Role of magicity in the low temperature evolution of IVGDR width in Te isotopes

The low-temperature evolution of the isovector giant dipole resonance (IVGDR) width has been systematically investigated for the 116 Te, 120 Te, and 128 Te nuclei to explore the roles of shell closure, neutron-to-proton ratio, and thermal shape fluctuations in the damping of collective motion. High-energy γ -rays, produced in alpha-induced fusion reactions, were measured using the LAMBDA spectrometer, with angular-momentum selection provided by γ -multiplicity detectors. The experimental γ -ray spectra were analyzed using a statistical-model framework and Bayesian inference method was applied to extract the IVGDR parameters over the temperature range T ≈ 0.8-1.5 MeV. Subsequently, a self-consistent nuclear energy-density-functional framework was employed to calculate the IVGDR widths at finite temperature and to interpret the observed temperature dependence. For the near-spherical 128 Te nucleus, which lies close to the neutron magic number N = 82 , a stronger shell-induced inhibition of the evolution of IVGDR width is observed at low temperature compared to 116 Te and 120 Te. It has been observed that the low-temperature damping mechanism depends strongly on the proximity to shell closure, which can be quantified using a single dimensionless parameter δ m (see main text for its definition). A systematic comparison across isotopic chains in different mass regions further confirms that larger values of δ m correspond to relatively broader IVGDR widths, whereas variations in isospin asymmetry do not significantly influence the width.