g-factor measurements on νg9/2 isomeric states in 67,69,70Ni
Abstract
Background: The region around N=40 in the Ni isotopes has attracted considerable interest both from an experimental and theoretical point of view over the last few decades after Ni68 was proposed as a doubly magic nucleus. However, the experimental evidence has proven contradictory and inconclusive. Measurements of magnetic dipole moments in the adjacent Ni67,69,70 would be sensitive to the purity of the nuclear wave function in the vicinity of Ni68. Purpose: Investigate the single-particle structure of several νg9/2 isomeric states in neutron-rich Ni isotopes, namely the 9/2+ isomer in Ni67 (Ex=1007 keV, T1/2=13.3(2)µs, expected νg9/2 configuration), the (17/2−) isomer in Ni69 (Ex=2700 keV, T1/2=439(3)ns, expected νp1/2−1g9/22 configuration), and the 8+ isomer in Ni70 (Ex=2861 keV, T1/2=232(1)ns, expected νg9/22 configuration), via g-factor measurements. Methods: The isomers were populated and spin-aligned in an intermediate-energy projectile-fragmentation reaction of a Ge76 beam in an experiment at NSCL, MSU. The g factors of the Ni isomeric states were determined using the time-dependent perturbed angular distribution technique. Results: The half-lives of the isomers in Ni67,70, as well as that of the (6−) isomer in Cu72, were confirmed, the precision on the half-life of the (19/2−) isomer in Cu71 was improved, and a new value was obtained for the half-life of the isomer in Ni69. The g factors of the isomers in Ni69,70 were determined for the first time, while the remeasured g factor of the 9/2+ isomer in Ni67 resolves an existing discrepancy between experiment and theory. Conclusions: The obtained results and the systematics of the νg9/2 g factors in the region were compared to state-of-the-art shell-model calculations using the JUN45 and the LNPS interactions. Excluding proton excitations from the Ni56 core, as in the JUN45 interaction, requires a significant reduction of the single-nucleon spin g factors to reproduce the data (gseff≤0.75gsfree). Including proton excitations across the Z=28 shell closure, as in the LNPS interaction, reproduces the g factors of the Ni and Zn isotopes in the region by using a small reduction of 0.9 gsfree.
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BibTeX
@article{stoychev2026gfactor,
title = {{g-factor measurements on νg9/2 isomeric states in 67,69,70Ni}},
author = {K. Stoychev and G. Georgiev and J Ljungvall and K Sieja and A.M Amthor and D.L Balabanski and G Belier and M Danchev and J.M Daugas and T.N Ginter and G Goldring and M Hausmann and I. Matea and W Mueller and B.S Nara Singh and G Neyens and O Perru and O Roig and A Saltarelli and A Stolz and N Vermeulen and D.T Yordanov},
journal = {Physical Review C},
year = {2026},
month = sep,
doi = {10.1103/2f9y-d3dy},
url = {https://hal.science/hal-05693234v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - g-factor measurements on νg9/2 isomeric states in 67,69,70Ni
AU - K. Stoychev
AU - G. Georgiev
AU - J Ljungvall
AU - K Sieja
AU - A.M Amthor
AU - D.L Balabanski
AU - G Belier
AU - M Danchev
AU - J.M Daugas
AU - T.N Ginter
AU - G Goldring
AU - M Hausmann
AU - I. Matea
AU - W Mueller
AU - B.S Nara Singh
AU - G Neyens
AU - O Perru
AU - O Roig
AU - A Saltarelli
AU - A Stolz
AU - N Vermeulen
AU - D.T Yordanov
PY - 2026
DA - 2026/09/25
JO - Physical Review C
DO - 10.1103/2f9y-d3dy
UR - https://hal.science/hal-05693234v1
AB - Background: The region around N=40 in the Ni isotopes has attracted considerable interest both from an experimental and theoretical point of view over the last few decades after Ni68 was proposed as a doubly magic nucleus. However, the experimental evidence has proven contradictory and inconclusive. Measurements of magnetic dipole moments in the adjacent Ni67,69,70 would be sensitive to the purity of the nuclear wave function in the vicinity of Ni68. Purpose: Investigate the single-particle structure of several νg9/2 isomeric states in neutron-rich Ni isotopes, namely the 9/2+ isomer in Ni67 (Ex=1007 keV, T1/2=13.3(2)µs, expected νg9/2 configuration), the (17/2−) isomer in Ni69 (Ex=2700 keV, T1/2=439(3)ns, expected νp1/2−1g9/22 configuration), and the 8+ isomer in Ni70 (Ex=2861 keV, T1/2=232(1)ns, expected νg9/22 configuration), via g-factor measurements. Methods: The isomers were populated and spin-aligned in an intermediate-energy projectile-fragmentation reaction of a Ge76 beam in an experiment at NSCL, MSU. The g factors of the Ni isomeric states were determined using the time-dependent perturbed angular distribution technique. Results: The half-lives of the isomers in Ni67,70, as well as that of the (6−) isomer in Cu72, were confirmed, the precision on the half-life of the (19/2−) isomer in Cu71 was improved, and a new value was obtained for the half-life of the isomer in Ni69. The g factors of the isomers in Ni69,70 were determined for the first time, while the remeasured g factor of the 9/2+ isomer in Ni67 resolves an existing discrepancy between experiment and theory. Conclusions: The obtained results and the systematics of the νg9/2 g factors in the region were compared to state-of-the-art shell-model calculations using the JUN45 and the LNPS interactions. Excluding proton excitations from the Ni56 core, as in the JUN45 interaction, requires a significant reduction of the single-nucleon spin g factors to reproduce the data (gseff≤0.75gsfree). Including proton excitations across the Z=28 shell closure, as in the LNPS interaction, reproduces the g factors of the Ni and Zn isotopes in the region by using a small reduction of 0.9 gsfree.
SN - 2469-9985
SN - 2469-9993
ER -