CM on Evaluation of Nuclear Moments

16 Dec 2025, 09:00 → 19 Dec 2025, 17:00 Europe/Zurich

M0E16 (Vienna)

Paraskevi DIMITRIOU (International Atomic Energy Agency)

A meeting will be held to evaluate the current status of the IAEA Nuclear Moments database (https://nds.iaea.org/nuclearmoments/), review recent measurements and advances in data analysis and evaluation methodologies, recommend best practices, and outline a work plan to ensure the database’s maintenance and future development.

Previous meeting summary report: CM on Evaluation of Nuclear Moments, 2017

Tuesday 16 December

Welcome

Presentations I

1 Introduction: motivation and goals of meeting

Speaker: Dr Paraskevi DIMITRIOU (International Atomic Energy Agency)

2 Measurement and evaluation of moments of short-lived states

I will review some of the methods to measure the magnetic moments of short-lived excited states. The challenges of the measurements and consequent challenges to evaluate and compile the data will be discussed.

Speaker: Andrew Stuchbery (The Australian National University)

IAEA-Moments-AES.pdf

10:25 Coffee break

3 Nuclear moments of short-lived isomeric states – experimental techniques, recent studies and ideas for future developments

The lifetimes of nuclear states span many orders of magnitude, requiring experimental techniques to be tailored to both their production mechanisms and their half-lives. Nuclear magnetic moment studies rely on the interaction between nuclear spins and external electromagnetic fields. Consequently, the feasibility of such measurements is determined by the state’s lifetime and the strength of the fields to which the nuclei can be exposed.

For isomeric states with half-lives between ~1 ns and a few microseconds, nuclear moment studies are typically based on the observation of spin precession in an external electromagnetic field. The Time Dependent Perturbed Angular Distribution (TDPAD) technique has been the method of choice for several decades, particularly for isomers produced in fusion–evaporation reactions. However, this production mechanism is not well suited for accessing isomeric states in neutron-rich nuclei far from stability. To overcome this limitation, projectile-fragmentation reactions have been developed over the last two decades as an alternative approach, enabling studies of isomers with half-lives from roughly 200 ns up to a few microseconds. A brief overview of these developments at various international facilities will be presented, along with examples of recent measurements and a discussion of the limitations of the method.

Isomeric states with even shorter lifetimes (< ~200 ns) remain inaccessible via projectile fragmentation. To address this gap, we have recently begun exploring the application of the Time Dependent Perturbed Angular Correlation (TDPAC) technique for such short-lived states. The prospects for advancing this approach and the challenges associated with its implementation will also be discussed.

Speaker: Georgi Georgiev (IJCLab CNRS/IN2P3, Orsay, France)

Georgiev_IAEA_Dec25.pdf

12:30 Lunch break

Presentations II

4 Measuring nuclear moments using laser spectroscopy

Laser spectroscopy is used at radioactive ion beam facilities to determine magnetic dipole and electric quadrupole moments, and additionally the change in the nuclear mean-square charge radius. The correct extraction of such quantities requires the correct value of the nuclear spin but in many cases the hyperfine structure allows the spin to be independently determined. A brief introduction to some of the key experimental methods will be given, which are typically applicable to nuclear ground and isomeric states in the millisecond range or longer. A few physics cases will be used to illustrate the need for nuclear moments and issues encountered in determining them or comparing with literature.

Speaker: Prof. Bradley Cheal (University of Liverpool, UK)

momentsBC.pdf

5 Polynomial trends in nuclear electromagnetism

A global search for polynomial trends in nuclear electromagnetism will be discussed in the context of the IAEA database of evaluated nuclear moments.

Speaker: Deyan Yordanov

Wednesday 17 December

Presentations III

6 Tables of Nuclear Electromagnetic Moments

The structure and principles underlying the existing Tables and Reports will be briefly described and problem areas and recent developments summarised. Separate attention will be given to magnetic dipole moments of long and short-lived (<1.ms) states and to electric quadrupole moments.

Speaker: Nicholas Stone

10:00 Coffee break

7 The future of the nuclear moments data base

I will discuss the options to continue the maintenance of the nuclear moments data base. This should be done at two levels: continue updating the data base, and look back in time to correct occasional misprints and add missing information.

Speaker: Dimiter Balabanski (ELI-NP/IFIN-HH)

12:30 Lunch break

Roundtable discussion

Thursday 18 December

Roundtable discussion

12:30 Lunch break

Recommendations - drafting report

Friday 19 December

Drafting report - Closing