DAMPING OF NUCLEAR COLLECTIVE MOTIONS WITHIN THE METHOD OF PHASE-SPACE MOMENTS OF THE WIGNER DISTRIBUTION FUNCTION

The semiclassical method of the equations of motion for the phase-spac e moments of the Wigner function is extended to the inclusion of dampi ng mechanisms. The gross structure of the strength function is obtaine d going beyond the scaling approximation. Two-body correlations are in troduced through an extended relaxation-time approximation. A realisti c Skyrme-type interaction is used to derive the self-consistent potent ial. An application is shown to the damping of the giant monopole reso nance (GMR) in Pb-208. The calculated spreading widths with a relaxati on-time parameter determined microscopically for the ''collisional'' d amping are very much below the observed values. On the other side, con sistency is found between the description of the widths of monopole, q uadrupole and octupole giant resonances with an empirical value of the relaxation-time parameter.