The experiment demonstrating the break-up in the Cu foil of some fraction of fragments from binary fission of ^252 Cf(sf) is discussed. One of the features of this new effect is that at least one of the break-up products shows magic nucleon composition. The possible link of the effect with fission modes is analyzed.

New feature of the ternary alpha particle accompanied fission of the ^252 Cf(sf) is discovered in the experiment where the masses of all the decay partners were measured by the velocity–energy method with the energy threshold exceeding one MeV. Two groups of the fission events were observed with a total mass of three detected fragments less than the mass of the parent nucleus by 4 and 8 units not counting the release of 3 neutrons. The yields of such events are orders of magnitude higher than the yields of ^8 Be and ^12 C in conventional ternary fission. Possible origin of unusual events is discussed.

The binary break-up of heavy fission fragments from the 235,238 U(γ, f ) reactions, while the fragments cross a solid medium, were observed for the first time. The experiments were performed at the beam of the M-T‑25 microtron at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, using VEGA (V-E Guide based Array) setup. Fission fragments were captured by the electrostatic guide system four meters long and transported in the time-of-flight spectrometer. The results let us to suppose that the fragments undergoing the break-up were born in the shape isomer states with a typical lifetime of more than 400 ns.

New results demonstrating the so-called Ni-bump being the most populated mode of the collinear cluster tripartition (CCT) of 252Cf(sf) are presented. The physical scenario of this effect is discussed. It is tested by calculations of potential energy surfaces for the fission of the intermediate fragments formed after first rupture of the mother nucleus. Fission barriers are extracted and mass asymmetries at saddles are compared with the masses of the fission fragments that take part in the Ni-bump.

In our previous publications, we discussed various manifestations of a new decay channel of the low excited heavy nuclei, dubbed collinear cluster tri-partition (CCT). The most populated CCT mode was revealed in the mass correlation distribution of fission fragments as a local region (‘‘bump’’) of increased yields below the loci linked to the conventional binary fission. The bump was named ‘‘Ni-bump’’ because it is centered at the masses associated with the magic isotopes of Ni. In the new experiment, we have modified essentially hardware and software used in our previous experiments. New experimental data were obtained for the ^235 U( γ,f ) reaction. The results complement our knowledge about the CCT mechanism, in particular its relationship with the shape isomer states in fission fragments.

The results of two methodically different experiments dedicated to the effect of a break-up of fission fragment while it passing through a solid-state foil are discussed. The hypothesis is confirmed that some part of fission fragments which were born in the shape isomer states undergo a break-up due to inelastic scattering in the foil.

Specific linear structures in the region of a big missing mass in the fission fragments mass correlation distributions were revealed due to effective cleaning of this region from the background linked with scattered fragments. One of the most pronounced structures looks like a rectangle bounded by the magic nuclei. The fission events aggregated in the rectangle show a very low total kinetic energy. We propose possible scenario of forming and decay of the multi-cluster pre-scission configuration decisive for the experimental findings.

Specific mode of the collinear cluster tri-partition of the252Cf nucleus is discussed. The structure manifests itself as a rhombic-spiral structure in the fission fragments correlation mass distribution.

In our previous publications we discussed various manifestations of a new decay channel of the low excited heavy nuclei called collinear cluster tri-partition (CCT). The most populated CCT mode was revealed in the mass correlation distribution of fission fragments (FFs) as a local region ("bump") of increased yields below the loci linked to the conventional binary fission. The bump was dubbed "Ni-bump" because it is centered at the masses associated with the magic isotopes of Ni. Intriguing features of the CCT, especially high collinearity of the CCT partners and relatively high probability comparable with that typical for conventional ternary fission, have caused rather wide discussion. In the majority of dedicated publications, the FFs partitions from the Ni-bump have been analyzed from the different points of view. In our publications, we have underlined that Ni-bump manifests itself at the detectable level only in the spectrometer arm that faces the source backing. So far, this fact has been left beyond the scope of all known theoretical considerations, while the backing likely plays a crucial role in the observation of the CCT experimental pattern.

A time-of-flight spectrometer was used to compare the masses of nuclear fission fragments before and after their passage through the carbon foil, event by event. For all the registered fragments, there was a significant loss of mass of the fragment, and the registered fragment-residue turned out to be a magic nucleus. For spontaneous fission of 252Cf nuclei, the effect was observed for both light and heavy mass peaks. This gives grounds to assume that the fragment of the conventional binary fission is born in the shape isomer state, which looks like a di-nuclear system consisting of a magical core and a light cluster.

In our previous publications we discussed possible physical scenario standing behind rectangular–like structures in the fission fragments mass-correlation distributions from 252Cf(sf). The rectangle is bounded by the known magic nuclei such as 68Ni, 84Se and others. The fission events aggregated in the rectangle show extremely low total kinetic energies. Previously only decay mode with two Ni clusters in the exit channel was discussed. A more complete analysis is presented which gives additional arguments in favour of true quaternary fission of 252Cf (sf).

The manifestation of a new original effect appearing at crossing of the metal foils by fission fragments is reported. The effect takes place predominantly at front impacts. The obtained results suggest that a fragment from conventional binary fission is borne in shape-isomer state which looks like a di-nuclear system with magic core.

In a series of the experiments at different time-of-flight spectrometers of heavy ions we have observed manifestations of a new at least ternary decay channel of low excited heavy nuclei. Due to specific features of the effect, it was called collinear cluster tri-partition (CCT). The experimental results obtained initiated a number of theoretical articles dedicated to different aspects of the CCT. In the report we compare the theoretical predictions with our experimental data, only partially published so far. The developed model of one of the most populated CCT modes that gives rise to the so called "Ni-bump" is discussed.

In a series of the experiments at different time-of-flight spectrometers of heavy ions we have observed manifestations of a new at least ternary decay channel of low excited heavy nuclei. Due to specific features of the effect, it was called collinear cluster tri-partition (CCT). The experimental results obtained initiated a number of theoretical articles dedicated to different aspects of the CCT. We compare theoretical predictions with our experimental data, only partially published so far. The model of one of the most populated CCT modes that gives rise to the so called Ni-bump is discussed. Detection of the 68-72Ni fission fragments with a kinetic energy E<25 MeV at the mass-separator Lohengrin is proposed for an independent experimental verification of the CCT.