Interfering states and narrow resonances at high excitation energy

A schematic model of multipole giant resonances is considered which treats the external interaction of the resonance states via common decay channels on the same footing as the internal residual interaction. At high excitatio n energy, the cross-section pattern is governed by the phenomenon of resona nce trapping, i.e. by the formation of different time scales. The interplay of internal and external collectivity influences significantly the distrib ution of the dipole strengths over the single states as well as their width s and positions in energy. A realistic calculation is performed for Pb-208. The strength function of the 4 (h) over bar w isoscalar monopole giant res onance is obtained in the framework of the random phase approximation in th e continuum. The one-particle continuum is shown to play an important role in the formation of the structure of the strength function. Some narrow res onances appear due to resonance trapping.