Effects of ground-state correlations on damping of giant dipole resonaces in $LS$ closed shell nuclei

Abstract

The effects of ground-state correlations on the damping of isovector giant dipole resonances in LS closed shell nuclei 16 O and 40 Ca are studied using an extended random phase approximation (ERPA) derived from the time-dependent density-matrix theory. It is pointed out that unconventional twobody amplitudes of one particle-three hole and three particle-one hole types which are neglected in most extended RPA theories play an important role in the fragmentation of isovector dipole strength.