of different two- and three-nucleon interactions from chiral effective field theory, we use the importance-truncated no-core shell model for ab initio calculations of excitation energies as well as electric quadrupole (E2) and magnetic dipole (M1) moments and transition strengths for selected p-shell nuclei. We explore the sensitivity of the excitation energies to the chiral interactions as a first step towards and systematic uncertainty propagation from chiral inputs to nuclear structure observables. The uncertainty band spanned by the different chiral interactions is typically in agreement with experimental excitation energies, but we also identify observables with notable discrepancies beyond the theoretical uncertainty that reveal insufficiencies in the chiral interactions. For electromagnetic observables we identify correlations among pairs of E2 or M1 observables based on the ab initio calculations for the different interactions. We find extremely robust correlations for E2 observables and illustrate how these correlations can be used to predict one observable based on an experimental datum for the second observable. In this way we circumvent convergence issues and arrive at far more accurate results than any direct ab initio calculation. A prime example for this approach is the quadrupole moment of the first 2+ state in C12, which is predicted with an drastically improved accuracy.

Jul 31, 2016 by theory 0

[Paper] Radii and Binding Energies in Oxygen Isotopes: A Challenge for Nuclear Forces

Radii and Binding Energies in Oxygen Isotopes: A Challenge for Nuclear Forces

V. Lapoux et al.
doi: 10.1103/PhysRevLett.117.052501

We present a systematic study of both nuclear radii and binding energies in (even) oxygen isotopes from the valley of stability to the neutron drip line. Both charge and matter radii are compared to state-of-the-art ab initio calculations along with binding energy systematics. Experimental matter radii are obtained through a complete evaluation of the available elastic proton scattering data of oxygen isotopes. We show that, in spite of a good reproduction of binding energies, ab initio calculations with conventional nuclear interactions derived within chiral effective field theory fail to provide a realistic description of charge and matter radii. A novel version of two- and three-nucleon forces leads to considerable improvement of the simultaneous description of the three observables for stable isotopes but shows deficiencies for the most neutron-rich systems. Thus, crucial challenges related to the development of nuclear interactions remain.

Jul 29, 2016 by radii theory 0

An update to the nuclear moments database

The nuclear moments database is sponsored and hosted by the IAEA Nuclear Data Section.
See the latest official release here:
http://www-nds.iaea.org/nuclearmoments

This is a major update with cutoff date 30.06.2016. The next is scheduled for 30.09.2016.

On the parallel, on the development server (always on beta status) http://data.magneticmoments.info
a new database is being tested that additionally includes nuclear charge radii and nuclear masses (in fact mass excess values).
This database is currently in sync with the IAEA servers, but will eventually branch out (early next year).

My recommendation is to follow the official releases on IAEA web if you want to use it in a paper (please cite the database using the citations listed in the server). If you can’t wait for the official release, try the development server, where more features are and will be available as the site expands.

Typos, comments or missing values? PLEASE let me know about it (thanks in advance!)
The blog is also there for more resources http://magneticmoments.info/wp

Jul 29, 2016 by g factor 0

[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

An update of the nuclear moments update: masses and charge radii

For those of you who are following my blog or twitter feed, what I am about to say is not quite new. I have already made a comment a couple of weeks ago regarding the last update of the database I administer. The database contains non-evaluated, experimentally deduced values of nuclear magnetic dipole and electric quadrupole moments. The official release of the database is hosted on IAEA servers and they are responsible for the dissemination of the information included to the world’s nuclear community. However, I keep a test server available for updates and testing new ideas before they appear on the IAEA’s website. This URL is http://magneticmoments.info/data

As I said earlier, a couple of weeks ago I have managed to find the time and upgrade the database with two important observables that people have requested in the recent past. The first one is masses, while the second one is nuclear charge radii. The former is listed in each isotope selected in the database in the form of mass excess Δm (=mass-A). Please notice I do not provide the whole table maintained by the Chinese colleagues (latest AME2012). Rather, I use it as an associate value to the spectroscopic values included when an isotope is selected.

The nuclear charge radii on the other hand is a new addition to the database and I intend to keep updating regardless the official releases (in print format) by IAEA or any other source. The radii are important structure information and as such they will be treated with extra care during each upgrade.

Besides these two extensive updates, lifetimes, spins and parities are slowly being synced with the evaluated data existing in the ENSDF.

You spot a problem or have something to say about the database, please let me know.

May 25, 2016 by g factor 0

[paper] Magnetic moment of the 13/2+ isomeric state in 69Cu: Spin alignment in the one-nucleon removal reaction

Magnetic moment of the 13/2+ isomeric state in 69Cu: Spin alignment in the one-nucleon removal reaction

A. Kusoglu et al.

doi: http://dx.doi.org/10.1103/PhysRevC.93.054313

We report on a new measurement of the g factor of the (13/2+) isomeric state in the neutron-rich nucleus 69Cu. This study demonstrates the possibility of obtaining considerable nuclear spin alignment for multi-quasiparticle states in single-nucleon removal reactions. The time-dependent perturbed angular distribution (TDPAD) method was used to extract the gyromagnetic factor of the (13/2+) [T½=351(14) ns] isomeric state of 69Cu. Its g factor was obtained as g(13/2+)=0.248(9). The experimentally observed spin alignment for the state of interest was deduced as A=−3.3(9)%.

May 16, 2016 by experiment 0

[paper] Isomer Shift and Magnetic Moment of the Long-Lived ½+ Isomer in 79Zn: Signature of Shape Coexistence near 78Ni

Isomer Shift and Magnetic Moment of the Long-Lived ½+ Isomer in 79Zn: Signature of Shape Coexistence near 78Ni

X.F. Yang et al.

doi: 10.1103/PhysRevLett.116.182502

Collinear laser spectroscopy is performed on the 79Zn isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life is confirmed, and the nuclear spins and moments of the ground and isomeric states in 79Zn, as well as the isomer shift are measured. From the observed hyperfine structures, spins I=9/2 and I=½ are firmly assigned to the ground and isomeric states. The magnetic moment μ(79Zn)=-1.1866(10)μN, confirms the spin-parity I=9/2+ with a νg9/2-1  shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment μ(79mZn)=-1.0180(12)μN  supports a positive parity for the isomer, with a wave function dominated by a 2h-1p neutron excitation across the N=50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state, δ2>79,79m=+0.204(6) fm2, providing first evidence of shape coexistence.

May 16, 2016 by g factor 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

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