INTERPLAY BETWEEN ONE-BODY AND COLLISIONAL DAMPING OF COLLECTIVE MOTION IN NUCLEI

Damping of giant collective vibrations in nuclei is studied within the framework of the Landau-Vlasov kinetic equation. A phenomenological m ethod of independent sources of dissipation is proposed for taking int o account the contributions of one-body dissipation, the relaxation du e to the two-body collisions and the particle emission. An expression for the intrinsic width of slow damped collective vibrations is obtain ed. In the general case, this expression cannot be represented as a su m of the widths associated with the different independent sources of t he damping. This is a peculiarity of the collisional Landau-Vlasov equ ation where the Fermi-surface distortion effect influences both the se lf-consistent mean field and the memory effect at the relaxation proce sses. The interplay between the one-body, the two-body, and the partic le emission channels which contribute to the formation of the total in trinsic width of the isoscalar 2(+) and 3(-) and isovector 1(-) giant multipole resonances in cold and hot nuclei is discussed. We have show n that the criterion for the transition temperature T-tr between the z ero-sound and first-sound regimes in hot nuclei is different from the case of infinite nuclear matter due to the contribution from the one-b ody relaxation and the particle emission. In the case of the isovector GDR the corresponding transition can be reached at temperature T-tr=4 -5 MeV.