Temperature and spin dependence of the giant dipole resonance width

The dependence of the GDR width on temperature and spin was investigated in Sn nuclei, by using the reactions 17O + 100Mo and 18O + 100Mo to form 117Sn and 118Sn, respectively. Widths of Γ=6.9±0.5MeV and Γ=8.2±0.5MeV were extracted for temperatures of 1.74 and 1.84 MeV, respectively. The large increase of the width over this relatively small temperature range is inconsistent with the thermal shape fluctuation model. However, the spin dependence of the width is well reproduced by the model.