Fragmentation and damping of collective response in extended RPA

The isoscalar monopole, isovector dipole and isoscalar quadrupole excitations in 40Ca at zero and finite temperature are investigated in the quantal framework of the extended TDHF. Resonance excitations are broaden and shift down in energy due to coupling of collective modes with the 2p-2h doorway states, and the strength distributions exhibit fine structure. It is pointed out that a suitable finite range effective force is needed for a realistic description of the self-energies of the collective modes. (author)