Symmetric Fragments Research Articles

Fusion enhancement within a collective clusterization approach applied to the isotopic chain of neutron-rich light-mass compound nuclei

The dynamics of neutron-rich light-mass compound nuclei $^{24,25,26,27}\mathrm{Mg}^{*}$ formed in $^{12,13,14,15}\mathrm{C}+^{12}\mathrm{C}$ fusion reactions, respectively, is explored at different ${E}_{\mathrm{c}.\mathrm{m}.}$ values within the dynamical cluster decay model (DCM). DCM is based on the quantum mechanical fragmentation theory, which treats the binary fragmentation of emitting compound nucleus as light particles (LPs), intermediate mass fragments (IMFs), as well as symmetric mass fragments (SMFs), on equal footing, which is not the case with other fission and statistical models. All calculations are made for spherical considerations and angular momenta taken up to the $\ensuremath{\ell}$-critical value for the respective reactions. A fusion enhancement is observed as we go from compound nuclei (CN) having an even number of neutrons ($^{24,26}\mathrm{Mg}^{*}$) to CN with the odd number of neutrons ($^{25,27}\mathrm{Mg}^{*}$). Interestingly, we find that the only parameter of the DCM, the neck-length parameter $\mathrm{\ensuremath{\Delta}}R$ related to the barrier lowering, is in linear relation with ${\ensuremath{\sigma}}_{\mathrm{Fusion}}$ at chosen incident laboratory energy. The fusion enhancement is found to be larger for odd neutron number nuclei, which indicates the influence of unpaired neutrons on fusion cross sections. Within the formalism of DCM, the phenomenon of fusion enhancement finds its base in the process of collective clusterization, which is quite evident from the larger values of summed-up preformation probability for the reactions having odd mass projectiles or forming odd mass CN. The DCM calculated fusion cross sections are in good agreement with the available experimental data for the given reactions.

Four-dimensional Langevin approach to fission with Cassini shape parameterization

We apply the Cassini shape parameterization to the dynamical study of actinide fission using the multi-dimensional Langevin equation. The fragment mass distributions for fission of 236U and 256, 258 Fm are calculated with the 4D Langevin equation. The 4D collective space is formed by adding either α3 or α6 to the basic 3D {α, α1, α4} space. We investigate the role of α3 and α6 by comparing the results of 4D (α3 or α6) with that of 3D. For 236U and 256Fm, where asymmetric fission is predominant, the fragment mass distributions calculated in the 4D (α3) space are in good agreement with experimental data. On the other hand, for 258Fm, which is characterized by symmetric fission, 4D (α6) is effective for describing the shape of compact symmetric fragments. We demonstrate the advantages of the Cassini shape parameterization for the dynamical study of actinide fission.

(Invited) Sumanenyl Cations As Redox-Active Buckybowls

Sumanene is one of the pristine buckybowls, which possesses C3v symmetric fragment of C60. The most characteristic feature of its structure is that sumanene has three benzylic positions on its periphery, therefore, potentially 6 electron redox systems are considered from the corresponding trianions to trications. In this presentation, I demonstrate the generation of the trication or monocation species of aryl-substituted sumanene derivatives, and show some properties including the redox propertiy.

Preference of heavy fragments as competing modes for alpha decay of 294Og

Complete binary decay of [Formula: see text]Og formed in the heavy-ion fusion reaction is studied in the frame work of Yukawa-plus-exponential potential with a third-order polynomial potential for the overlapping region. Preformation probability, which is taken as the probability of penetration in the overlapping region, calculated for the use of reduced classical hydrodynamical mass, reveals the preference for near symmetric fission fragments [Formula: see text], [Formula: see text], in competency with alpha decay. Influence of the parameter [Formula: see text] of classical hydrodynamical mass is studied in preformation values. Half-life calculated for alpha decay matches well with experimental value for the use of reduced mass. Half-lives calculated for symmetric, near symmetric fragments [Formula: see text], [Formula: see text] are found to be low for the use of reduced hydrodynamical mass and promises preference of near symmetric fragments emission, as a competing decay mode to alpha decay and confirms the role of shell structure in deciding the most probable fragment.

Fusion cross section and total kinetic energy of fission fragments by the dynamical dissipative surface-friction model

The capture cross section, the fusion cross section, and the quasi-fission yield producing symmetric fragments ( ACN/2 ± 20u ) in the 48 Ca+ 238 U reaction are analyzed by the multidimensional Langevin equation taking account of the surface friction effect. From the experimental data, the strength of the tangential friction has been determined. It is presented that tangential friction increases in proportional to the power of the relative velocity of the projectile and the target.

Evolution of the shape of fission fragment energy spectrum with absorber thickness in two different media and effective charge correction

The energy loss behavior of fission fragments (FFs) from [Formula: see text]Cf(sf) in thin Mylar [Formula: see text] and Aluminium absorber foils has been revisited. The aim is to investigate the observed change in the well-known asymmetric energy of spontaneous fission of [Formula: see text]Cf as the fragments pass through increasingly thick absorber foils. Two different types of absorbers have been used: one elemental and the other an organic compound. The stopping powers have been determined as a function of energy for three fragment mass groups with average masses having [Formula: see text], 141.8, 125.8 corresponding to light, heavy and symmetric fragments of [Formula: see text]Cf. The energy loss data have been compared with the predictions of SRIM 2013 code. The best representations of the data have been achieved using the effective Z correction term in the stopping power relation from the classical Bohr theory. Using the effective charge (Z[Formula: see text]) in the stopping power relation in the classical Bohr theory best describes the stopping power data. Spectrum shape parameters, subsequently, have been extracted from the energy spectra of FFs for different foil thicknesses. The effective charge (Z[Formula: see text]) correction term determined from the stopping power data is then used in the simulation for the absorber thickness dependence of the shape parameters of the energy spectrum. The present simulation results are compared with the TRIM prediction. The trends of the absorber thickness dependence of the spectrum shape parameters, for both Mylar and Aluminium, are well reproduced with the present simulation.

Symmetrical patterns in natural images

One of the approaches to image analysis is based on the use of visual alphabets comprising the compact patterns characteristic of the images of a particular class. Elements of these alphabets can be either obtained from a theoretical model describing the basic image structures or extracted directly from the training sets. Symmetric patterns characteristic of the images of outdoor scenes were investigated in this study. The choice of this pattern class is driven by the fact that the objects of interest usually have at least local symmetry. Furthermore, selection of only symmetric patterns allows most fragments of random textures that in most cases do not have symmetry to be dismissed. The image set used in this study comprised 829 monochromatic photographs showing natural objects and textures at different scales. Fragments with diameters of 13 pixels having 1 of 9 symmetry types were selected from this set. The obtained sets of symmetric fragments were processed using a density-based spatial clustering of applications with noise (DBSCAN) cluster analysis algorithm, which allows clusters of arbitrary shape to be analyzed. Fifteen pattern types were obtained; five of them have not previously been used as elements of visual alphabets. Most of the obtained patterns have reflection symmetry, which agrees with the results of psychophysical studies, according to which reflection symmetry is identified faster than other symmetry types. The obtained data can be used for the formation of elements of visual alphabets as well as for synthesizing the stimuli for the experiments in the field of vision physiology.

Isomerization Dynamics in the Symmetric and Asymmetric Fragmentation of Ethane Dications.

Hydrogen- or proton-migration-induced isomerization has recently been of concern for its critical role in the dissociation of organic molecules of astrophysical or biological relevance. Herein we present a combined experimental and theoretical study of the two-body C-C bond breakdown dissociation of ethane dication. For the asymmetric fragmentation channel CH2+ + CH4+, the kinetic energy release measurements and ab initio quantum chemical calculations demonstrate that the reaction pathway involving hydrogen-migration-induced isomerization of [CH3-CH3]2+ to [CH2-CH4]2+ can be accessed via the lowest triplet state rather than the ground singlet state of ethane dication. Interestingly, it is found that a considerable proportion of the yield of symmetric fragmentation CH3+ + CH3+, which is usually considered from a direct Coulomb explosion and seemingly independent of isomerization, could come from the dissociation of ethane dication in the ground singlet state with the involvement of [CH3-CH3]2+ isomerization to intermediate [H2C(H2)CH2]2+ of the diborane-like double-bridged structure.

Effect of compact and elongated configurations on the spontaneous and induced fission of Fm isotopes

The spontaneous fission (SF) analysis of even mass $^{242\ensuremath{-}260}\mathrm{Fm}$ isotopes is carried out using a preformed cluster model based on quantum mechanical fragmentation theory. The deformation effects are included up to the quadrupole (${\ensuremath{\beta}}_{2}$) deformed nuclei with optimum orientations (${\ensuremath{\theta}}_{i}^{\mathrm{opt}.}$) leading to hot-compact (side-to-side) and cold-elongated (tip-to-tip) configurations. The spherical and hot-compact deformed configurations of decay fragments result in the symmetric fragment mass distributions for Fm isotopes; however, the symmetric peak gets sharper with an increase in the neutron ($N$) number of the parent nucleus. In the case of cold orientations, a transition from two-peaked (asymmetric fission) to three-peaked (multimodal fission) mass distribution is observed with an increase in the mass number of Fm. The SF half-lives (${T}_{1/2}^{\mathrm{SF}}$) are calculated using the neck-length parameter ($\mathrm{\ensuremath{\Delta}}R$) for $^{242\ensuremath{-}260}\mathrm{Fm}$ isotopes and compared with the experimental data. Besides this, the induced fission of Fm isotopes is studied within the dynamical cluster-decay model. The energy dependence of fission fragment mass distributions and the isotopic dependence is analyzed at energy range ${E}^{*}=5$--42 MeV. In addition, the role of temperature-dependent deformations in the fission dynamics is also explored.

Investigation of fusion probabilities in the reactions with Cr52,54, Ni64 , and Zn68 ions leading to the formation of Z=120 superheavy composite systems

Background: The formation of superheavy nuclei in fusion reactions is suppressed by a competing quasifission process. The competition between the formation of the compound nucleus and the quasifission depends strongly on the reaction entrance channel. Purpose: The investigation of fission and quasifission processes in the formation of Z=120 superheavy composite systems in the Cr52,54+Cm248 and Zn68+Th232 reactions, and their comparison with the Ni64+U238 reaction at energies in the vicinity of the Coulomb barrier. Methods: Mass-energy distributions of fissionlike fragments formed in the reactions Cr52,54+Cm248 and Zn68+Th232 at energies near the Coulomb barrier were measured using the double-arm time-of-flight spectrometer CORSET. Results: Capture cross sections for the reactions under investigation were measured. The most probable fragment masses and total kinetic energies as well as their variances in dependence on the interaction energy were studied for asymmetric and symmetric fragments. The fusion probabilities were estimated from the analysis of mass-energy distributions. Conclusions: The estimated fusion probability drops down by a factor of 103 in the Cr54+Cm248 reaction compared to the reactions of Ca48 ions with actinides. Among the studied reactions, the Cr54+Cm248 is the most favorable one for the production of the superheavy element with Z=120.1 MoreReceived 3 August 2020Accepted 2 September 2020DOI:https://doi.org/10.1103/PhysRevC.102.044605©2020 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasFissionLow & intermediate energy heavy-ion reactionsNuclear fusionPropertiesA ≥ 220Nuclear Physics

Fission partition a reflection of shell closures: Decay of 220,224U⁎ at eight excitation energies

Decay modes of the compound systems formed in 86Kr + 134,138Ba → 220,224U⁎ reactions at eight excitation energies have been compared to explore the influence of shell closures and excitation energy. The mass distributions of the cross-sections have been calculated for the two compound systems by keeping their excitation energies the same. The production cross-section for the light particles, intermediate mass fragments, symmetric and asymmetric fission fragments, total fission fragments, percentage of the cross-section for symmetric and asymmetric fission fragments, the ratio of the cross-sections of the symmetric and asymmetric fission fragments and fission barrier as a function of the incident energy have been compared. The range of the incident energy which corresponds to the high probability of the compound nucleus process has been obtained. Three angular momentum windows have been realized from the variation of the production cross-section for the light particles, intermediate mass fragments, fission fragments and the total fragments as a function of the angular momentum which correspond to the dominance of a reaction mechanism in that window. The shell closures have been reflected in the fission partition and weaken with the increase of the incident energy along with the loss of odd-even effects. The mode of the reaction depends upon the excitation energy and angular momentum of the compound system.

Bilateral Shoulder Pain - Baseball

HISTORY: A 14-year-old right handed baseball player presents with two and a half years of insidious-onset bilateral shoulder pain. The pain is generalized in both shoulders, but worse anteriorly and in the right shoulder. He has continued to play year-round at an elite level, but he had to stop pitching due to pain. His shoulders “catch” and pain is exacerbated with rapid movements. PHYSICAL EXAM: Examination in clinic demonstrated tenderness of the anterior and posterior humeral head on the right and anterior humeral head on the left. Range of motion is limited in extension, internal rotation, and external rotation, and is full in flexion and abduction. Strength is full in all ranges of motion with pain in abduction, internal and external rotation. Hawkins, O’Brien’s, and Crank tests are positive for pain. He is distally neurovascularly intact. DIFFERENTIAL DIAGNOSIS: 1. Labral tear 2. Proximal Humeral Epiphysiolysis 3. Synovial Osteochondromatosis 4. Dysplasia Epiphysealis Hemimelica TEST AND RESULTS::Bilateral shoulder radiograph: Abnormal rounded ossific densities anterior to the right humeral head and metaphysis. Similar pattern of ossification anterior to the left humeral head,which is less well-defined than that seen in the right shoulder.Bilateral shoulder MR without contrast: Bilateral symmetric irregularly-shaped osteochondral fragments within the anterior glenohumeral joint spaces with evidence of erosions of the humeral head.Bilateral shoulder CT without contrast: Bony irregularity along the medial, proximal aspect of both humeri with clustered ossicles adjacent to the bony irregularity. No evidence of free intra-articular bodies. FINAL/WORKING DIAGNOSIS: Bilateral Synovial Osteochondromatosis of the Shoulders TREATMENT AND OUTCOMES: 1.Referred for a surgical consult, where non-operative treatment was recommended. 2.Started in physical therapy (PT). 3.Continued full participation in sports despite pain. 4.10-15% improvement after 3 months of PT. 5.Currently travelling for the winter baseball season and continuing PT at a distant site.

Formation and Decay of the Composite System Z = 120 in Reactions with Heavy Ions at Energies Near the Coulomb Barrier

The mass, energy and angular distributions of binary fragments formed in the reactions 64Ni + 238U, 58Fe + 244Pu, 52Cr + 248Cm, 54Cr + 248Cm at energies near the Coulomb barrier have been measured. The analysis of energy distributions of the symmetric fragments with mass numbers $${{{{A}_{{{\text{CN}}}}}} \mathord{\left/ {\vphantom {{{{A}_{{{\text{CN}}}}}} 2}} \right. \kern-0em} 2} \pm 20$$ formed in these reactions have been applied to separate compound nucleus fission and quasi-fission. The estimated fusion probability for the reactions Cr, Fe, and Ni ions with actinide targets shows an exponential dependence on the mean fissility parameter of the system and shows also that reaction with Cr ions is more favorable for production of the super heavy element with Z = 120.

Modeling Systems Based on the Assessment of Weak Symmetry Breaking in Reconstructed Attractors

The paper proposes to use the research method for chaotic processes based on the identification of weak symmetry breaking of the restored attractor. It is shown how the calculations results can be used to identify systems. An algorithm for creating finite-difference models has been developed, including: calculating by numerical methods the necessary conditions for the existence of chaos, reconstructing an attractor in a time series, searching for symmetric attractor fragments under conditions of weak symmetry breaking, determining the form of nonlinearities, and parametric identification. The result of the algorithm is a system of finite-difference equations in the state space Criteria for assessing symmetry breaking based on estimates of the divergence of fragments of phase trajectories are introduced. The results of modeling systems with chaotic dynamics are presented.

МОДЕЛИРОВАНИЕ ВЗАИМОДЕЙСТВИЯ УДАРНОЙ ВОЛНЫ С ДЕФОРМИРУЕМЫМ ПРОНИЦАЕМЫМ ГРАНУЛИРОВАННЫМ СЛОЕМ

This article presents a mathematical model that describes, in a one-dimensional approximation, the interconnected processes of unsteady deformation of flat permeable granular layers. The model consists of solid particles and wave processes in pore and surrounding gas. The model is based on nonlinear equations of dynamics of two interpenetrating continua. As interfacial forces, drag forces are taken into account when gas flows around ball particles and friction forces. The numerical solution of the equations is carried out according to the modified scheme of S.K. Godunov, adapted to the problems of the dynamics of interpenetrating media. The contact surfaces of pure gas with the porous granular layer and pore gas are the surface of the fracture of porosity and permeability. The numerical implementation of contact conditions is based on the solution of the problem of disintegration of a gap at a jump in porosity. Solutions are obtained for the effects of plane shock waves on a deformable granular layer. We study the transformation of waves passing through an elastoplastic granular layer with and without taking into account changes in the permeability of the layer. When solving problems, the dependence of the change in the permeability of a layer on its compression is used, which is also obtained numerically when modeling the compression of symmetric fragments of granular layers in a spatial setting. Numerical studies of the processes of nonlinear interaction of shock waves with deformable permeable granular layers have shown that the parameters of transmitted and reflected waves substantially depend on the degree of compression of the granular layers. Assessment of the protective properties of permeable barriers when exposed to strong shock waves should be carried out taking into account changes in their permeability due to deformation.

Numerical modeling of nonlinear dynamic and static compression of the metal mesh

Simulation of elastoplastic compression of a symmetric fragment of a bundle of woven steel grids was carried out. The simulation was carried out under static and dynamic loading modes in ANSYS and ANSYS LS-DYNA computing systems. A porous mesh package is formed by overlaying the layers on top of each other while maintaining the directions of wires. Such a packet has a quasiperiodic structure; therefore, a certain symmetric fragment can be distinguished. The compression was carried out by a pair of absolutely rigid plates moving symmetrically towards each other. In the calculations, a multilinear plasticity model with isotropic hardening was used. The diagram of static deformation of the material was used which was obtained experimentally. The calculations were carried out according to the algorithm of a perfect symmetric contact of bodies without friction and with friction. The dynamic loading of a fragment of the mesh packet was carried out at a constant speed. The characteristics of the pulse and the loading rate correspond to those observed in previous experimental studies. The dynamic strain diagram was assumed to be similar to a static one with an increased yield strength. Calculations showed that in all loading modes there is a high level of internal stresses, and complex inhomogeneous stress-strain state. We investigated two factors that could cause differences in the behavior of the curves of deformation of a porous medium - the finite length of the acting pulse and the differences in the dynamic and static compression diagrams of the initial mesh material. The main influence on the dynamic behavior of a fragment of a porous packet of a steel mesh is exerted by the dynamic properties of the wire material. The strain curves of the porous fragment qualitatively change in accordance with the behavior observed in static and dynamic experiments. The final duration of the loading pulse and the friction between the wires for this type of mesh do not have a significant effect. The numerical dependences of the relative area of the normal and lateral through sections of the symmetric fragment of the grid packet on the compression deformation are obtained.

Across barrier fission analysis of At⁎ isotopes formed in 3,4,6,8He+209Bi reactions

The fission decay mechanism of various 212,213,215,217At⁎ isotopes formed in tightly (3,4He) and loosely bound (6,8He) projectile induced reactions on 209Bi target, is studied within the framework of dynamical cluster-decay model (DCM), over a wide range of excitation energies spread across the Coulomb barrier. By optimizing appropriate neck-length parameter ΔR, the fission cross-sections are calculated for 212,213,215At⁎ compound nuclei (CN) at above barrier energies, where some experimental data is available. The DCM calculations are extended at below barrier region for these nuclei, and for one more reaction 8He+209Bi→217At⁎, using the systematics of 212,213,215At⁎ isotopes. The magnitude of fission cross-sections increase with the addition of neutrons in the He-projectile (or say in the At compound nucleus since the target nucleus of each reaction is same). To obtain better description of fission dynamics involved for neutron-deficient and neutron-rich He-induced reactions, the fragmentation potential and prefromation probability P0 of decaying fragments are analyzed along with corresponding barrier tunneling probability P. The fission fragment mass distributions are explored for all ‘At’ isotopes, and most probable fission fragments are identified. It has been observed that asymmetric fission forms the predominant decay mode for all isotopes, although a minor hump with very small preformation factor appears around symmetric fragments for lighter 212,213At⁎ nuclei. Finally, the N/Z dependence of fission cross-sections and most probable decaying fragments is explored in view of fragmentation structure and related cross-sectional yields.

Fission mass distribution of various superheavy nuclei and related dynamical analysis

The fission mass distribution of Z=104-120 superheavy nuclei formed in 238U-induced reactions is investigated using the dynamical cluster decay approach. The cross-section for the formation of symmetric fragments with masses A2±20 of 274Hs⁎, 286Cn⁎, 286Fl⁎, and 302120⁎ nuclei are calculated over a wide energy spectrum by rationalizing the neck-length parameter (ΔR). The calculations are carried out by including the quadrupole (β2i)-deformation of the fragments using hot and cold optimum orientation approaches. Within hot orientation criteria, symmetric fission distribution is observed for 274Hs⁎ nucleus which becomes highly asymmetric in nature for 302120⁎ compound system. The lead (Pb)-peaks originating due to quasi-fission process start competing while going from 274Hs⁎ to 302120⁎ nucleus. Additionally, the role of cold orientation approach is also explored for these nuclei which show the opposite trend in the mass distribution while going from Z=108 to Z=120 superheavy system. Further, the fission and asymmetric quasi-fission cross-sections are predicted for various entrance channels i.e. 58Fe+244Pu, 54Cr+248Cm, and 50Ti+249Cf and compared with experimentally available data of 64Ni+238U reaction to identify the favorable projectile-target combination for the synthesis of Z=120 nucleus. The results show that because of larger fusion probability, 50Ti+249Cf reaction seems to provide a favorable option for the synthesis of Z=120 superheavy nucleus.

2.2]Paracyclophane bis(pyridine)-based metallosupramolecular rhombs in the gas phase: Competitive cleavage of non-covalent and weak covalent bonds.

The gas-phase fragmentation behavior of self-assembled metallo-supramolecular rhombs based on an unusual chiral [2.2]paracyclophane bis(pyridine) ligand is studied by collision-induced dissociation mass spectrometry. The fragmentation patterns strongly depend on the charge state of the respective mass-selected aggregate. For the doubly charged ions, simple symmetric fragmentation is observed in full accordance with previous results reported for related metallo-supramolecular species. The triply charged species cleaves unsymmetrically which can be rationalized by a preferred formation of ions with low charge density. CID of the quadruply charged rhomb reveals a complex fragmentation. Besides ligand oxidation to the radical cation, facile cleavage of the central covalently bound part of the [2.2]paracyclophane ligand takes place which is even preferred over rupture of the weak dative pyridine-Pd bond.

Fission and quasifission of the composite system Z=114 formed in heavy-ion reactions at energies near the Coulomb barrier

Background: Study of competition between compound nucleus fission and quasifission in heavy-ion-induced reactions and its dependence on the reaction entrance channel are important for picking up the right target-projectile combination for the synthesis of superheavy elements.Purpose: We investigate the decrease of fusion probability in the $^{52}\mathrm{Cr}+^{232}\mathrm{Th}$ reaction in comparison with that in the reactions $^{48}\mathrm{Ca}+^{244}\mathrm{Pu}$ and $^{48}\mathrm{Ti}+^{238}\mathrm{U}$. All reactions lead to the formation of composite systems with $Z=114$.Methods: Mass-energy distributions of binary fragments formed in the reaction $^{52}\mathrm{Cr}+^{232}\mathrm{Th}$ leading to the $^{284}\mathrm{Fl}$ composite system at energies of 265, 288, 302, and 320 MeV have been measured using the double-arm time-of-flight spectrometer CORSET. To study the properties and entrance channel dependence of quasifission in more detail, the mass and energy distributions of fragments formed in the $^{86}\mathrm{Kr}+^{198}\mathrm{Pt}$ reaction, leading to the same composite system $^{284}\mathrm{Fl}$, have also been measured.Results: The contribution of symmetric fragments in all fissionlike events is nearly the same for both the reactions $^{48}\mathrm{Ti}+^{238}\mathrm{U}$ and $^{52}\mathrm{Cr}+^{232}\mathrm{Th}$ at energies above the barrier, while it is greater for $^{48}\mathrm{Ca}+^{244}\mathrm{Pu}$. The analysis of total kinetic energy distribution of symmetric fragments formed in the reaction $^{52}\mathrm{Cr}+^{232}\mathrm{Th}$ shows that at an energy 15% over the Bass barrier the contribution of compound nucleus fission in the capture cross section is less than 0.4%.Conclusions: The fusion probability drops down by about a factor of 4 at the transition from the $^{48}\mathrm{Ca}+^{244}\mathrm{Pu}$ reaction to $^{48}\mathrm{Ti}+^{238}\mathrm{U}$ and about a factor of 25 at the transition to $^{52}\mathrm{Cr}+^{232}\mathrm{Th}$ at energies above the barrier. It agrees with the trend of fusion probability to decrease exponentially with increasing the mean fissility parameter of the composite system.