Entrance channel effects in the population of giant dipole resonances in Sn nuclei

We have measured the high energy gamma-ray spectra from the fusion reaction s 130 MeV O-16 + Mo-98 and 240 MeV Ti-48 + Ni-64, populating the Sn-114 and Sn-112 compound nuclei at the excitation energy of 108 MeV. The comparison of the spectra shows a similar to 38% enhancement of the gamma-ray yield i n the Giant Dipole Resonance region (E(gamma)greater than or equal to 18 Me V) when the O-16 induced reaction is considered. The experimental result is consistent with entrance channel effects related to the N/Z asymmetry betw een the target and the projectile.