Odd-Even Staggering in Gamma Vibrational Bands of Deformed Nuclei Insights from Collective Models and Machine Learning Approaches
DOI:
https://doi.org/10.56042/ijpap.v64i9.22036Keywords:
Light GBM, Machine learning, Odd-even staggering, Gamma band, Asymmetry parameter, Gd isotopes, Collective modelsAbstract
The odd-even spin staggering of gamma-vibrational bands is examined for even-even Gd isotopes in the rare-earth region. The work uses experimental gamma-band energies, the empirical staggering index S(J), the energy ratio R4/2, and the asymmetry parameter gamma0 to follow the evolution from gamma-soft behaviour toward more axially deformed rotational structures. The analysis is framed by collective-model ideas, especially the interacting boson model and the triaxial rotor picture, because both connect gamma-band level splitting with the softness or rigidity of the nuclear shape. A LightGBM regression procedure is further used only as a data-support tool for the missing S(7) and S(8) entries at N = 94. The imputed values are inserted with uncertainty estimates so that the observed trend of the Gd chain can be discussed without leaving artificial gaps in the systematics. The results show strong staggering near the transitional neutron numbers and a close relation between S(J), R4/2 and asymmetry parameter. These observations support the view that gamma-band staggering is a sensitive indicator of triaxial effects, shape evolution and symmetry changes in deformed nuclei.
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