Multiple reflection-asymmetric type band structures in $^{220}$Th and dinuclear model T.M. Shneidman, G.G. Adamian, N.V. Antonenko, and R.V.Jolos Joint Institute for Nuclear Research, 141980 Dubna, Russia W. Scheid Institut f¨ ur Theoretische Physik der Justus-Liebig-Universit¨ at, D–35392 Giessen, Germany (Dated: Today) Abstract The negative parity bands in $^{220}$Th are analyzed within the dinuclear system model which was previously used for describing the alternating-parity bands in deformed actinides. The model is based on the assumption that cluster type shapes are produced by the motion of nuclear system in the mass-asymmetry coordinate. To describe the reflection-asymmetric collective modes character- ized by nonzero values of K , the intrinsic excitations of clusters are taken into account. The angular momentum dependence of the parity splitting and the staggering behavior of the B ( E 1) /B ( E 2) ratios as functions of angular momentum are explained. PACS numbers: 21.60.Ev,21.60.Gx arXiv:1001.5351v2 [nucl-th] 30 Jan 2010 1