Is octupole deformation sufficient to describe the properties of 'octupolly' unstable nuclei?

The ground state potential energy of even radium isotropes is analyzed in multidimensional deformation space {βλ}. The parameters βλ of all multipoles from λ = 2 up to λ = 8 are considered as independent variables. The energy is treated by the macroscopic-microscopic method with the shell correction based on the Woods-Saxon single-particle potential. Odd multipolarities of degree higher than 3 (in particular λ = 5), omitted or treated in an average way up to now, are found to be important for the properties of the nuclei considered. (orig.)