Extremely large oblate deformation of the first excited state in $^{12}$C: a new challenge to modern nuclear theory

Fuente: arXiv
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Main Authors: Ngwetsheni, C., Orce, J. N., Navrátil, P., Garrett, P. E., Faestermann, T., Bergmaier, A., Frosini, M., Bildstein, V., Brown, B. A., Burbadge, C., Duguet, T., Hadyńska-Klȩk, K., Mahgoub, M., Mehl, C. V., Pastore, A., Radich, A., Triambak, S.
Format: Preprint
Published: 2025
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author Ngwetsheni, C.
Orce, J. N.
Navrátil, P.
Garrett, P. E.
Faestermann, T.
Bergmaier, A.
Frosini, M.
Bildstein, V.
Brown, B. A.
Burbadge, C.
Duguet, T.
Hadyńska-Klȩk, K.
Mahgoub, M.
Mehl, C. V.
Pastore, A.
Radich, A.
Triambak, S.
author_facet Ngwetsheni, C.
Orce, J. N.
Navrátil, P.
Garrett, P. E.
Faestermann, T.
Bergmaier, A.
Frosini, M.
Bildstein, V.
Brown, B. A.
Burbadge, C.
Duguet, T.
Hadyńska-Klȩk, K.
Mahgoub, M.
Mehl, C. V.
Pastore, A.
Radich, A.
Triambak, S.
contents A Coulomb-excitation study of the high-lying first excited state at 4.439 MeV in the nucleus $^{12}$C has been carried out using the $^{208}$Pb($^{12}$C,$^{12}$C$^*$)$^{208}$Pb$^*$ reaction at 56 MeV and the {\sc Q3D} magnetic spectrograph at the Maier-Leibnitz Laboratorium in Munich. High-statistics achieved with an average beam intensity of approximately 10$^{11}$ ions/s together with state-of-the-art {\it ab initio} calculations of the nuclear dipole polarizability permitted the accurate determination of the spectroscopic quadrupole moment, $Q_{_S}(2_{_1}^+) = +0.076(30)$~eb, in agreement with previous measurements. Combined with previous work, a weighted average of $Q_{_S}(2_{_1}^+) = +0.090(14)$ eb is determined, which includes the re-analysis of a similar experiment by Vermeer and collaborators, $Q_{_S}(2_{_1}^+) = +0.103(20)$~eb. Such a large oblate deformation challenges modern nuclear theory and emphasizes the need of $α$ clustering and associated triaxiality effects for full convergence of $E2$ collective properties.
format Preprint
id arxiv_https___arxiv_org_abs_2506_03236
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Extremely large oblate deformation of the first excited state in $^{12}$C: a new challenge to modern nuclear theory
Ngwetsheni, C.
Orce, J. N.
Navrátil, P.
Garrett, P. E.
Faestermann, T.
Bergmaier, A.
Frosini, M.
Bildstein, V.
Brown, B. A.
Burbadge, C.
Duguet, T.
Hadyńska-Klȩk, K.
Mahgoub, M.
Mehl, C. V.
Pastore, A.
Radich, A.
Triambak, S.
Nuclear Experiment
Nuclear Theory
Data Analysis, Statistics and Probability
A Coulomb-excitation study of the high-lying first excited state at 4.439 MeV in the nucleus $^{12}$C has been carried out using the $^{208}$Pb($^{12}$C,$^{12}$C$^*$)$^{208}$Pb$^*$ reaction at 56 MeV and the {\sc Q3D} magnetic spectrograph at the Maier-Leibnitz Laboratorium in Munich. High-statistics achieved with an average beam intensity of approximately 10$^{11}$ ions/s together with state-of-the-art {\it ab initio} calculations of the nuclear dipole polarizability permitted the accurate determination of the spectroscopic quadrupole moment, $Q_{_S}(2_{_1}^+) = +0.076(30)$~eb, in agreement with previous measurements. Combined with previous work, a weighted average of $Q_{_S}(2_{_1}^+) = +0.090(14)$ eb is determined, which includes the re-analysis of a similar experiment by Vermeer and collaborators, $Q_{_S}(2_{_1}^+) = +0.103(20)$~eb. Such a large oblate deformation challenges modern nuclear theory and emphasizes the need of $α$ clustering and associated triaxiality effects for full convergence of $E2$ collective properties.
title Extremely large oblate deformation of the first excited state in $^{12}$C: a new challenge to modern nuclear theory
topic Nuclear Experiment
Nuclear Theory
Data Analysis, Statistics and Probability
url https://arxiv.org/abs/2506.03236