• Accepted Paper

Coulomb excitation of 130Te: Evidence for weak oblate deformation near N=82

N. Sensharma et al.

Phys. Rev. C - Accepted 20 October, 2026

DOI: https://doi.org/10.1103/11zr-2d5l

Abstract

Background: Even-even tellurium isotopes, located just above the Z = 50 shell closure, are expected to exhibit near-spherical vibrational character. However, previous measurements have indicated non-zero quadrupole moments and possible shape coexistence, motivating precise studies of their electromagnetic properties. In particular, [130]Te is crucial for understanding collectivity near N = 82 and for constraining nuclear matrix elements relevant for the [130]Te → [130]Xe 0νββ decay. Purpose: To determine the electromagnetic matrix elements governing the low-lying structure of 130Te, with special emphasis on the spectroscopic quadrupole moment of the 2+1 state and the evolution of quadrupole collectivity in this transitional nucleus. Methods: A multi-step Coulomb-excitation experiment was performed at INFN-LNL using a 231-MeV [82]Se beam impinging on an enriched [130]Te target. De-exciting γ rays were detected with the AGATA array in coincidence with scattered ejectiles measured by the SPIDER detector. Electromagnetic matrix elements were extracted via a least-squares analysis of γ-ray yields using the GOSIA code, incorporating available spectroscopic constraints. The results were interpreted within the framework of quadrupole sum rules and large-scale shell-model calculations. Results: A comprehensive set of E2 and M1 matrix elements connecting low-lying states in [130]Te was determined, from which level lifetimes were deduced. The diagonal matrix element of the 2+1 state was extracted with both magnitude and sign, yielding Qs(2+1) = +0.34(1) eb, consistent with a weak oblate deformation. The deduced quadrupole invariant corresponds to a small deformation parameter ⟨β2⟩ ≈ 0.12, consistent with near-spherical structure. Shell-model calculations reproduce the overall collectivity and the sign of the quadrupole moment, although discrepancies persist for transitions involving excited 2+ states. A systematic study of even-even Te isotopes shows that the evolution of excitation energies, transition strengths, and quadrupole moments is reasonably well described, with particularly good agreement for [130]Te, while larger deviations toward the lighter isotopes ([124],[122]Te) may indicate missing correlations in the present theoretical framework. Conclusions: The results provide stringent constraints on the electromagnetic structure of 130Te, confirming its weakly collective, near-spherical character. In addition, they provide an important experimental benchmark for microscopic descriptions of 130Te, a nucleus of particular relevance to searches for 0νββ decay.

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