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 $^{110,112}$In $\beta^{+}$/EC decay and $^{112}$Ag $\beta^{-}$ decay, as well as subsequent beyond-mean-field theoretical calculations [2-6] suggested instead the presence of multiple shape coexistence in the $^{110}$Cd and $^{112}$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 [8,9], provides a powerful tool for this type of research.
The Coulomb excitation of $^{110}$Cd [10] and $^{112}$Cd [11] using a 187-MeV $^{60}$Ni beam were performed at the National Institute for Nuclear Physics - Legnaro National Laboratories, Italy. These experiments were a part of a broader program focused on systematic Coulomb-excitation studies of even-even Cd isotopes initiated with measurements of $^{110}$Cd using $^{14}$N and $^{32}$S beams at the Heavy Ion Laboratory, University of Warsaw [6].
The $^{60}$Ni + $^{110,112}$Cd experiments were carried out using the AGATA $\gamma$-ray tracking spectrometer [12,13] and the particle detection array SPIDER [14]. In both cases about 20 states of both negative and positive parities were populated up to about 3 MeV of excitation energy, including, in particular, the $0^+_{1,2,3}$ states.
The analysis of $^{110}$Cd focuses on the~extraction of the $\gamma$-ray intensities from which a set of electromagnetic matrix elements 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 preliminary result on the overall deformation of $0^+_3$ state in $^{110}$Cd will be presented. Additionally, the current status of the on-going analysis of the AGATA data collected for $^{112}$Cd will be reported.
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] D. Cline, Annu. Rev. Nucl. Part. Sci. 36 (1986) 683.
[9] K. Kumar, Phys. Rev. Lett. 28 (1972) 249.
[10] I.Z. Pietka et al., Acta Phys. Pol. B Proc. Suppl. 18 (2025) 2-A26
[11] K. Jakowinicz, BSc. thesis in preparation. University of Warsaw, Poland
[12] S. Akkoyun et al., Nucl. Instrum. Methods A668 (2012) 26.
[13] J.J. Valiente-Dob\'on et al., Nucl. Instrum. Methods A1049 (2023) 168040.
[14] M. Rocchini et al., Nucl. Instrum. Methods A971 (2020) 164030.