High-Resolution Laser Spectroscopy on the Hyperfine Structure of $^{255}$Fm (Z=100)
Abstract
We report on high-resolution laser spectroscopy of Fm (h), one of the heaviest nuclides available from reactor breeding. The hyperfine structures in two different atomic ground-state transitions at 398.4~nm and 398.2~nm were probed by in-source laser spectroscopy at the RISIKO mass separator in Mainz, using the PI-LIST high-resolution ion source. Experimental results were combined with hyperfine fields from various atomic ab-initio calculations, in particular using MultiConfigurational Dirac-Hartree-Fock theory, as implemented in GRASP18. In this manner, the nuclear magnetic dipole and electric quadrupole moments were derived to be and ~eb, respectively. The magnetic moment indicates occupation of the ~7/2[613] Nilsson orbital, while the large quadrupole moment confirms strong, stable prolate deformation consistent with systematics in the heavy actinides. Comparisons with available expectation values from nuclear theory show good agreement, providing a stringent benchmark for the used theoretical models. These results revise earlier data and establish Fm as a reference isotope for future high-resolution studies.
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Cite
@article{arxiv.2511.20921,
title = {High-Resolution Laser Spectroscopy on the Hyperfine Structure of $^{255}$Fm (Z=100)},
author = {M. Urquiza-González and M. Stemmler and T. E. Albrecht and B. Bally and M. Bender and S. Berndt and M. Block and A. Brizard and J. S. Andrews and J. Bieron and P. Chhetri and H. Dorrer and C. E. Düllmann and J. G. Ezold and S. Goriely and M. J. Gutiérrez and D. Hanstorp and R. Hasse and R. Heinke and K. Hens and S. Hilaire and M. Kaja and T. Kieck and N. Kneip and U. Köster and A. T. Loria Basto and C. Mokry and D. Münzberg and K. Myhre and T. Niemeyer and S. Péru and S. Raeder and D. Renisch and J. Runke and S. K. Schrell and D. Studer and K. van Beek and J. Warbinek and K. Wendt},
journal= {arXiv preprint arXiv:2511.20921},
year = {2025}
}