Quantum Mechanical Fragmentation Theory Research Articles

Exploring fission and quasi-fission in 31Al + 197Au: probing energies near and beyond Coulomb barrier

An idea to understand the fragmentation of a formed nuclear entity (i.e. compound nucleus), induced via heavy-ion reactions, is an interesting task especially at incident energies near, above and far away from the Coulomb barrier. In the present work, we are studying the decay dynamics of a formed nuclear entity i.e. 228U* compound nucleus (CN), via the radioactive beam of Aluminium-31 (31Al) striking on the stable Gold-197 (197Au) target nucleus, for incident energies E c.m. = 106.2–163.2 MeV. A comprehensive knowledge regarding the probable decaying fragments from 228U* has been accumulated using the collective clusterization approach of the Dynamical Cluster-decay Model (DCM) in terms of mass and charge dispersion, which built up on the Quantum Mechanical Fragmentation Theory (QMFT). Through both of these dispersion cases, we have identified the decaying fragments in the fission and heavy-mass regions, at different scale of incident energies. Further, the fission cross-sections ( σfisTheo ) have been obtained for 31Al + 197Au → 228U* reaction at the above said E c.m. (MeV) and compared with the experimental data. This study has been carried out using two different sets of Skyrme force parameters (SIII and SSk), which are employed within the semiclassical approach of Skyrme Energy Density Formalism. Unlike for energies below and near the barrier, a significant difference has been observed between calculated ( σfisTheo ) and experimental ( σfisExpt ) cross-sections for above barrier energies, with independent choice of Skyrme forces. Such discrepancy noticed has been addressed with the presence of quasi-fission (QF) event. Similar phenomena has also been seen for 19F-induced reaction forming the same CN (228U*).

Sequential decay analysis of $^{235}$U(n$^{th}$,f) reaction using fragmentation approach

Abstract Numerous experimental and theoretical observations conclude that the probability of the three fragment emission (ternary fission) or the binary fission increases when one proceeds towards the heavy mass region of nuclear periodic table. The collinear cluster tripartition (CCT) channel of $^{235}$U(n$^{th}$,f) reaction is studied and it was observed that the CCT may be a sequential process or a simultaneous emission phenomena. Till now, different approaches are introduced to study the CCT process as a simultaneous process or sequential process, but the decay dynamics of these modes is not fully explored. It will be of interest to identify the three fragments of the sequential process and to explore their related dynamics using some excitation energy dependent approach. Hence, in present work, an attempt is made to study the sequential decay mechanism of $^{235}$U(n$^{th}$,f) reaction using quantum mechanical fragmentation theory (QMFT). The decay mechanism is considered in two steps, where initially the nucleus splits into an asymmetric channel. In the second step, the heavy fragment obtained in the first step divides into two fragments. Stage I analysis is done by calculating the fragmentation potential and the preformation probability for the spherical and deformed choice of the decaying fragments. The most probable fragment combination of stage I are identified in view the dips in the fragmentation structure, and the corresponding maxima's of the preformation probability ($P_0$). The excitation energy of the decay channel is calculated using an iteration process. The obtained excitation energy of the identified heavy fragments is further used for the fragmentation analysis, and the subsequent binary fragments of the sequential process are obtained. The identified three fragments of the sequential process are in agreement with the experimental observation and are found nearby the neutron or proton shell closure. Finally, the kinetic energy of the observed fragments is calculated and the middle fragment of the CCT mechanism is identified.

Implication of compact configuration of hexadecapole deformed actinides in the synthesis of superheavy nuclei

The quadrupole (β2) deformed targets in the actinide region are found to be of great relevance in the production of superheavy nuclei (SHN), in the compact fusion mechanism. Recently, the application of “elongated” and “compact” configurations of pear-shape octupole (up to β3) deformed nuclei was found to play a significant role in the fusion-fission dynamics of heavy-ion induced reactions. In the present work, we intend to explore the relevance of higher-order deformed (up to β4) actinides and their compact configuration in the production cross-section as well as de-excitation of SHN (dynamics of 48Ca + 238U →286Cn∗ → A1 + A2 reaction). For the above analysis, we have calculated σER within the framework of dynamical cluster-decay model developed on the basis of quantum mechanical fragmentation theory, which has been extended with the inclusion of deformations up to β4 and corresponding compact optimum orientation. Besides, on the basis of this theory, the fragmentation structure of 286Cn∗ superheavy nucleus is examined in terms of fragmentation potential (Vη) and preformation probability (P0) as a function of fragment mass number.

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.

Fission decay modes of 254Fm* compound nucleus formed in 16O+238U reaction

The quantum mechanical fragmentation theory (QMFT) based dynamical cluster-decay model (DCM) is applied to analyze the probable fission decay modes of 254Fm* compound nucleus produced in 16O+238U nuclear reaction at excitation energy EC*N =45.9 MeV. The fission valley of collective fragmentation potential and the multi-humped peaks of preformation probability P0 profile are analyzed by considering compact as well as elongated configurations of quadrupole (β2) deformed fragments. The competitive emergence of different symmetric [symmetric superlong (SL), symmetric supershort (SS)] and asymmetric [standard 1 (S1), standard 2 (S2), standard 3 (S3)] fission modes have been observed for the case of elongated configuration. The division of mass and charge in nuclear fission of 254Fm* depicts the importance of spherical and deformed magic shell closures. The most energetic light (AL and heavy (AH) decay fragments of aforementioned fission modes are identified. Moreover, the DCM-calculated fission cross-sections (σ fission) show reasonable agreement with the experimental measurements [24].

Systematic study of probable target-projectile combinations for the synthesis of Z = 120 isotopes using the Skyrme energy density formalism

The synthesis of superheavy elements is an interesting field of research for both theoretical as well as experimental physicists. Till now superheavy element from Z=104 to 118 has been synthesized in various laboratories using cold and hot fusion reactions. Recent predictions of various theoretical models state that Z=120 and N=184 seems most probable doubly magic pair in the island of stability. Hence, we aim to the predict most probable target-projectile combinations of 300,302,304120 superheavy nuclei, so that relevant inputs may be imparted for future synthesis of superheavy nuclei. The target-projectile combinations are taken in reference to the minima's of the fragmentation potential calculated using the Quantum Mechanical Fragmentation Theory (QMFT). In addition, the target-projectile combinations from literature are also considered for which attempts were made for the synthesis of Z=120. The barrier height (VB) of the considered target-projectile combinations are calculated using the spherical and deformed choices of decay fragments. The percentage change in the barrier height ΔVB is explored for the hot and cold fusion approaches. The nuclear interaction potential is obtained within the Skyrme energy density formalism (SEDF) using the GSkI force parameters. For the feasible target-projectile (t-p) combinations, the capture cross-sections of these three isotopes 300,302,304120 are calculated using ℓ-summed Wong model and their comparative analysis is worked out. The probability of formation of compound nucleus (PCN) is determined using the energy dependent function. Among the thirty-six considered target-projectile combinations, the Ti-based reactions with Cf targets and also Cr-based reactions with Cm targets are identified as most suitable combinations for the synthesis of the superheavy element with Z=120. For 300120 isotope are 48Ti+252Cf, 50Ti+250Cf, 50Cr+250Cm, 52Cr+248Cm; whereas 50Ti+252Cf, 54Cr+248Cm, and 54Cr+250Cm form most probable target-projectile pair respectively, for 302120 and 304120 superheavy nuclei.

Systematic Analysis for Neck-Length and Q-Values on Cluster Decay from Ba Isotopes

The present study provides a detailed investigation of the neck-configuration and Q-values on the cluster decay of proton-rich even-even 124-128Ba isotopes using the relativistic mean-field (RMF) formalism with the NL3* parameter set. The densities of the interacting nuclei from the RMF approach are folded with the R3Y and M3Y interactions to obtain the nuclear potential via the double-folding technique. The preformed cluster model (PCM) based on the quantum mechanical fragmentation theory is employed for the calculation of the decay half-lives. The preformation probability P0 and the penetration probabilities are estimated by the phenomenological scaling factor of Blendowske & Walliser and the WKB approximation respectively. The present investigation reveals that the M3Y and R3Y are associated with different barrier characteristics which are significantly modified with a little variation in the neck-length parameter ΔR. From the Q-value analysis, we have demonstrated that α-decay may not be a favourable decay mode for proton-rich barium isotopes with A > 122.

Ternary fission analysis of Fm242,258 nuclei using equatorial and collinear cluster tripartition configurations

The quantum mechanical fragmentation theory--based three cluster model is employed to investigate the ground-state ternary fission of two Fm isotopes nuclei having atomic mass ${A}_{P}=242$ and 258. The mass asymmetry coordinate and the relative separation among the decaying fragments play a crucial role for the estimation of the fragmentation structure and related barrier penetration process. First, the choice of third fragment (${A}_{3}$) is fixed by minimizing the probable ${A}_{3}$ fragments having different proton neutron configurations. Further, the fission fragment combinations (${A}_{1}+{A}_{2}+{A}_{3}$) are identified for the fixed third fragments by selecting the channel of lower ternary fragmentation potential and higher relative fission yield. Two type of tripartition of radioactive nuclei are considered such as equatorial cluster tripartition (ECT) and collinear cluster tripartition (CCT). A comparative analysis of ternary fragmentation potential and relative fission yield within ECT and CCT geometrical arrangement is carried out for different choices of third fragment, i.e., ${A}_{3}=1$ to ${A}_{P}$/3. The choice of most probable fragments suggest that the proton and neutron magic shell closures play essential role in the ternary mass division. Finally, a relative analysis of binary and ternary fragmentation is worked out for better insight of dynamics involved.

Investigation of octupole deformed fragments decaying from even-even isotopes of Th*222–230

Background: In earlier studies, spherical and quadrupole deformed nuclei with closed shells were found to be the most probable fission fragments in the decay of heavy-mass compound nuclei at low excitation energies. Recently, the disintegration of heavy-mass actinides gave evidence of pear-shaped fission fragments, in the mass-asymmetric region, due to extra stability provided by the shell-stabilized octupole deformed $^{144}\mathrm{Ba}$ $(Z=56)$ nucleus.Purpose: In our theoretical work, we have done an exercise to analyze the possibility of octupole deformed fragments in the decay of light- and heavy-mass isotopes of thorium, i.e., $^{222,224,226,228,230}\mathrm{Th}^{*}$.Method: To carry forward the above idea, the mass and charge dispersions of chosen Th isotopes have been analyzed by including deformations (up to ${\ensuremath{\beta}}_{3}$) and related cold optimum orientations within the dynamical cluster-decay model (DCM), which is based on the collective clusterization approach of quantum mechanical fragmentation theory. The above analysis is worked out at low excitation energy, which corresponds to the cold synthesis criteria.Results: In the decay of considered Th isotopes, the minima of fragmentation potential and peaks of preformation probability appear in two regions, near symmetric and asymmetric, respectively due to the presence of quadrupole (${\ensuremath{\beta}}_{2}$) and octupole deformations (${\ensuremath{\beta}}_{3}$) of decay fragments. However, the emission of ${\ensuremath{\beta}}_{3}$-deformed fission fragments is prominent in the heavier isotopes of Th, i.e., $^{226,228,230}\mathrm{Th}^{*}$. The above result is in agreement with the experimentally obtained mass and charge distributions.Conclusions: The disintegration of thorium isotopes into octupole deformed fragments in the asymmetric region signifies their relative stability, which is enhanced for $^{144}\mathrm{Ba}$ ($Z=56$) or in its vicinity.

Binary and Ternary Fragmentation Analysis of 252Cf Nucleus using Different Nuclear Radii

Pioneering study reveals that a radioactive nucleus may split into two or three fragments and the phenomena are known as binary fission and ternary fission respectively. In order to understand the nuclear stability and related structure aspects, it is of huge interest to explore the fragmentation behavior of a radioactive nucleus in binary and ternary decay modes. In view of this, Binary and ternary fission analysis of 252Cf nucleus is carried out using quantum mechanical fragmentation theory (QMFT). The nuclear potential and Coulomb potential are estimated using different versions of radius vector. The fragmentation structure is found to be independent to the choice of fragment radius for binary as wellas ternary decay paths. The deformation effect is included up to quadrupole (β2) with optimum cold orientations and their influence is explored within binary splitting mode. Moreover, the most probable fission channels explore the role of magic shell effects in binary and ternary fission modes.

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 the cold valley paths for the synthesis of isotopes of Ubh in optimum orientations

Cold valley paths have been investigated for the synthesis of isotopes of superheavy element Unbihexium using quantum mechanical fragmentation theory, which suggests the fusion of fission fragments belonging to the cold valleys in the potential energy surfaces with at least one spherical closed shell nucleus as the reaction partner for the nuclear synthesis. For the suitability of the cold valley fission fragments for the synthesis of isotopes of Ubh, first the fragmentation potentials, preformation probabilities and fission barriers of the fission fragments of 314Ubh and 326Ubh compound systems in their ground states have been compared by keeping the fragments either in hot or cold optimum orientations. The comparison suggests 138Ba + 176Yb and 132Sn + 194Os reactions in hot optimum orientations for the synthesis of isotopes of Ubh due to their highest values of preformation probabilities, lowest values of the fragmentation potentials and relatively good values of the fission barriers. Also, the reactions 68Ni + 246Cf and 70Ni + 256Cf have been considered for the comparison with 138Ba + 176Yb and 132Sn + 194Os reactions due to their relatively smaller values of the Coulomb potential, higher mass-asymmetry and fission barrier, and shell closures next to 48Ca which has been used in most of the experiments for the synthesis of superheavy elements. Finally, the excitation functions for the neutron evaporation from the compound systems formed in these reactions, the probabilities of the formation and survival of the compound nuclei have been compared to suggest the suitable cold valley paths energies for the synthesis of the isotopes of Ubh.

Analysis of various competing binary and ternary decay processes of the Es253 nucleus

The ground state binary and ternary decays of the $^{253}\mathrm{Es}$ radioactive nucleus are investigated using the quantum mechanical fragmentation theory (QMFT) based cluster decay models. First, the relative fragmentation of $^{253}\mathrm{Es}$ is analyzed within the framework of the preformed cluster model (PCM). The PCM-calculated binary fragmentation structure is explored for two types of nuclear potential, i.e., Yukawa plus exponential and proximity potentials. The structure of the fragmentation potential and the location of potential minima are found to be independent of the choice of nuclear potential. It is observed from binary fragmentation structures that $\ensuremath{\alpha}$ $(^{4}\mathrm{He})$ decay, cluster $(^{46}\mathrm{Ar})$ emission, heavy particle $(^{82}\mathrm{Ge})$ radioactivity, and spontaneous fission fragmentation $(^{125}\mathrm{In})$ are the possible ground state decay modes of the $^{253}\mathrm{Es}$ nucleus. The competitive emergence of these decay channels is explored by studying the preformation probability ${P}_{0}$, penetrability $P$, and half-lives ${T}_{1/2}$. The calculated half-lives of $\ensuremath{\alpha}$ and spontaneous fission match nicely with the experimental measurements. Also, the half-lives are predicted for cluster and heavy particle radioactivity, for which experimental verification would be of further interest. Further, an effort is made to explore the possibility of ternary fission (particle accompanied fission) for the decay of the $^{253}\mathrm{Es}$ nucleus using the three-cluster model (TCM), where $^{4}\mathrm{He}$ is observed to be the third fragment along with two binary fission fragments. A comparison of relative yields of binary and ternary fission confirm that the probability of the binary fission decay mode is larger than that of ternary fission. Moreover, closed shell effects play a significant role in the symmetric and asymmetric fission of binary and ternary fission, respectively.

Decay of Hot and Rotating $${}^{\boldsymbol{88}}$$Mo$${}^{\boldsymbol{*}}$$ at Incident Energies of 300, 450, and 600 MeV

The reaction mechanism for the decay of the hot and rotating compound system $${}^{88}$$ Mo $${}^{*}$$ formed in $${}^{48}\textrm{Ti}+^{40}$$ Ca reaction and the time for the emission of outgoing fragments have been analyzed within the quantum-mechanical fragmentation theory based dynamical cluster-decay model, at three incident energies. The incident energy effects have been analyzed by comparing the decay modes at three incident energies, i.e. we have calculated and compared the (i) mass, charge, and angular momentum distribution of the cross section for light particles and intermediate mass fragments, (ii) angular momentum distribution of the reaction cross section, (iii) probability of compound nucleus and evaporation processes in the reaction, (iv) mass variation of the kinetic energy, velocity, penetration path length and time for the penetration process, and (v) average time for the process of emission of light particles, intermediate mass fragments and fission fragments. The reaction mechanism has been analyzed from the study of the variation of the reaction cross section with angular momentum.

Cluster radioactivity within the collective fragmentation approach using different mass tables and related deformations

The cluster decay of radioactive nuclei with mass $$^{221}\hbox {Fr}{\le }\hbox {A}{\le }^{252}\hbox {Cf}$$ decaying to lead and near-lead daughters are investigated considering four different sets of binding energies given by Moller et al. (At Data Nucl Data Tables 59:185, 1995) (MN1995), Moller et al. (At Data Nucl Data Tables 109:1, 2016) (MS2016) and Wang et al. (Phys Rev C 81:044322, 2010) (NW2010) with corresponding deformation parameters and experimentally measured data in 2017 (EX2017) considering deformations of the MN1995, MS2016 and NW2010 formalisms. The calculations are carried out using the preformed cluster-decay model based on the collective clusterization approach, which is inherited from the quantum mechanical fragmentation theory. With the incorporation of quadrupole deformations along with optimum cold orientations, the fragmentation potential changes for different choices of binding energy data and hence the preformation probability ($${P}_{0}$$) of the clusters get accordingly modified. The calculated half-lives of the cluster decays find reasonable agreement with the experimental data using the MS2016 formalism. Applying MS2016, the prediction of half-lives of some competing clusters (not measured so far) from known parents is also made in the lead and near-lead region, which could possibly provide new edges for cluster-decay measurements. Further, the role of axial deformations ($$\beta _{2}$$–$$\beta _{4}$$) from various formalisms along with cold elongated configurations of decay products is analyzed in view of cluster emission from the radioactive nuclei considered. The fragmentation profile calculated using MN1995, MS2016 and NW2010 gets significantly influenced when $$\beta _{2}$$-deformations are replaced with $$\beta _{2}$$–$$\beta _{4}$$ deformations. Nearly $$32\%$$ of the clusters are not observed in the decay path using theoretical binding energies and deformation parameters of MN1995, which reduces to $$16\%$$ for MS2016 and $$7\%$$ for NW2010.

Angular momentum as a probe for the reaction mechanism: The [formula omitted] decay at three excitation energies

The angular momentum effects on the reaction mechanism in the decay of a hot system, formed in 48Ti + 40Ca → Mo⁎88 reaction at three excitation energies, have been studied using the dynamical cluster-decay model based on the quantum mechanical fragmentation theory. Angular momentum windows have been defined for the compound and non-compound nucleus processes (like deep inelastic collisions etc.) with respect to the angular momentum variation of the fission barriers of the incoming channel. First, the angular momentum distributions of the summed up preformation, penetration probabilities and the cross-sections for light particles, intermediate mass fragments and fission fragments have been calculated by considering the angular momentum up to the critical value. Then, the mass and charge distributions (with isotopic compositions) of the cross-sections have been calculated in accordance with the defined angular momentum windows. The cross-sections for fragments coming both from the compound nucleus decay and from other processes have been calculated and the total reaction cross-section is compared with the one presented in the work of Valdré and co-workers. The ratios of the observed fusion-evaporation and total fusion cross-sections to the total reaction cross-sections of (i) our calculation and (ii) presented in the work of Valdré and co-workers, are compared and found comparable. The change of the reaction mechanism has been analyzed as a function of the angular momentum variation of the cross-sections of the fission fragments. Finally, the effect of the incident energy on the compound nucleus formation and survival probabilities has been studied.

Systematic decay analysis of 202Po∗ compound nucleus using Dynamical Cluster-decay Model

The decay analysis of [Formula: see text]Po[Formula: see text] compound nucleus (CN), formed via [Formula: see text]Ca+[Formula: see text]Gd reaction, with inclusion of additional degrees-of-freedom, i.e., the higher multipole deformations, the octupole ([Formula: see text]) and hexadecupole ([Formula: see text]), the corresponding “compact” orientations ([Formula: see text]), and noncoplanarity degree-of-freedom ([Formula: see text]0), is investigated within the collective clusterization approach. The Quantum Mechanical Fragmentation Theory (QMFT)-based Dynamical Cluster-decay Model (DCM), wherein the point of penetration [Formula: see text], fixed via the in-built neck-length parameter [Formula: see text] in [Formula: see text] (equivalently, the “barrier lowering” [Formula: see text]), is used to best fit the channel cross-section ([Formula: see text]) and predict the quasi-fission (qf)-like nCN cross-section [Formula: see text], if any, and the fusion–fission ([Formula: see text]) cross-sections. We also look for other target-projectile (t-p) combinations for the synthesis of CN [Formula: see text]Po[Formula: see text].

Analysis of 113In(α,n)[formula omitted]Sb reaction at astrophysically interesting center-of-mass energies and synthesis of 117Sb⁎ within the Dynamical Cluster-decay Model

The Quantum Mechanical Fragmentation Theory (QMFT)-based Dynamical Cluster-decay Model (DCM) analysis of compound nucleus (CN) 117Sb⁎, formed in 4He+113In reaction is done at some astrophysically important energies, which is found to decay via 1n-emission to ground state (g.s.) and metastable state (m.s.) of 116Sb. It is for the first time DCM has been applied to analyze decays to metastable states in a “cold fusion” reaction. The DCM cross sections σ1n are calculated at various astrophysically relevant center-of-mass energies (Ec.m.=9.66–13.64 MeV) corresponding to available experimental data for α-induced reaction with the odd-Z, proton-rich (p-) nuclide 113In, measured with the activation method where, in addition to the radioactive alpha-capture (α,γ), some other reaction channels such as (α,n) and (α,p) of the same isotope can be measured at the same time. The only parameter of DCM is the neck-length parameter ΔR, that is optimized to best fit the experimental data for g.s. to g.s. and g.s. to m.s. decay of 117Sb⁎ CN and predict the cross sections for evaporation-residue (ER), intermediate mass fragments (IMFs) and fusion-fission (ff) fragments. For a best fit to the experimentally observed σ1n (ground and metastable states), we find that, ΔR-values vary smoothly with CN excitation energy ECN⁎ and thus is useful for making predictions at energies where experimental data is unavailable. Possible synthesis of this medically important radionuclide 117Sb⁎ is also studied via all the possible “cold” target-projectile (t–p) combinations, identifying 6Li+111Cd as the best possibility.

Fine structure effect among heavy-ion induced fission fragments at near and above barrier energies

The fission decay analysis of 201Bi*, 206Po*, 212Rn*, 216Ra*, 227Pa* and 228U* nuclei produced in 19F-induced reactions at near and above barrier energies is carried out within the framework of dynamical cluster-decay model (DCM) based on quantum mechanical fragmentation theory (QMFT). The interplay between two modes of fission, i.e. symmetric (SF) and asymmetric (aSF), in the fission fragment mass distributions is investigated. For the present set of calculations the SF to aSF peak ratio is less than unity ($ \frac{P_{SF}}{P_{aSF}} < 1$), which in turn suggests the dominance of asymmetric fission for above mentioned compound nuclei. The role of shell corrections and deformations of fragments in the fission dynamics is duly addressed. The calculated fission cross-sections show nice agreement with the experimental data, except for few energies above the Coulomb barrier. This disagreement is associated with the possible presence of non-compound nucleus (nCN) fission as higher energies are more prone to the nCN process. The study of fission fragment mass distributions is further extended to the isotopic analysis of above mentioned pre-actinide and actinide nuclei at common centre-of-mass energy $ E_{c.m.} \approx 80$ MeV near the Coulomb barrier. It is observed that the lighter isotopes exhibit symmetric fission distribution, whereas heavier ones prefer to decay via asymmetric path. A transition between SF and aSF occurs around fissioning nuclei with $ N/Z \approx 1.4$, showing the triple humped mass distribution suggesting comparable contribution of symmetric and asymmetric fission. Finally, the most energetic asymmetric light ($ A_L$) and heavy ($ A_H$) fission fragments are identified for a long isotopic chain of pre-actinide and actinide nuclei. Interestingly, the heavier asymmetric fission fragments are located near a proton number around $ Z=50$ for the pre-actinide region and $ Z=54$ for actinide nuclei.

Study of α-induced reactions forming A = 60 compound systems within dynamical cluster-decay model

The quantum mechanical fragmentation theory (QMFT)-based dynamical cluster-decay model (DCM) has been applied to predict the fusion cross section (σfus) for the compound systems (CS) 60Zn⁎, 60Ni⁎ and 60Fe⁎ formed, respectively, via 4He+56Ni, 4He+56Fe and 4He+56Cr, reactions, by fixing the only parameter (neck length ΔRemp) of the model, empirically with the available experimental data on σfus of 44,48Ti⁎ and 68Ge⁎ formed through 4He induced reactions at different incident energies, i.e., Elab∼ 10, 13, 17 MeV. We have investigated the effect of neutron to proton (N/Z) ratio in the decay of CS under study, i.e., 60Zn⁎, 60Ni⁎ and 60Fe⁎. The contributions of light-particles cross section (σLPs), intermediate mass fragments cross section (σIMFs) and symmetric mass fragments cross section (σSMFs) are taken together to calculate σfus (=σLPs+σIMFs+σSMFs). The small contribution of SMFs is seen in σfus, the contributions of LPs and IMFs yields being much more prominent, for the decay of all CS under study at different incident energies. We see that the preformation probability (P0) and penetrability (P) for SMFs decrease with increase in the value of N/Z ratio, and hence the symmetric breakup drops-out-of-favor for higher N/Z values. In other words, the symmetric mass decay is favored in the case of 60Zn⁎ having N=Z, the LPs, IMFs and SMFs yields increasing with increase in incident energy.