Octupole deformation in even-even Rn-Th nuclei

The ground-state properties and high-spin spectra of the light even-even Rn-Th nuclei have been systematically investigated using the cranking shell model in a multidimentional deformation space, including beta(2), beta(3), beta(4) and beta(5) degrees of freedom. Calculations reproduce well the experimental values of the moment of inertia. The investigation of the structures shows that, with increasing neutron number, the ground-state shapes of these nuclei evolve from nearly spherical(N approximate to 130), through well-developed octupole (N approximate to 136) to well-deformed quadrupole (N >= 140) shapes. Cranking calculations display that the nuclei investigated axe very octupole soft and will restore to reflection-symmetric shapes at high spin.