GDR study in ²⁸Si+¹²⁴Sn reaction at low temperature

Giant Dipole Resonance (GDR) is a powerful tool for studying the average nuclear shape at high temperature (T) and angular momentum (J). In particular the variation of the GDR width (ΓD) as a function of T and J, still remains a challenge. Although the Thermal Shape Fluctuation Model (TSFM), based on inhomogeneous damping is successfully able to describe the variation of GDR width with T and J in medium mass region, some discrepancies have been observed in A ∼ 150 mass region. It has been reported that in addition to inhomogeneous damping, the contributions from intrinsic damping needs to be included to describe the observed T- and J-dependence of the GDR width in ²⁸Si +¹²⁴Sn system at 149 MeV and 185 MeV. The intrinsic damping process is expected to have a steep T dependence. Therefore, study of the GDR in the same compound nucleus ¹⁵²Gd at lower excitation energy will provide insight into the T-dependence of the GDR damping mechanism. With this motivation, the experiment was carried out using 135 MeV pulsed ²⁸Si beam from PLF at Mumbai, bombarding an enriched 2.0 mg/cm² thick ¹²⁴Sn target producing ¹⁵²Gd at E* ∼ 71 MeV and < J > ∼ 24 ħ. The experimental setup for detecting high energy γ-rays in coincidence with low energy γ-multiplicity will be discussed. Combining the extracted GDR parameters using statistical model analysis from the present data with earlier measurement, the disentanglement of temperature and angular momentum effect on GDR width will be presented