Microscopic description of damped collective motion

The damping mechanism of the damped collective motion is studied microscopically on the basis of the linear response theory. As for isovector modes the giant dipole resonance built on highly excited states in 208Pb is considered. The width due to the two-body collisional damping is found to be able to reproduce well the temperature dependence of the observed width. As for isoscalar modes, the slow collective motion like fission is studied. The transport coefficients, friction γ, inertia M and local stiffness C are computed along a fission path of 224Th. The calculated effective damping rate η=γ/(2√(M|C|)) at the saddle is in qualitative agreement with the observed one which increases markedly with temperature. More realistic description of solving the transport equation is necessary to get the quantitative agreement. The approximate functional form of the friction is provided for that. Moreover, it is noticed that the effect of shell structure on the friction should be taken into account as well as the shell correction energy in the theoretical estimate of the production of super heavy elements based on the transport equation