The Width of the Giant-dipole Resonance Built On Excited-states of Cu Compound Nuclei

Continuum gamma-ray spectra from the decay of Cu-59 formed at an excitation energy of 100 MeV and angular momenta up to 43h by means of the reaction 190 MeV S-32 +Al-27 have been measured and analyzed. The parameters of the Giant Dipole Resonance (GDR) have been extracted using the statistical model. The derived GDR width confirms the sizeable broadening of this resonance in Cu-59 already reported in our earlier investigation at 77 MeV excitation energy (J(crit) = 38h). Estimates of the GDR width have been performed in the adiabatic approximation. Predicted values account qualitatively for the experimental data of Cu-59 as well as of the heavier isotope Cu-63, in which the broadening was not seen up to 77 MeV excitation (J(crit) = 35h). The present analysis demonstrates the strong sensitivity of the GDR to spin effects in this mass region.