Speaker
Description
Lanthanum ($Z = 57$) and lutetium ($Z = 71$) serve as ideal candidates to study proton-emission effects, which can be used to test nuclear models in extreme conditions. Near the N=82 shell closure, the Lu proton-emitting isotopes display a minor oblate deformation. This is in contrast with the proton-emitting La isotope, which is far from any shell closures and shows a strong prolate deformation [1,2,3,4]. Comparing these two cases can help to disentangle proton-emission effects from nuclear shape effects. The charge radii of such short-lived isotopes can only be probed using laser spectroscopy. The precision of the mean square charge radius extraction from laser spectroscopy can be improved by incorporating experimental benchmarks for mass and field shift parameters. Such benchmarks can be established through absolute charge radii measurements of stable and long-lived radioactive isotopes using muonic x-ray spectroscopy, combined with the King-Plot analysis method [5]. In muonic x-ray spectroscopy, muons are shot on the target material, where they are captured at a high principal quantum number orbital forming muonic atoms. When this captured muon cascades down to the lower shells, x rays are emitted, providing information on the atomic levels. This in turn can be used to infer nuclear properties such as the charge radius. Measurements on lutetium isotopes ($^{175, 176}$Lu) have been successfully performed, for which the analysis of these data is currently ongoing. The near-stable La isotopes require a more complex target preparation procedure, which is currently ongoing in advance of an upcoming experiment. This presentation will focus on muonic x-ray spectroscopy measurement techniques, the measurement and analysis of muonic lutetium and the challenges posed by the dynamic hyperfine structure effect.
[1] L. S. Ferreira and E. Maglione. $^{151}$Lu: Spherical or deformed? Physical Review C, 61:021304, 1 2000.
[2] F. Soramel, A. Guglielmetti, and et al. New strongly deformed proton emitter: $^{117}$La. Physical Review C,63:031304(R), 2001.
[3] L. S. Ferreira and E. Maglione. Odd-odd deformed proton emitters. Physical Review Letters, 86:1721–1724,2 2001.
[4] A. P. Robinson, C. N. Davids, G. Mukherjee, D. Seweryniak, S. Sinha, P. Wilt, and P. J. Woods. Proton decay study of $^{150}$Lu and $^{150}Lu$$^{m}$. Physical Review C, 68:054301, 11 2003.
[5] K. König, F. Sommer, J. Lantis, K. Minamisono, W. Nörtershäuser, S. Pineda, R. Powel. Isotope-shift measurements and King-fit analysis in nickel isotopes. Phys. Rev. C 103, 054305, 2021.