Giant dipole resonance studies in Ba isotopes at E/A?5 MeV

Abstract

Exclusive measurements of high-energy ? rays have been performed in Ba124 and Ba136 at the same excitation energy (?49MeV) to study the properties of the giant dipole resonance (GDR) over a wide N/Z range. The high-energy ? rays are measured in coincidence with the multiplicity of low-energy ? rays to disentangle the effect of temperature (T) and angular momentum (J). The GDR parameters are extracted employing a simulated Monte Carlo statistical model analysis. The observed ?-ray spectra of Ba124 can be explained with prolate deformation, whereas a single-component Lorentzian function which corresponds to a spherical shape could explain the ?-ray spectra of Ba136. The observed GDR width in Ba136 is narrower compared to that of Ba124. The statistical model best-fit GDR cross sections are found to be in reasonable agreement with the thermal shape fluctuation model (TSFM) calculations. Further, it is shown that the variation of GDR width with T is well reproduced by the TSFM calculations over the temperature range of 1.1-1.7 MeV. 2017 American Physical Society.