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Interacting boson model studies of collectivity in even-even and odd-even Te isotopes

E. A. Cederlöf1,2,*, W. Teng3, Nazeef1,4, T. Wan1,5, C. Qi1,†, and Y. Zhang3

  • *Contact author: ebbace@kth.se
  • †Contact author: chongq@kth.se
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Phys. Rev. C 113, 054312 – Published 20 May, 2026

DOI: https://doi.org/10.1103/vmvz-9m19

Abstract

Background: With the recent progress in lifetime measurements, there has been strong experimental and theoretical interest in studying the evolution of the collectivity in the long Te isotopic chain.

Purpose: The purpose of the present work is to investigate the structure of low-lying excited states in even-even Te nuclei as well as the νh11/2 band in the odd-mass systems within the interacting boson model framework.

Methods: A new open-source Python package is developed to evaluate the eigenvalues and eigenfunctions of a Hamiltonian which contains both the standard n̂d and Q̂·Q̂ terms as well as higher-order terms which could be essential for triaxial deformation and mixed symmetry effects.

Results: Systematic calculations of low-spin yrast and nonyrast states in even-even Te108−124 and odd-even Te109−125 nuclei have been carried out using the newly developed Python package and compared with the neighboring Cd isotopes. From the resulting eigenfunctions, the reduced transition probabilities B(E2) are calculated and compared to adopted values. Due to the vibrational-like structure of the spectra of the Te nuclei, the Hamiltonian is dominated by the vibrational term, which is reflected in the B(E2) values. This alone does not explain the low B4/2 ratios observed in some Te nuclei. However, it is demonstrated via the contour plot that the B4/2 ratios can be highly sensitive to the higher-order terms of the Hamiltonian within specific parameter domains.

Conclusions: We demonstrate that inclusion of higher-order interactions can provide a possible explanation of the anomaly observed in certain Te isotopes. The results highlight both the importance of extended IBM Hamiltonians and the utility of pyIBM as a modern computational tool for collective nuclear structure studies.

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Phys. Rev. C 113, 054312– Published 20 May, 2026
  • Received 11 September 2025
  • Revised 7 February 2026
  • Accepted 10 April 2026
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