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

Numerous experimental and theoretical observations have concluded that the probability of the three fragment emission(ternary fission)or binary fission increases when one proceeds towards the heavy mass region of nuclear periodic table.Many factors affect fragment emission,such as the shell effect,deformation,orientation,and fissility parameter.Binary and ternary fissions are observed for both ground and excited states of the nuclei.The collinear cluster tripartition(CCT)channel of the^(235)U(n^(th),f)reaction is studied,and we observe that the CCT may be a sequential or simultaneous emission phenomenon.To date,different approaches have been introduced to study the CCT process as a simultaneous or sequential process,but the decay dynamics of these modes have not been not fully explored.Identifying the three fragments of the sequential process and exploring their related dynamics using an excitation energy dependent approach would be of further interest.Hence,in this study,we investigate the sequential decay mechanism of the^(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 conducted by calculating the fragmentation potential and preformation probability for the spherical and deformed choices of the decaying fragments.The most probable fragment combination of stage I are identified with respect to the dips in the fragmentation structure and the corresponding maxima of the preformation probability(P0).The light fragments of the identified decay channels(obtained in step I)agree closely with the experimentally observed fragments.The excitation energy of the decay channel is calculated using an iteration process.The excitation energy is shared using an excitation energy dependent level density parameter.The obtained excitation energy of the identified heavy fragments is further used to analyze the fragmentation,and the subsequent binary fragments of the sequential process are obtained.The three identified fragments of the sequential process agree with experimental observations and are found near 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.

Study of various ground state decay mechanisms of Actinide nuclei

The special property of the actinide mass region is that nuclei belonging to this group are radioactive and undergo different ground state processes,such as alpha decay,cluster radioactivity(CR),heavy particle radioactivity(HPR),and spontaneous fission(SF).In this study,the probable radioactive decay modes of the heavy mass region(Z=89−102)are studied within the framework of the preformed cluster model(PCM).In the PCM,the radioactive decay modes are explored in terms of the preformation probability(P0)and penetration probability(P)at the turning point Ra,where the penetration of fragments is initiated[Ra=RT(touching state)+ΔR(neck length parameter)].First,the alpha decay half-lives are calculated for light and heavy nuclei,and Ra points are obtained by optimizing the neck length parameter.These Ra points are further employed to fix the Q-value dependent turning point(Ra(Q)).Then,using the(Ra(Q))relation,the decay half-lives are computed,and the calculated results are compared with the available theoretical and experimental data.The isotopical trend of P0 and P is studied with respect to the mass number of the parent and daughter nucleus,respectively.The CR and HPR channels are also explored,and a comparison of calculated data is conducted with the available literature.Comparative analysis of the fragmentation potential and preformation probability is carried out for alpha decay and SF.The mass distribution of the nuclei is studied as a function of fragment mass(A2)by considering the spherical and hot-compact deformation of the decaying fragments.Finally,the most probable fission fragments are identified using the fragmentation structure,and the corresponding fission fragment total kinetic energy of the identified fragments is calculated and compared with available data,wherever applicable.

Decay Analysis of Ge Isotopes Formed in Reactions Induced by Tightly and Loosely Bound Projectiles

The dynamical cluster-decay model (DCM) is employed to investigate the decay of ^(6870)Ge~* compound nuclei formed respectively via tightly (~4He) and loosely (~6He) bound projectiles, using ^(64)Zn target. The study is carried out over a wide energy range (E_(c.m.)～5 MeV to 16 MeV) by including the quadrupole deformations (β_(2i)) and optimum orientations (θ_i^(opt)) of the decaying fragments. The fusion cross-sections, obtained by adding various evaporation channels show nice agreement with the experimental data for ~4He+^(64)Zn reaction. The contribution from competing compound inelastic scattering channel is also analyzed particularly for ^(68)Ge~* nucleus at above barrier energies. On the other hand,the decrement in the fusion cross-sections of ^(70)Ge~* nuclear system is addressed by presuming that ^(65)Zn ER is formed via two different modes:(i) the αn evaporation of ^(70Ge)~* nucleus, and(ii) 1n-evaporation of ^(66)Zn~*nuclear system,formed via breakup and 2n-transfer channels due to halo structure of the ~6He projectile. Besides this, the suppression in2 np evaporation cross-sections suggests the contribution of another breakup and transfer process of ~6He i.e. ~4He+ ^(64)Zn.The contribution of breakup+transfer channels for ~6He+^(64)Zn reaction is duly addressed by applying relevant energy corrections due to the breakup of "~6He" projectile into 2n and ~4He. In addition to this, the barrier lowering, angular momentum and energy dependence effects are also explored in view of the dynamics of chosen reactions.

Study of Cold Fusion Reactions Using Collective Clusterization Approach

Within the framework of the dynamical cluster decay model （DCM）, the in evaporation cross-sections （σ1n） of cold fusion reactions （Pb and Bi targets） are calculated for ZCN = 104-113 superheavy nuclei. The calculations are carried out in the fixed range of excitation energy ECN = 15 ± 1 MeV, so that the comparative analysis of reaction dynamics can be worked out. First of all, the fission barriers （Bf ） and neutron separation energies （S1n） are estimated to account the decreasing cross-sections of cold fusion reactions. In addition to this, the importance of hot optimum orientations of β24-deformed nuclei over cold one is explored at fixed angular momentum and neck-length parameters. The hot optimum orientations support all the target-projectile （t,p） combinations, which are explored experimentally in the cold fusion reactions. Some new target-projectile combinations are also predicted for future exploration. Further, the In cross-sections are addressed for ZCN = 104-113 superheavy nuclei at comparable excitation energies which show the decent agrement with experimental data upto ZCN = 109 nuclei. Finally, to understand the dynamics of higher-Z superheavy nuclei, the cross-sections are also calculated at maximum available energies around the Coulomb barrier and the effect of non-sticking moment of inertia （INS） is also investigated at these energies.

Fusion of spherical-octupole pairs of colliding nuclei for compact and elongated configurations

The deformation and associated optimum/uniquely fixed orientations play an important role in the syn-thesis of compound nuclei via cold and hot fusion reactions,respectively,at the lowest and highest barrier energies.The choice of optimum orientation(0_(op))for the'cold or elongated'and hot or cormpact'fusion configurations of quadrupole(β_(2))deformed nuclei depends only on the+/-signs ofβ_(2)-deformation[J.Phys.G:Nucl.Part.Phys.31,631-644(2005)].In our recent study[Phys.Rev.C 101,051601(R)2020],we proposed a new sct of Oopt(iferent from the values reported for quadrupole deformed nuclei)after the inclusion of octupole deformation(up to B3)ef-fects.Using the respective 0op1 of B3-deformed nuclei for cold and hot optimum orientations,we analyzed the im-pact of the soft-and rigid-pear shapes of octupole deformed nuclei on the fusion barrier characterstics(barrier height Vg and barrier position RB).This analysis is applied to approximately 200 spherical-plus B3 deformed nucle-ar partners,that is,^(16)O,^(18)Cat octupole deformed nuclei.Compared with the compact configuration,the elongated fu-sion configuration has a relatively larger impact on the fusion barrier and cross sections ow ing to the inclusion of de-formations up to B3.Its agreement with available experimental data for the^(16)O+^(150)Sm reaction(β_(22)-0.205,β_(32)=0.055)also improves when the optimum orientation degree of freedom is fixed in view of octupole deformations.This reinforces the fact that nuclear structure effects play an important role in the nuclear fusion process.Thus,octu-pole deformed nuclei can be used for the synthesis of heavy and superheavy nuclei.

Case Control Study of Post-endoscopic Variceal Ligation Bleeding Ulcers in Severe Liver Disease: Outcomes and Management

Background and Aims:The management of post-endoscopic variceal ligation(EVL)bleeding ulcers(PEBUs)is currently based on local expertise and patients liver disease status.The present retrospective study investigated associations between the endoscopic morphology of PEBUs and patient outcomes.Methods:Patients underwent EVL(primary or secondary),from January 2015 to January 2018,in two tertiary care hospitals in India(ILBS New Delhi and Dharamshila Narayana New Delhi).Mortality rates were determined at post-EVL day five and week six.PEBUs were typified based on Jamwal&Sarin classification system as follows:A,ulcer with active spurting;B,ulcer with ooze;C,ulcer base with visible vessel or clot;and D,clean or pigmented base.Results:Of 3854 EVL procedures,141(3.6%)patients developed PEBU,and 46/141(32.6%)suffered mortality.Among the former,the PEBU types A,B,C,and D accounted for 17.7,26.2,36.3,and 19.8%,respectively.Of those who died,39.1,30.4,21.7,and 8.8%had PEBU types A,B,C,and D.Treatments included transjugular intrahepatic portosystemic shunts(TIPS),esophageal self-expandable metal stent(SEMS),glue and sclerosant injection,Sengstaken-Blakemore tube placement and liver transplant.On univariate analysis,no correlation with hepatic venous pressure gradient,TIPS placement,size of varices,or number of bands was found.The Model for EndStage Liver Disease(MELD)-sodium score correlated positively with outcome.After adjusting for MELD-sodium score,mortality was best predicted by type-A ulcer(p=0.024;OR 8.95,CI 1.34-59.72).Conclusions:PEBU occurred in 3.6%of a large EVL cohort.Stratifying patients based on PEBU type can help predict outcomes,independent of the MELD-sodium score.Classifying PEBUs by endoscopic morphology may inform treatment strategies,and warrants further validation.