Speaker
Description
For several decades, stable even-mass Cd isotopes have been considered to be textbook examples of multiphonon spherical vibrators [1] based on the excitation energy pattern of their low-lying states. However, a detailed study of $^{110}$In $\beta$ decay and subsequent beyond-mean-field theoretical calculations [2-6] suggested instead the presence of multiple shape coexistence in the $^{110}\text{Cd}$ and $^{112}\text{Cd}$ isotopes. To verify this hypothesis, it is essential to determine the shapes of low-lying $0^+$ states in stable even-even Cd nuclei. The Coulomb-excitation method [7], which enables a model-independent analysis of nuclear shapes through the use of quadrupole sum rules [7], provides a powerful tool for this type of research.
The Coulomb excitation of $^{110}\text{Cd}$ using a 187-MeV $^{60}$Ni beam was performed at the National Institute for Nuclear Physics - Legnaro National Laboratories, Italy [8]. This experiment was a part of a broader program focused on systematic Coulomb-excitation studies of $^{110}\text{Cd}$ initiated with measurements using $^{14}$N and $^{32}$S beams at the Heavy Ion Laboratory, University of Warsaw [6]. The program also included a measurements with a heavier reaction partner $^{208}$Pb, which was performed at Argonne National Laboratory, USA [9].
The $^{60}$Ni + $^{110}\text{Cd}$ experiment was carried out using the AGATA $\gamma$-ray tracking spectrometer [10,11] and the particle detection array SPIDER [12]. In total 20 states of both negative and positive parities were populated up to 3.2 MeV of excitation energy, including, in particular, the $0^+_3$ state at 1731 keV. The on-going analysis focuses on the extraction of the $\gamma$-ray intensities from which a set of electromagnetic matrix elements in $^{110}\text{Cd}$ will be obtained, including quadrupole moments of excited states. This will provide insight into the nuclear shape of the $0^+_2$ and $0^+_3$ states. The quadrupole deformation parameters for the $0^+_{1,2}$ states obtained from the experiments with the $^{14}$N and $^{32}$S beams will be presented, along with preliminary results of the analysis of the AGATA data.
References
[1] R.F. Casten, Nuclear Structure from a Simple Perspective (Oxford Univ. Press 1990)
[2] P.E. Garrett et al., Phys. Rev. C 86 (2012) 044304.
[3] P.E. Garrett et al., Phys. Rev. C 101 (2020) 044302.
[4] P.E. Garrett et al., Phys. Rev. Lett. 123 (2019) 142502.
[5] P.E. Garrett et al., Acta Phys. Pol. B Proc. Suppl. 19 (2026) 1-A14
[6] K. Wrzosek-Lipska et al., Phys. Lett. B 875 (2026) 140315
[7] M. Zielinska, Low-Energy Coulomb Excitation and Nuclear Deformation, in: The Euroschool on Exotic Beams, vol.VI, S.M. Lenzi and D. Cortina-Gil (eds.) Lecture Notes in Physics 1005, pp. 43-86 (Springer, 2022)
[8] I.Z. Pietka et al., Acta Phys. Pol. B Proc. Suppl. 18 (2025) 2-A26
[9] S. Pannu et al., presented at Fall Meeting of the American Physical Society, Division of Nuclear Physics, 17-20 October, 2025
[10] S. Akkoyun et al., Nucl. Instrum. Methods A668 (2012) 26.
[11] J.J. Valiente-Dobón et al., Nucl. Instrum. Methods A1049 (2023) 168040.
[12] M. Rocchini et al., Nucl. Instrum. Methods A971 (2020) 164030.