Spontaneous fission, cluster emission and alpha decay of 222Ra in a unified description

Three disintegration modes of the parent nucleus 222Ra, namely the fission, the cluster emission and the alpha decay, are treated in a unified manner. The half-lives are calculated by taking into account the penetration probabilities through the potential barrier along disintegration trajectories in the deformation space appropriate to each kind of decay. These trajectories start from the same parent ground state configuration. The disintegration paths are obtained from the least action principle. The deformation energy is calculated within the macroscopic-microscopic procedure based on the Woods-Saxon two center shell model. The effective mass is determined microscopically with the cranking method and the Gaussian Overlap Approximation. The nuclear shape parametrization is characterized by the most important five degrees of freedom encountered in fission, corresponding to the elongation, the mass asymmetry, the necking and the two fragment deformations. Partial half-life results for alpha-decay and cluster emission processes treated as superasymmetric fission agree with the experimental data. The spontaneous fission half-life is predicted. Molecular states are evidenced for the superasymmetric fission process as a result of the large shell effects in the nascent fragments.