MICROSCOPIC DESCRIPTION OF 2-PHONON STATES IN SLIGHTLY ANHARMONIC NUCLEI

A self-consistent approach is developed for describing two-phonon states in nonmagic nuclei with slightly anharmonic properties. This approach is based on the method of an energy-density functional, the quasiparticle random-phase approximation, and a Green's-function method which makes it possible to evaluate phonon interaction diagrams in the coordinate representation. The transition density of the two-phonon state [3(1)- x 3(1)-]6+ in Zr-96 is calculated by this approach. An admixture of two-phonon configurations in low-lying collective states may shift the surface peak in the corresponding transition charge density into the interior of the nucleus. The 6(1)+ Sr-86 state is used as an example to demonstrate this effect.