Nuclear dissipation and the giant dipole resonance

The influence of nuclear dissipation on the formation and decay of compound nuclei is studied with the γ-ray decay of the giant dipole resonance (GDR) built on highly excited states. The compound nuclei 164Yb, 160Er, and 10Sn were produced with very mass-asymmetric and with more mass-symmetric target/projectile combinations. While the γ-ray spectra from the more symmetrically formed 160Er and 164Yb show large deviation from statistical model prediction, the reaction leading to 110Sn shown no such deviations. We discuss a possible explanation of these observed entrance channel effects qualitatively within the particle exchange model. 26 refs., 7 figs