A study of the almost sequential mechanism of true ternary fission

We consider the collinear ternary fission which is a sequential ternary decay with a very short time between the ruptures of two necks connecting the middle cluster of the ternary nuclear system and outer fragments. In particular, we consider the case where the Coulomb field of the first massive fragment separated during the first step of the fission produces a lower pre-scission barrier in the second step of the residual part of the ternary system. In this case, we obtain a probability of about $10^{-3}$ for the yield of massive clusters such as \nuclide[70]{Ni}, \nuclide[80-82]{Ge}, \nuclide[86]{Se}, and \nuclide[94]{Kr} in the ternary fission of \nuclide[252]{Cf}. These products appear together with the clusters having mass numbers of $A = 132$--$140$. The results show that the yield of a heavy cluster such as \nuclide[68-70]{Ni} would be followed by a product of $A = 138$--$148$ with a large probability as observed in the experimental data obtained with the FOBOS spectrometer at the Joint Institute for Nuclear Research. The third product is not observed. The landscape of the potential energy surface shows that the configuration of the Ni + Ca + Sn decay channel is lower about 12 MeV than that of the Ca + Ni + Sn channel. This leads to the fact, that the yield of Ni and Sn is large. The analysis on the dependence of the velocity of the middle fragment on mass numbers of the outer products leads to the conclusion that, in the collinear tripartition channel of \nuclide[252]{Cf}, the middle cluster has a very small velocity, which does not allow it to be found in experiments.Comment: 11 pages, 9 figure

2-n-Butyl-6-chloro-1-(2,4-dimethyl­phenyl­sulfon­yl)-1H-benzimidazole–2-n-butyl-5-chloro-1-(2,4-dimethyl­phenyl­sulfon­yl)-1H-benzimidazole (0.759/0.241)

The title compound, 0.759C19H21ClN2O2S·0.241C19H21ClN2O2S, was synthesized by aryl­sulfonyl­ation of 2-n-butyl-5-chloro-1H-benzimidazole in the presence of triethyl­amine. The crystal structure is composed of two mol­ecules, 2-n-butyl-6-chloro-1-(2,4-dimethylphenyl­sulfon­yl)-1H-benzimidazole and 1-(2,4-dimethylphenyl­sulfon­yl)-2-n-butyl-5-chloro-1H-benz­imidazole, in the refined ratio of 0.759 (4):0.241 (4) disordered at the same position in the unit cell. The mol­ecule has three essentially planar fragments viz. benzimidazole, dimethyl­benzene and n-butyl (r.m.s. deviations of 0.009, 0.024 and 0.003 Å, respectively). The angle between the benzimidazole and dimethyl­benzene fragments is 86.0 (1)°. In the crystal, pairs of inter­molecular C—H⋯π inter­actions form centrosymmetrical dimers, which are linked by weak inter­molecular C—H⋯O hydrogen bonds

Collinear cluster tripartition as sequential binary fission in the 235^{235}U(nth_{\rm th},f) reaction

The mechanism leading to the formation of the observed products of the collinear cluster tripartition is carried out within the framework of the model based on the dinuclear system concept. The yield of fission products is calculated using the statistical model based on the driving potentials for the fissionable system. The minima of potential energy of the decaying system correspond to the charge numbers of the products which are produced with large probabilities in the sequential fission (partial case of the collinear cluster tripartition) of the compound nucleus. The realization of this mechanism supposes the asymmetric fission channel as the first stage of sequential mechanism. It is shown that only the use of the driving potential calculated by the binding energies with the shell correction allows us to explain the yield of the true ternary fission products. The theoretical model is applied to research collinear cluster tripartition in the reaction $^{235}$U(n$_{\rm th}$,f). Calculations showed that in the first stage of this fission reaction, the isotopes $^{82}$Ge and $^{154}$Nd are formed with relatively large probabilities and in the second stage of sequential fission of the isotope Nd mainly Ni and Ge are formed. This is in agreement with the yield of the isotope $^{68}$Ni which is observed as the product of the collinear cluster tripartition in the experiment.Comment: 20 pages, 9 figure

Pre-scission configuration of the tri-nuclear system at spontaneous ternary fission of

The potential energy surface for the pre-scission configurations of tri-nuclear systems formed in the spontaneous ternary fission of 252Cf is calculated. The fission channel 70Ni + 50Ca + 132Sn is chosen as one of the more probable channels of true ternary fission of 252Cf . A study of the collinear arrangement of the reaction products for true ternary fission is the aim of this work. The results are presented as a function of the relative distance R12 between the centres of mass of 70Ni and 132Sn and the distance from the centre of mass of 50Ca , which is perpendicular to R12. The results show that only for a particular range of the R12 values the collinear tripartion of the fissioning nucleus occurs

N-(5-Benzylsulfanyl-1,3,4-thiadiazol-2-yl)-2-(piperidin-1-yl)acetamide

The title compound, C16H20N4OS2, was synthesized by the reaction of 2-benzylsulfanyl-5-chloroacetamido-1,3,4-thiadiazole and piperidine in a 1:2 ratio. The planes of the acetamide and 1,3,4-thiadiazole units are twisted by 10.8 (4)°. The thiadiazole S atom and the acetamide O atom are syn-oriented due to a hypervalent S...O interaction of 2.628 (4) Å. In the crystal, molecules form centrosymmetric dimers via N—H...N hydrogen bonds. These dimers are further connected by C—H...O interactions into (100) layers