Fusion-evaporation Cross Sections Research Articles

Measurement of fusion-evaporation cross sections for reactions of Ca44 with Gd154,156,157,160 targets

Background: Previously reported fusion-evaporation cross sections of residues in $^{45}\mathrm{Sc}$-induced reactions with lanthanide targets are much smaller than $^{48}\mathrm{Ca}$-induced reactions on the same targets. $^{44}\mathrm{Ca}$ is one proton removed from $^{45}\mathrm{Sc}$ and could be used to produce nuclei with a relative neutron content between those produced in the $^{45}\text{Sc-}$ and $^{48}\mathrm{Ca}$-induced reactions.Purpose: Several experiments worldwide have attempted to discover elements beyond the currently heaviest known element, oganesson ($Z=118$). Due to a lack of appropriate targets, these efforts focused on projectiles other than $^{48}\mathrm{Ca}$, which has been widely used for a number of successful element discovery experiments. The present study continues our previous work to understand the influence of various projectiles on the compound nucleus in fusion-evaporation reactions, and addresses the influence of target neutron number on fusion-evaporation cross sections.Methods: In experiments performed at the Cyclotron Institute at Texas A University, a beam of $^{44}\mathrm{Ca}^{6+}$ with an energy of $\ensuremath{\approx}5\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}/u$ was delivered by the K500 superconducting cyclotron to the Momentum Achromat Recoil Spectrometer (MARS). The $^{44}\mathrm{Ca}$ projectiles bombarded various isotopically enriched Gd targets in the MARS target chamber to create evaporation residues, which were spatially separated from unreacted projectiles by MARS and identified via their characteristic $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{decay}$ energies. Excitation functions for the reactions of $^{44}\mathrm{Ca}$ with $^{154,156,157,160}\mathrm{Gd}$ were measured at several projectile energies each.Results: The maximum $4n$ cross sections in the $^{44}\mathrm{Ca}{+}^{154,156,157,160}\mathrm{Gd}$ reactions were $0.038\ifmmode\pm\else\textpm\fi{}0.008, 0.83\ifmmode\pm\else\textpm\fi{}0.08, 3.8\ifmmode\pm\else\textpm\fi{}0.2$, and $3.0\ifmmode\pm\else\textpm\fi{}0.5$ mb, respectively. Production cross sections for the more neutron-rich targets were surprisingly constant even given the substantial changes in the difference in neutron binding energy and fission barrier of the compound nuclei.Conclusions: Collective enhancements to level density caused a reduction in compound nucleus survivability for all targets. While this effect was required to obtain good agreement between theoretical calculations and experimental data, it was not sufficient to explain the cross sections for the reaction with the most neutron-deficient target studied $(^{154}\mathrm{Gd})$. Instead, it appears that the difference in the fission barrier and neutron binding energy is the dominant factor affecting the survival of the compound nucleus in this case.

The influence of the nuclear matter incompressibility on heavy-ion fusion reactions at near- and above-barrier energies

Based on simulating the saturation property of cold nuclear matter for complete fusion channel of two approaching nuclei, we systematically investigate the role of nuclear incompressibility in the nucleus-nucleus potential and fusion-evaporation cross section of 69 medium-heavy and heavy mass systems with 208≤Z1Z2≤1520. Our observations based on the uncoupled single-barrier potential model and the M3Y double-folding potential which is corrected with a repulsive core term reveal that the incompressibility of cold nuclear matter can be responsible for the discrepancy between the measured and calculated values of the fusion cross sections at energies around and above the Coulomb barrier. In other words, one can find that the high energy fusion cross sections can not be reproduced using the standard form of the M3Y-DF potential model without considering the repulsive core effects. We show that the strength of the repulsive contact term and also the incompressibility of the compound nuclei exhibit systematic behaviors with respect to the atomic and mass numbers of reacting nuclei. It is shown that the hardness level of nuclear matter reduces when one passes from lighter to heavier systems.

Fusion reactions around the barrier for Be+238U * *Supported by the National Natural Science Foundation of China (12005314, 11805289, 11875328, 11775316), and the ELI-NP Phase II, a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund - the Competitiveness Operational Programme (1/07.07.2016, COP, ID 1334)

Fusion-evaporation cross sections of U( Be, 5n) Cm are measured over a wide energy range around the Coulomb barrier. These measured cross sections are compared with model calculations using two codes, namely HIVAP2 and KEWPIE2. HIVAP2 calculations overestimate the measured fusion-evaporation cross sections by a factor of approximately 3. In KEWPIE2 calculations, two approaches, namely the Wentzel-Kramers-Brillouin (WKB) approximation and the empirical barrier-distribution (EBD) method, are used for the capture probability; both of them properly describe the measured cross sections. Additionally, fusion cross sections of Be+ U measured in two experiments are applied to constrain model calculations further through three codes, i.e., HIVAP2, KEWPIE2, and CCFULL. Parameters in these codes are also examined by comparison with measured fusion cross sections. All the comparisons indicate that the KEWPIE2 calculations using the WKB approximation agree well with the measured cross sections of both fusion reactions Be+ U and the fusion-evaporation reaction U( Be, 5n) Cm. Calculations using the fusion code CCFULL are also in good agreement with the measured fusion cross sections of Be+ U.

Dynamical aspects of Ti48+Fe58,Ni58→Cd*106,Sn*106 reactions at energies near the Coulomb barrier

The study of the heavy-ion reactions at the near- and sub-barrier regimes gives immense information about the nuclear structure and the involved reaction dynamics. It has been observed that a slight difference in the nuclear structure may lead to a significant change in the sub-barrier fusion excitation functions. The studies of different trends of excitation functions below the Coulomb barrier region due to dissimilar structures of the nuclei, which are involved in the reaction, are available in literature. To understand the role of different structures and dynamics involved in such reactions, an investigation of $^{48}\mathrm{Ti}$-induced reactions on $^{58}\mathrm{Fe}$ and $^{58}\mathrm{Ni}$ forming $^{106}\mathrm{Cd}^{*}$ and $^{106}\mathrm{Sn}^{*}$ compound nuclei (CN), respectively, has been made at similar ${E}_{\mathrm{c}.\mathrm{m}.}/{V}_{b}$ values within the framework of the dynamical cluster decay model (DCM). The difference in the structure between the nuclei is quite notable with $^{58}\mathrm{Ni}$ and $^{106}\mathrm{Sn}^{*}$ having a proton shell closure ($Z=28$ and 50, respectively). Within the DCM, the experimental fusion evaporation cross sections are reproduced using deformed configurations effects included up to quadruple deformations (${\ensuremath{\beta}}_{2i}$) for two nuclei having optimum orientations ${\ensuremath{\theta}}^{\mathrm{opt}.}$. The fusion evaporation data at near- and sub-barriers has been explained through the calculated enhanced $\mathrm{\ensuremath{\Sigma}}{P}_{0}$ values of the decaying channels in the case of $^{106}\mathrm{Cd}^{*}$ in comparison to $^{106}\mathrm{Sn}^{*}$. Moreover, it is observed that the quantum tunneling of the fragments is less hindered in the case of $^{106}\mathrm{Cd}^{*}$ as compared to $^{106}\mathrm{Sn}^{*}$ at the lower values of ${E}_{\mathrm{c}.\mathrm{m}.}/{V}_{b}$, i.e., having less barrier modification ($\mathrm{\ensuremath{\Delta}}{V}_{B}$) in the case of the former. The role of magicity has been further explored with the plotted values of the ratio of fusion cross sections (${\ensuremath{\sigma}}_{\mathrm{fus}}$) of CN $^{106}\mathrm{Sn}^{*}$ and $^{112}\mathrm{Xe}^{*}$ (formed in the reaction with both the projectile $^{58}\mathrm{Ni}$ and target $^{54}\mathrm{Fe}$ having proton and neutron magicity, respectively) with respect to $^{106}\mathrm{Cd}^{*}$, which are highly suppressed in the case of the latter in comparison to the former, particularly, below the Coulomb barrier.

Fragmentation analysis of 105Ag∗ nucleus governed via complete and incomplete fusion channels at Ec.m. = 89MeV

A systematic study of dynamical aspects associated with heavy-ion-induced [Formula: see text] reaction is carried out at center-of-mass energy [Formula: see text] MeV. The complete fusion (CF) and incomplete fusion (ICF) contributions are estimated by using the dynamical cluster-decay model (DCM). The incomplete fusion component is examined by normalizing the incident beam energy for each of the breakup fragment. The fusion evaporation cross-sections that emerged from CF and ICF channels are duly addressed using the optimized value of neck-length parameter [Formula: see text]. Further, the mass yield of compound nuclei (CN) formed in the CF and ICF processes is analyzed with respect to angular momentum [Formula: see text] values. The DCM-based calculations indicate the possible contribution of deep inelastic collision (DIC) in the decay of [Formula: see text] at higher [Formula: see text] values, and DIC cross-sections are predicted which call for future validation.

Isospin influence on fragments production in 78Kr + 40Ca and 86Kr + 48Ca collisions at 10 MeV/nucleon

In heavy ion collisions at low energy (E/A < 10–15 MeV/nucleon) the N/Z ratio in the entrance channel is closely related to the isospin degree of freedom and can influence the reaction mechanisms and consequently the production of the fragments in the exit channel. We analyse the fragment production cross sections in the reactions 86Kr + 48Ca and 78Kr + 40Ca , at the laboratory energy of 10 MeV/nucleon. The experiment was conducted at the INFN Laboratori Nazionali del Sud in Catania, by using the \( 4\pi\) detector CHIMERA. For the two reactions, elastic scattering measurements are performed to extract the normalization factor used to evaluate the absolute cross sections. Velocity and energy spectra, mass and charge distributions, as well as dynamic features of reaction products, are studied. The study of the characteristics of mass and charge distributions, energy and velocity spectra of the reaction products shows mainly a relaxed component, related to fusion reaction followed by evaporation or binary decay. Nevertheless signals ascribable to a non equilibrated component are present. Structure effects are evident in the staggered shape of emitted fragments cross sections and are more pronounced in the neutron poor system. The analysis highlights clear differences for the two systems in the contributions arising from different reaction mechanisms. Besides, a study of the overall influence from the entrance channel energy is performed. Comparisons to DNS (DiNuclear System) and GEMINI++ models are reported. The data analysis indicates a slightly higher fusion-evaporation cross section and a strongly pronounced probability of fission-like processes for the neutron poor system with respect to the neutron rich one. The neutron enrichment seems thus to limit the formation of the composite system and to inhibit the fission decay channel.

Fusion probability of massive nuclei in reactions leading to heavy composite nuclear systems

Reactions between massive nuclei show a considerable reduction in fusion-evaporation cross-sections at the Coulomb barrier according to the comparison of experimental values with those calculated by barrier passing (BP) and statistical model (SM) approximations. Reduced fusion cross-sections corresponding to fusion probability PCN&lt;1 are accompanied by a high probability of deep-inelastic and quasi-fission processes arising on the way to fusion. At the same time, the excitation functions for evaporation residues (ERs) obtained in very mass-asymmetric projectile-target combinations are well described in the framework of the BP model (assuming PCN=1) and SM approximations. In the framework of SM, the survivability of produced heavy nuclei can be described with the use of adjusted macroscopic fission barriers. Fusion suppression appears in less asymmetric combinations, for which PCN values can be estimated using survivability obtained for very asymmetric ones leading to the same CN. An attempt was made to systemize the PCN data derived from different projectile-target combinations leading to ERs in the range from Pb to the most heavies, which are compared withPCN values obtained in fission experiments.

Isotopic trends of quasifission and fusion-fission in the reactions Ca48+Pu239,244

Background: Quasifission and fusion-fission are primary mechanisms to prevent the production of superheavy elements. The recent experimental measurements reveal that the fusion-evaporation cross section in the $3n$ reaction channel of $^{48}$Ca+$^{239}$Pu is 50 times lower than using $^{244}$Pu as target nucleus. However, the precise mechanisms of this remarkable isotopic dependence are not well understood. Purpose: To understand the experimental observation of the rapid decrease of stability of superheavy nuclei as the neutron number decreases, the theoretical studies of quasifission and fusion-fission in connection with experimental production for $Z$=114 flerovium isotopes are required to investigate the possible differences in reaction mechanisms induced by these two targets. Methods: We propose an approach called TDHF+HIVAP to take into account both the evolution of dinuclear system and the deexcitation of compound nucleus, which combines the microscopic time-dependent Hartree-Fock (TDHF) method for the fusion and quasifission dynamics with the statistical evaporation model HIVAP for fusion-fission dynamics. Results: ......The quantum shell effect displays a crucial role in both the quasifission and the fusion-fission processes. The quasifission is considerably reduced and the survival probability is enhanced around one order of magnitude in the reaction using $^{244}$Pu target as compared to the $^{239}$Pu case. Conclusions: The studies by using TDHF+HIVAP method well account for the experimental observations and the present method clearly shows its applicability in the reaction mechanisms of quasifission and fusion-fission dynamics. The experimental and theoretical results encourage the use of neutron-rich targets for the production of new superheavy elements.

Role of shell and pairing correction in the dynamics of compound nuclei with ACN = 118–196 using collective clusterization approach

Shell and pairing correction are known to significantly affect the binding energy of a nucleus. In the present work, the effect of shell correction and pairing energy on the fusion-evaporation cross sections (σER) and the reaction dynamics of five different hot and rotating compound systems 118Xe⁎, 128Ce⁎, 146Sm⁎, 172Yb⁎, and 196Pt⁎ formed via respective entrance channels namely Si28+Zr90 (ηi=0.525), S32+Mo96 (ηi=0.5), 36S + 110Pd (ηi=0.506), 124Sn + 48Ca (ηi=0.442) and 132Sn + 64Ni (ηi=0.346) (ηi represents the entrance channel mass asymmetry) is studied within the collective clusterization approach. The basis of choosing these reactions is to keep entrance channel mass asymmetry in such a way that the temperature (T) of the compound systems lie in the common range of 1.6 MeV to 1.9 MeV corresponding to the available experimental data. It is observed that the magnitude of fragmentation potential and preformation probability of decaying fragments is influenced with the inclusion of shell correction and pairing energy, while the overall decay pattern remains unaffected except that, few fragments minimized in energy correspond to different atomic (Z)-number compared to the case when the shell and pairing correction is not taken into account. The change of magnitude ultimately modifies the fusion-evaporation cross sections of the compound systems. The effect is more pronounced at the lower temperature or below barrier incident energies. The pairing energy has a relatively lesser influence on the considered observables as compared to the shell correction term. The order of sequence in which the shell and pairing energy is switched off leaves the decay structure unaltered, however the fusion-evaporation cross sections are influenced significantly if the charge of evaporation residue (ER) gets changed.

Evaluation of fusion-evaporation cross-section calculations

Calculated fusion-evaporation cross sections from five different codes are compared to experimental data. The present comparison extents over a large range of nuclei and isotopic chains to investigate the evolution of experimental and calculated cross sections. All models more or less overestimate the experimental cross sections. We found reasonable agreement by using the geometrical average of the five model calculations and dividing the average by a factor of 11.2. More refined analyses are made for example for the 100Sn region.

Hot fusion-evaporation cross sections ofCa44-induced reactions with lanthanide targets

Hot fusion-evaporation cross sections of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ca</mml:mi><mml:mprescripts /><mml:none /><mml:mn>44</mml:mn></mml:mmultiscripts></mml:math>-induced reactions with lanthanide targets

Hot fusion-evaporation cross sections ofSc45-induced reactions with lanthanide targets

Hot fusion-evaporation cross sections of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mmultiscripts><mml:mi>Sc</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>45</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>-induced reactions with lanthanide targets

Experiments on the synthesis of superheavy nucleiFl284andFl285in thePu239,240+Ca48reactions

Irradiations of $^{239}\mathrm{Pu}$ and $^{240}\mathrm{Pu}$ targets with $^{48}\mathrm{Ca}$ beams aimed at the synthesis of $Z=114$ flerovium isotopes were performed at the Dubna Gas Filled Recoil Separator. A new spontaneously fissioning (SF) isotope $^{284}\mathrm{Fl}$ was produced for the first time in the $^{240}\mathrm{Pu}+^{48}\mathrm{Ca}$ (250 MeV) and $^{239}\mathrm{Pu}+^{48}\mathrm{Ca}$ (245 MeV) reactions. The cross section of the $^{239}\mathrm{Pu}(^{48}\mathrm{Ca},3n)^{284}\mathrm{Fl}$ reaction channel was about 20 times lower than predicted by theoretical models and about 50 times lower than the maximum fusion-evaporation cross section for the $3n$ and $4n$ channels measured in the $^{244}\mathrm{Pu}+^{48}\mathrm{Ca}$ reaction. In the $^{240}\mathrm{Pu}+^{48}\mathrm{Ca}$ experiment, performed at 245 MeV in order to maximize the $3n$-evaporation channel, three decay chains of $^{285}\mathrm{Fl}$ were detected. The $\ensuremath{\alpha}$-decay energy of $^{285}\mathrm{Fl}$ was measured for the first time and decay properties of its descendants $^{281}\mathrm{Cn}, ^{277}\mathrm{Ds}, ^{273}\mathrm{Hs}, ^{269}\mathrm{Sg}$, and $^{265}\mathrm{Rf}$ were determined with higher accuracy. The assignment of SF events observed during the irradiation of the $^{240}\mathrm{Pu}$ target with a 250 MeV $^{48}\mathrm{Ca}$ beam to $^{284}\mathrm{Fl}$ decay is presented and discussed. The cross sections at both $^{48}\mathrm{Ca}$ energies are similar and exceed that observed in the reaction with the lighter isotope $^{239}\mathrm{Pu}$ by a factor of 10. The decay properties of the synthesized nuclei and their production cross sections indicate a rapid decrease of stability of superheavy nuclei as the neutron number decreases from the predicted magic neutron number $N=184$.

Production of evaporation residues in the vicinity of the N =126 closure

The shell structure and fission-barrier heights of nuclei involved in the compound- nucleus (CN) de-excitation chains leading to observable evaporation residues (ER) determine essentially fusion-evaporation cross sections for heavy fissile nuclei produced in the vicinity of the N=126 neutron shell in heavy ion (HI) reactions. The entrance-channel effect of quasifission (QF) lowering the fusion cross section in reactions with massive nuclei and the effect of the collective enhancement in the nuclear level density (CENLD), corresponding to the exit channel, should strongly reduce production cross sections for ER and increase the observed fission cross section in the vicinity of N=126. These effects were not evidently manifested in the analysis of cross sections obtained in different CN reactions leading to Po isotopes produced in a wide region of N. This analysis has been performed in the framework of standard statistical model (SSM) approximations. As a whole, production cross sections for neutron deficient Po nuclei produced in HI reactions can be reproduced in the framework of SSM with the reduced liquid-drop fission barriers [1]. We present a similar analysis of ER and fission cross section data obtained in the reactions induced by 3,4He on Pb and Bi targets, which lead to Po and At compound nuclei [2], which proved to be a good test of the preceding results [1]. Such reactions are characterized by much lower angular momenta transferred to a CN that allows to suggest more pronounced manifestation of CENLD effects in the CN decay. These reactions also do not reveal any indications of QF. This simplifies the data analysis and makes it more unambiguous. The results of the analysis of the 3,4He reactions performed in the present work demonstrate the same changes in the fission barrier heights for Po and At nuclei as obtained earlier with HI reactions data [1].

Towards a unified description of evaporation-residue fusion cross-sections above the barrier

A meticulous study of nearly 300 fusion-evaporation cross-section data reveals that, when properly scaled, fusion excitation function complies with a universal homographic law which is, within experimental errors, reaction system independent. From such complete and summed complete and incomplete fusion excitation functions are extracted the limiting energy for the complete fusion and the main characteristics (onset, maximum and vanishing) of the incomplete fusion. The DYWAN microscopic transport model correctly predicts the incomplete fusion cross-section for incident energies and suggests that the nuclear transparency is at the origin of fusion disappearance.

Compound nucleus evaporative decay as a probe for the isospin dependence of the level density

The evaporative decay of the compound nucleus 139Eu produced by the 180MeV 32S + 107Ag reaction was studied with the aim to test the empirical isospin expressions of the level density, recently appeared in the literature. We measured light charged particle spectra and angular correlations in coincidence with the evaporation residues and the invariant velocity distribution of the evaporation residues. In addition, an independent experiment was performed on the reaction 32S + 109Ag at the same incident energy. Evaporation residue angular distribution was measured and the fusion-evaporation cross-section was determined. All the measured quantities are compared with the predictions of different level density prescriptions: a) isospin independence, b) a dependence from N - Z and c) a dependence from Z-Z0 as proposed by Al-Quraishi et al. Results show that the predictions of the Z-Z0 dependence are far off the experimental data for all the measured observables. Regarding the isospin independent prescription and the N - Z dependence, although no great differences appear between their predictions the N - Z prescription seems to better describe the experimental data.

Barrier modification in sub-barrier fusion reaction 64Ni+100Mo using Wong formula with Skyrme forces in semiclassical formalism

We obtain the nuclear proximity potential by using semiclassical extended Thomas Fermi (ETF) approach in Skyrme energy density formalism (SEDF), and use it in the extended ℓ-summed Wong formula under frozen density approximation. This method has the advantage of allowing the use of different Skyrme forces, giving different barriers. Thus, for a given reaction, we could choose a Skyrme force with proper barrier characteristics, not-requiring extra "barrier lowering" or "barrier narrowing" for a best fit to data. For the 64Ni+100Mo reaction, the ℓ-summed Wong formula, with effects of deformations and orientations of nuclei included, fits the fusion-evaporation cross section data exactly for the force GSkI, requiring additional barrier modifications for forces SIII and SV. However, the same for other similar reactions, like 58,64Ni+58,64Ni, fit the data best for SIII force. Hence, the barrier modification effects in ℓ-summed Wong expression depend on the choice of Skyrme force in semiclassical ETF method.

Fusion reaction cross-sections using the Wong model within Skyrme energy density based semiclassical extended Thomas Fermi approach

First, the nuclear proximity potential, obtained by using the semiclassical extended Thomas Fermi (ETF) approach in Skyrme energy density formalism (SEDF), is shown to give more realistic barriers in frozen density approximation, as compared to the sudden approximation. Then, taking advantage of the fact that, in ETF method, different Skyrme forces give different barriers (height, position and curvature), we use the l-summed extended-Wong model of Gupta and collaborators (2009) [1] under frozen densities approximation for calculating the cross-sections, where the Skyrme force is chosen with proper barrier characteristics, not-requiring additional “barrier modification” effects (lowering or narrowing, etc.), for a best fit to data at sub-barrier energies. The method is applied to capture cross-section data from 48Ca + 238U, 244Pu, and 248Cm reactions and to fusion–evaporation cross-sections from 58Ni + 58Ni, 64Ni + 64Ni, and 64Ni + 100Mo reactions, with effects of deformations and orientations of nuclei included, wherever required. Interestingly, whereas the capture cross-sections in Ca-induced reactions could be fitted to any force, such as SIII, SV and GSkI, by allowing a small change of couple of units in deduced lmax-values at below-barrier energies, the near-barrier data point of 48Ca + 248Cm reaction could not be fitted to lmax-values deduced for below-barrier energies, calling for a check of data. On the other hand, the fusion–evaporation cross-sections in Ni-induced reactions at sub-barrier energies required different Skyrme forces, representing “modifications of the barrier”, for the best fit to data at all incident center-of-mass energies Ec.m.ʼs, displaying a kind of fusion hindrance at sub-barrier energies. This barrier modification effect is taken into care here by using different Skyrme forces for reactions belonging to different regions of the periodic table. Note that more than one Skyrme force (with identical barrier characteristics) could equally well fit the same data.

Fusion hindrance forAl27+Sc45and other systems with a positiveQvalue

Fusion evaporation cross sections for the {sup 27}Al+{sup 45}Sc (Q=9.63 MeV) system are measured down to about 300 nb. Deviations from standard coupled-channels calculations were observed in this system at the lowest energies. The steep fall-off of the fusion cross sections can be reproduced by calculations using a shallow potential model, which was originally developed to explain the hindrance behavior of heavy-ion fusion in medium-mass systems with negative Q values. Comparisons of the hindrance behavior between the present experiment and other systems, for example, {sup 28}Si+{sup 30}Si (Q=14.3 MeV) and {sup 36}S+{sup 48}Ca (Q=7.55 MeV) are presented.

Dynamical cluster-decay model for fusion cross-sections below the barrier

Fusion-evaporation cross-sections σ e v r , in reactions known for fusion hindrance phenomenon in coupled-channels calculations at below barrier energies, are studied in terms of the dynamical cluster-decay model (DCM) and the Wong formula, both based on proximity potential, by using the concept of “barrier modification” at sub-barrier energies, first advocated by Misicu and Esbensen for M3Y potential. The DCM is shown to contain the “barrier lowering” property as its inbuilt characteristic, and the same is shown possible empirically in ( ℓ-summed) Wong formula.