A new radioactive decay mode, true ternary fission, the decay of heavy nuclei into three comparable fragments

The ternary cluster decay of heavy nuclei has been observed in several experiments with binary coincidences between two fragments using detector telescopes (the FOBOS-detectors) with very large solid angles and placed on the opposite sides from the source of fissioning nuclei. The binary coincidences at a relative angle of $$180^{\circ }$$ correspond to binary fission or to the decay into three cluster fragments by registration of two of them in coincidences with missing nuclei of different masses (e.g. $$^{132}\hbox {Sn}$$ , $$^{52-48}\hbox {Ca}$$ , $$^{68-72}\hbox {Ni}$$ ). This marks a new step in the physics of fission-phenomena of heavy nuclei. The new decay mode has been observed more then 10 years ago by the FOBOS group in JINR (Dubna) Russia. These experimental results for the collinear cluster tri-partition, refer to the decay into three clusters of comparable masses. The observation of several other fission modes in the same system can be predicted by the potential energy surface, which show pronounced minima and valleys, they correspond to a variety of collinear ternary fission (multi-modal) decays. In the present work we discuss the various aspects of this ternary fission mode, with different mass partitions. The question of collinearity is analyzed on the basis of recent publications.