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.

Careful studies of the fission fragments mass correlation distributions let us to reveal specific linear structures in the region of a big missing mass. It became possible due to applying of effective cleaning of this region from the background linked with scattered fragments. One of the most pronounced structure 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 prescission configuration decisive for the experimental findings. This approach is valid as well for treating of another rare decay modes discovered in the past.

Background: In a series of 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 obtained experimental results have initiated a number of theoretical articles dedicated to different aspects of the CCT. Special attention was paid to kinematics constraints and stability of collinearity. Purpose: To compare theoretical predictions with our experimental data, only partially published so far. To develop the model of one of the most populated CCT modes that gives rise to the so-called "Ni-bump." Method: The fission events under analysis form regular two-dimensional linear structures in the mass correlation distributions of the fission fragments. The structures were revealed both at a highly statistically reliable level but on the background substrate, and at the low statistics in almost noiseless distribution. The structures are bounded by the known magic fragments and were reproduced at different spectrometers. All this provides high reliability of our experimental findings. The model of the CCT proposed here is based on theoretical results, published recently, and the detailed analysis of all available experimental data. Results: Under our model, the CCT mode giving rise to the Ni bump occurs as a two-stage breakup of the initial three body chain like the nuclear configuration with an elongated central cluster. After the first scission at the touching point with one of the side clusters, the predominantly heavier one, the deformation energy of the central cluster allows the emission of up to four neutrons flying apart isotropically. The heavy side cluster and a dinuclear system, consisting of the light side cluster and the central one, relaxed to a less elongated shape, are accelerated in the mutual Coulomb field. The "tip" of the dinuclear system at the moment of its rupture faces the heavy fragment or the opposite direction due to a single turn of the system around its center of gravity. Conclusions: Additional experimental information regarding the energies of the CCT partners and the proposed model of the process respond to criticisms concerning the kinematic constraints and the stability of collinearity in the CCT. The octupole deformed system formed after the first scission is oriented along the fission axis, and its rupture occurs predominantly after the full acceleration. Noncollinear true ternary fission and far asymmetric binary fission, observed earlier, appear to be the special cases of the decay of the prescission configuration leading to the CCT. Detection of the Ni68-72 fission fragments with a kinetic energy E < 25MeV at the mass-separator Lohengrin is proposed for an independent experimental verification of the CCT.

We discuss the manifestations of a new original effect appeared at crossing of the metal foils by fission fragments. We have observed significant mass deficit in the total mass M of the fission fragments detected in coincidence with ions knocked out from the foil. It was shown that at the large angles of scattering of the knocked-out ions from the foil predominantly conventional elastic Rutherford scattering takes place. As the result M corresponds to the mean mass of the mother system after emission of fission neutrons (no missing mass). In contrast, in near frontal impacts fission fragment misses essential part of it mass. Residual nuclei at least for the fragments from the heavy mass peak show magic nucleon composition.

Exotic Nuclei, pp. 284-287 (2017) No AccessNEW RESULTS IN STUDY OF SHAPE ISOMER STATES IN FISSION FRAGMENTSYu. V. Pyatkov, D. V. Kamanin, A. A. Alexandrov, I. A. Alexandrova, Z. I. Goryainova, E. A. Kuznetsova, A. O. Strekalovsky, O. V. Strekalovsky, V. E. Zhuchko, N. Mkaza and V. MalazaYu. V. PyatkovNational Nuclear Research University MEPhI (Moscow Engineering Physics Institute), 115 409 Moscow, RussiaJoint Institute for Nuclear Research, 141980 Dubna, Russia, D. V. KamaninJoint Institute for Nuclear Research, 141980 Dubna, Russia, A. A. AlexandrovJoint Institute for Nuclear Research, 141980 Dubna, Russia, I. A. AlexandrovaJoint Institute for Nuclear Research, 141980 Dubna, Russia, Z. I. GoryainovaJoint Institute for Nuclear Research, 141980 Dubna, Russia, E. A. KuznetsovaJoint Institute for Nuclear Research, 141980 Dubna, Russia, A. O. StrekalovskyJoint Institute for Nuclear Research, 141980 Dubna, Russia, O. V. StrekalovskyJoint Institute for Nuclear Research, 141980 Dubna, Russia, V. E. ZhuchkoJoint Institute for Nuclear Research, 141980 Dubna, Russia, N. MkazaUniversity of Stellenbosch, Faculty of Military Science, Military Academy, Saldanha 7395, South Africa and V. MalazaUniversity of Stellenbosch, Faculty of Military Science, Military Academy, Saldanha 7395, South Africahttps://doi.org/10.1142/9789813226548_0043Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: A brake-up of the fission fragments crossing metal foil was observed. In the light of the results obtained a fission fragment from conventional binary fission is supposed to be born in the shape isomer state which looks like di-nuclear system consisting of the magic core and lighter cluster. Keywords: Ternary fissionShape-isomer states FiguresReferencesRelatedDetails Exotic NucleiMetrics History KeywordsTernary fissionShape-isomer statesPDF download

A new off-line timing method for PIN diode signals is presented which allows the plasma delay effect to be suppressed. Velocities of heavy ions measured by the new method are in good agreement within a wide range of masses and energies with velocities measured by time stamp detectors based on microchannel plates.

We discuss the quality of heavy ions (HI) mass reconstruction in the wide range of HI energies and masses using Si PIN diodes for measuring both energy and time-of-flight. The results are based on the experimental data obtained at the IC-100 accelerator in the Flerov Laboratory of the JINR (Dubna, Russia).