The main topic of this thesis is to describe energy levels and transition probabilities of complex deformed nuclei. This is realized mainly in a collective quadrupole-octupole model. As a side topic, microscopic random phase approximation based on single-particle calculations were carried out. The nuclei under consideration are mostly rare earths and actinides.Concerning the collective model, the corresponding model by Nikolay Minkov et al. is solved numerically for the most general case when all model parameters are allowed to vary freely. Before this thesis there was always the limitation of a so-called coherent interplay, which means that the quadrupole and octupole frequencies were assumed to be equal.In detail, the eigenvalue problem is solved by diagonalizing the unrestricted Hamiltonian in the basis of the analytic solution obtained in the case of the coherent-mode assumption. Within this scheme the yrast alternating parity band is constructed by the lowest eigenvalues having the appropriate parity at given angular momentum. As a result, the unrestricted model calculations provide a better description with the root-mean-square deviation between theory and experiment being smaller than the one in the analytic solution.
