Interplay between one-body and collisional damping of collective motion in nuclei.

Abstract

Damping of giant collective vibrations in nuclei is studied within the framework of the Landau-Vlasov kinetic equation. A phenomenological method of independent sources of dissipation is proposed for taking into account the contributions of one-body dissipation, the relaxation due to the two-body collisions and the particle emission. An expression for the intrinsic width of slow damped collective vibrations is obtained. In the general case, this expression cannot be represented as a sum of the widths associated with the different independent sources of the damping. This is a peculiarity of the collisional Landau-Vlasov equation where the Fermi-surface distortion effect influences both the self-consistent mean field and the memory effect at the relaxation processes. The interplay between the one-body, the two-body, and the particle emission channels which contribute to the formation of the total intrinsic width of the isoscalar ${2}^{+}$ and ${3}^{\mathrm{\ensuremath{-}}}$ and isovector ${1}^{\mathrm{\ensuremath{-}}}$ giant multipole resonances in cold and hot nuclei is discussed. We have shown that the criterion for the transition temperature ${\mathit{T}}_{\mathrm{tr}}$ between the zero-sound and first-sound regimes in hot nuclei is different from the case of infinite nuclear matter due to the contribution from the one-body relaxation and the particle emission. In the case of the isovector GDR the corresponding transition can be reached at temperature ${\mathit{T}}_{\mathrm{tr}}$=4--5 MeV. \textcopyright{} 1996 The American Physical Society.