Simple parametrization for octupole states in spherical and weakly deformed heavy nuclei

A simple parametrization of the frequencies of low-energy octupole phonons in spherical and weakly deformed heavy nuclei is given. It is shown that this parametrization substantially simplifies the interpretation of octupole states in the A = 70, A = 100, and A = 120 regions and provides information on the ordering and spacing of single particle orbitals in valence shells in the latter region. Finally, this parametrization is used for an investigation of the nature of the low-lying negative parity states in Ra and Th isotopes