The multiphonon method is applied to heavy nuclei using the collective $K=0^{-}$ octupole state as the building phonon. A good description of the $K=0^{-}$ band is possible even at low energy $E$ where the random-phase approximation fails. It also becomes clear why one has not observed $K=0^{+}$ states with an energy of the order of $2E$.

NUCLEAR STRUCTURE Multiphonon states of octupole nature in even-even deformed nuclei with mass number $222\le A\le 228$.

• Received 27 September 1982

DOI:https://doi.org/10.1103/PhysRevC.27.2968