Angular momentum dependence of the giant dipole resonance width in excited nuclei of mass

Gamma ray spectra in the energy range of 4–25 MeV were measured in the reaction ²⁸Si + ¹²⁴Sn at E(²⁸Si) 150 MeV in coincidence with low energy γ-multiplicities. The spectra were analysed using a simulated Monte Carlo CASCADE code. The centroid energy and width of the giant dipole resonance were extracted for various multiplicity windows. The average angular momentum and temperature of the final states populated after the giant dipole photon emission range from 25 and 1.5 MeV to 56 and 1.3 MeV, respectively. The extracted widths are almost constant for the lower multiplicity windows and show an increase of 1.4 MeV at the highest window. The nuclei are expected to be near the liquid drop regime and the experimental results are not inconsistent with the liquid drop behaviour.