Projectile Breakup Research Articles

Investigation of the Projectile Breakup Effects on Elastic Scattering and Fusion for 9Be + 209Bi System at Around Barrier Energies

Investigation of the Projectile Breakup Effects on Elastic Scattering and Fusion for 9Be + 209Bi System at Around Barrier Energies

Interplay of breakup and fusion in near-barrier collisions of weakly-bound nuclides

Light, weakly-bound nuclides such as 6,7Li and 9Be exhibit a diverse range of near-barrier reaction phenomena. Complete fusion is found to be suppressed by up to 35% with respect to barrier-passing model calculations. Their weak binding leads to significant breakup through excitation of the continuum, but also through production of weakly-bound or unbound neighbouring nuclides via nucleon transfer. Such systems also exhibit large yields of incomplete fusion, which is correlated empirically with cluster breakup thresholds for these stable nuclides. Disentangling these reaction phenomena and their complex interplay is one of the most interesting challenges in near-barrier reaction dynamics. Here we briefly review our recent progress in understanding the interplay between breakup and fusion. These results strongly suggest that the dominant mechanism leading to incomplete fusion and the suppression of complete fusion is direct capture of the projectile cluster constituents by the target nucleus, rather than requiring projectile breakup prior to fusion.

Analysis of fusion reactions induced by weakly bound nuclei on medium and heavy mass targets

Fusion cross section for reactions induced by weakly bound nuclei 6He, 6,7Li 9,11Be and 10B on targets lying in the mass region 64 ≤ A ≤ 238 have been investigated at around Coulomb barrier energies within the coupled channel formalism. Specifically, the effects of coupling to low-lying excited states of reactants and those arises due to the breakup of projectile have been studied by using Broglia and Winther (BW91), Aage Winther (AW95) and fitted potential (FP) parameterization schemes. Among these the FP scheme is found to be most appropriate in the description of fusion excitation functions of various projectile-target combination. Further, it is observed that in the sub barrier energy region there is an enhancement in the fusion cross section due to coupling to excited states while there occurs fusion suppression at above barrier energies because of the breakup of the projectile.

Systematic study of fusion suppression and its dependency on projectile breakup threshold energy

Measurements of the excitation function (EF) of the observed evaporation residues (ERs) populated in the 20Ne + 93Nb reaction at E lab ≈ 91−145 MeV are carried out to explore the systematic of fusion suppression and its dependency on projectile breakup threshold energy, by employing the offline γ-ray detection method. The EF of the observed ERs populated through complete and/or incomplete fusion processes are analysed in the framework of statistical mode code PACE4. The fusion function, derived from the experimentally measured fusion cross section data, is compared with the universal fusion function (UFF) to estimate the degree of fusion incompleteness. Based on the observed results, an empirical formula is proposed to interrelate the degree of fusion suppression and breakup threshold energy of the incident projectile.

Comprehension of breakup fusion reactions using forward recoil range distribution measurements

To understand the break-up fusion reaction dynamics, the forward recoil range distribution (FRRD) measurements of 12C + 165Ho system at the incident projectile energy of ≈ 88 MeV has been performed. The recoil catcher activation technique followed by the off-line gamma ray spectroscopy was implemented. It is observed that the FRRD measurements of the evaporation residues (ERs) populated via xn and pxn channels have a single Guassian peak at large cumulative thickness. This is attributed to complete momentum transfer from the projectile to the target nucleus. However, in case of the FRRD measurements of the ERs populated via αxn, αpxn and 2αxn emitting channels, in addition to peak corresponding to complete momentum transfer, the Gaussian peaks at lower cumulative thicknesses are also observed. This is accredited to the breakup fusion. Moreover, the effect of projectile breakup on complete fusion cross section is also studied. The suppression in fusion cross section is observed when compared with the universal fusion function, thus indicating the breakup probability of 12C projectile.

Advancing the Ichimura-Austern-Vincent model with continuum-discretized coupled-channels wave functions for realistic descriptions of two-body projectile breakup

Advancing the Ichimura-Austern-Vincent model with continuum-discretized coupled-channels wave functions for realistic descriptions of two-body projectile breakup

Quasielastic scattering of light radioactive and stable projectiles on Be9

Quasielastic scattering angular distributions of radioactive $(^{8}\mathrm{Li},$ $^{7,10}\mathrm{Be}, \mathrm{and} ^{8,12}\mathrm{B})$ and stable $(^{6,7}\mathrm{Li},$ $^{9}\mathrm{Be}, \mathrm{and} ^{11}\mathrm{B})$ projectiles on a $^{9}\mathrm{Be}$ target are presented. The angular distributions have been analyzed by the optical model using Woods-Saxon form factor and S\~ao Paulo potential. Total reaction cross sections have been obtained from the optical model analysis and a comparison between different systems is presented. Coupled channels (CC), coupled reaction channels (CRC), and continuum-discretized coupled channels (CDCC) calculations have been performed to investigate the effect of the cluster configuration in the projectile inelastic excitation, breakup, and stripping reactions on the quasielastic angular distributions.

Systematic study of fusion suppression for tightly bound projectiles at above-barrier energies

The present work aims to explore the effects of projectile breakup on fusion cross section at energies near the Coulomb barrier to well above it. The complete fusion cross section for the strongly bound non-$\ensuremath{\alpha}$-cluster projectile $^{14}\mathrm{N}$ in interaction with a $^{181}\mathrm{Ta}$ target was obtained by summing the experimentally measured channel-by-channel cross section data of evaporated residues. The obtained total fusion cross section was compared with the theoretical code ccfull and the results were found to be consistent with each other. Further, the experimental fusion function data on $^{181}\mathrm{Ta}$ target with $^{14}\mathrm{N}$ projectile were deduced and compared with those obtained for other strongly bound projectiles, viz., $^{12,13}\mathrm{C}$, $^{16}\mathrm{O}$, and $^{19}\mathrm{F}$, in order to get some systematics in fusion reactions. The analysis of experimental fusion functions was performed within the framework of a benchmark curve called the universal fusion function (UFF). A suppression of about 5--25% with respect to UFF was observed for the presently studied systems at energies above the Coulomb barrier, indicating that the suppression is essentially due to the prompt breakup of the projectiles and is a strong function of breakup threshold of projectiles. The magnitude of such suppression was found to be lower for $^{14}\mathrm{N}$ projectile as compared to other strongly bound projectiles. Moreover, an interesting exponential relation between the experimentally deduced suppression factor and the breakup threshold of the projectile was obtained.

Systematic study on the role of various higher-order processes in the breakup of weakly-bound projectiles

Abstract The virtual photon theory (VPT), which is based on first-order Coulomb dissociation restricted to the electric dipole (E1), has been successfully used to explain the breakup data for several cases. Our aim is to study the role of various higher-order processes that are ignored in the VPT, such as the nuclear breakup, interference between nuclear and Coulomb amplitudes, and multistep breakup processes mainly due to strong continuum-continuum couplings in the breakup of two-body projectiles on a heavy target at both intermediate and higher incident energies. For the purpose of numerical calculations, we employed eikonal version of three-body continuum-discretized coupled-channels (CDCC) reaction model. Our results for the breakup of 11Be and 17F on 208Pb target at 100, 250, and 520 MeV/A, show the importance of nuclear breakup contribution, and its significant role in the multistep processes. The multistep effect on Coulomb breakup for core-neutron projectile was found to be negligible, whereas it was important for core-proton projectile. Coulomb-nuclear interference (CNI) effect was also found to be non-negligible. Qantitatively, the multistep effects due to the nuclear breakup was found to depend on the incident energy through the energy dependence of the core-target and nucleon-target nuclear potentials. The nuclear breakup component, the CNI effect, and the multistep breakup processes are all found to be non-negligible; hence, the assumptions adopted in the VPT for the accurate description of breakup cross sections are not valid.

Projectile Break-up Effect on Fusion in 16O + 156Gd Reaction at Energy Range 4.3-6.3 MeV/A

We discuss our present understanding of the incomplete fusion (ICF) reaction dynamics, the excitation function of six evaporation residues (ERs) have been measured in 16O + 156Gd reaction at projectile energy range, E/A ~ 4.3-6.3 MeV/Nucleon. Some of the ERs are produced directly & indirectly (i.e. through pre-cursor), the pre-cursor contributions have been separated out from the measured cumulative cross-section with the help of Cavinato et al.1. After correcting the pre-cursor contribution, the independent yield has been compared with the statistical model code PACE-22, which describes the fusion reaction cross section. In order to optimize the parameter of the code PACE-2 that reproduces the cross section of all the complete fusion (CF) channels like xn and /or pxn-channels. Using the same set of input parameters, cross section of the ERs populated via incomplete fusion (ICF) channels have been measured. The enhancement in the measured cross section of the ERs populated via ICF channels over the PACE-2 prediction have been measured, which indicates the occurrence of the break-up of projectile 16O into (12C+α) and/or (8Be+2α) leading to ICF reaction dynamics.

The São Paulo Potential and the 3He Breakup Reaction at 130 MeV on 93Nb and 197Au

Nuclear reactions induced by weakly bound nuclei often result in the emission of light particles as products of the projectile breakup. The incident particle is expected to fragment before reaching the interior of the target nuclei, a characteristic that tends to favor forward angular emission. Although the first models developed for such reactions were proposed many decades ago by Udagawa and Tamura, Ichimura, Austern, Vincent, and Kasano, and Hussein and McVoy, to this date most of the attention has been dedicated to the breakup of the deuteron and other very weakly bound systems, while more strongly bound projectiles have not been fully explored. Here, we describe the production of protons and deuterons from the breakup of 3He. The breakup of 3He on two heavy targets, 93Nb and 197Au, is analyzed in this study. However, the incoming energy involved is much larger than that of the standard phenomenological optical potentials available in the literature for the 3He entrance channel. We have overcome this difficulty by using the São Paulo potential and adjusting the nuclear diffusivity. The deuteron inclusive spectra were calculated at several angles and compared well with the experimental data. Theoretical proton emission predictions are also given for future reference, since no inclusive measurements were performed for the targets under study. One of our goals is to verify the description of deuteron emission from fast projectiles, for which many partial waves contribute to the scattering process.

Analysis of Fusion Cross Sections in the 9Be Projectile Breakup on Different Target Nuclei

We present a theoretical study of total fusion (TF), complete fusion (CF), and incomplete fusion (ICF) cross sections in the breakup of 9Be (described as n −8Be) projectile on 124Sn, 144Sm and 208Pb target nuclei. We use the continuum discretized coupled-channel formalism together with a sum-rule model, by extending an approach outlined in Mukeru et al. (Nucl. Phys. A 996:121700, 2020) to another weakly bound projectile in different targets. The applicability of the model to incident energies below and around the Coulomb barrier is verified, being confirmed for all three reactions an empirical energy-dependent cutoff angular momentum expression. We show that the TF and ICF cross sections are strongly dependent on the projectile binding energy eb, whereas the CF is weakly affected by that. Despite this weak dependence, the CF contribution to the TF cross section becomes more suppressed by decreasing eb. The dependence of the ICF probability on the breakup threshold is also highlighted.

Projectile breakup effects in the fusion dynamics of 6,7Li +144,152Sm reactions around Coulomb barrier

This work emphasized the role of the projectile breakup channel by studying the complete fusion (CF) and incomplete fusion (ICF) dynamics of [Formula: see text] reactions. The theoretical calculations for the chosen reactions have been done by opting for the coupled channel approach and the energy dependent Woods–Saxon potential (EDWSP) model. The below barrier fusion enhancements of the studied reactions are reasonably addressed by the outcomes of the adopted models, which in turn can be attributed to the couplings of nuclear structure degrees of freedom of the collision partners to their relative motion. In contrast, at above barrier energies, the CF cross-section data of the chosen reactions are found to be suppressed significantly when compared with the predictions made by using the present models. Interestingly, the fusion suppression factors of the given reactions can be minimized considerably with respect to the reported value when it is analyzed within the framework of the EDWSP model. For instance, in case of [Formula: see text] ([Formula: see text] reaction, the magnitude of fusion suppression factor is minimized up to 7% (13%) relative to the reported value whereas for [Formula: see text] ([Formula: see text] reaction, the fusion suppression factor is found to be less by 7% (8%) with reference to the reported value. Such suppression effects can be correlated with the low breakup threshold of alpha breakup channel associated with the loosely bound projectile. The projectiles being weakly bound systems split into two charged fragments and either of the breakup components is absorbed by the target resulting in the reduction of incoming flux going into fusion channel. The flux lost from the CF channel appears in the form of ICF yields. For [Formula: see text], total fusion (TF) cross-sections that are sum of CF and ICF cross-sections are also analyzed in conjunction with the EDWSP model and thus reasonably explained by the model calculations. In order to identify the ICF contribution, the ratio of ICF/TF cross-section data of [Formula: see text] reaction has been examined and thus properly addressed by using the EDWSP model. The presence of ICF component in TF cross-section clearly pointed out the breakup of projectile due to its loosely bound nature prior to the Coulomb barrier. Although ICF data of other systems are not available in the literature, a similar behavior is expected for ICF and TF data for [Formula: see text] and [Formula: see text] reactions.

Dynamical versus statistical production of Intermediate Mass Fragments at Fermi Energies

The emission probability of Intermediate Mass Fragments (IMFs) in non-central reactions has been investigated in collisions of heavy $$^{124}\hbox {Xe}$$ projectiles with the two different medium-mass targets of $$^{64}\hbox {Ni}$$ and $$^{64}\hbox {Zn}$$ at the laboratory energy of 35 A MeV. The two colliding systems differ only for the target atomic number Z and, consequently, for the isospin N/Z ratio. The probability of IMFs emission from the projectile-like fragment has been measured, showing an enhancement of the IMFs emission for the neutron rich $$^{64}\hbox {Ni}$$ target. Most of the observed projectile break-up yield is associated with the production of only one IMF, that is, a quasi-binary splitting of projectile in two fragments in a broad range of charge asymmetry. For the events with one IMF, the relative contributions of the dynamical and statistical emissions have been evaluated. We find an enhancement of dynamical break-up probability for the neutron rich target with respect to the neutron poor one. The analysis suggests influence of the target isospin in inducing the dynamical break-up of projectile-like fragments. The new data have been also compared with previous published results of $$^{112,124}\hbox {Sn}$$ + $$^{58,64}\hbox {Ni}$$ systems, in order to disentangle between isospin effects against system-size effects on the emission probability. The comparisons between previous and new data suggest that the dynamical break-up is determined by the N/Z content of both projectile and target; for the cases here investigated, the influence of the system size on the dynamical emission probability can be excluded.

Effect of projectile breakup in the system 19F + 154Sm

An attempt was made to understand the role of various entrance channel parameters on incomplete fusion dynamics by the measurements of excitation functions of evaporation residues populated via complete and incomplete fusion dynamics in the system 19 F + 154 Sm at projectile energy ≈ 4-6 MeV/A. The stacked foil activation technique followed by offline gamma ray spectrometry was employed in these measurements. The measured excitation functions of various evaporation residues populated have been analyzed within the framework of statistical model code PACE-4. It has been observed that the measured excitation functions of xn and pxn emission channels agree well with the theoretical predictions of PACE-4. On the other hand, the measured excitation functions of α-emission channels have been found significantly enhanced over their theoretical predictions. This enhancement may be attributed to the incomplete fusion of the projectile 19 F as the calculations for incomplete fusion are not included in statistical model calculations. The incomplete fusion fraction has been deduced from the present measurements. Further, a systematic study has also been performed, which shows that the incomplete fusion increases significantly with entrance channel mass asymmetry at low projectile energy, differently for different projectiles.

Systematic study of the break-up fusion process in the C12+Ho165 system and interplay of entrance channel parameters

To understand the low-energy incomplete fusion (ICF) reaction dynamics, the excitation function measurements of $^{12}\mathrm{C}+^{165}\mathrm{Ho}$ system has been performed in the energy region of \ensuremath{\approx} 4--7 MeV/nucleon, by employing the stacked foil activation technique. The cross sections of the measured evaporation residues are compared with the theoretical predictions of statistical model code PACE4, which takes into account only the complete fusion (CF) reaction cross section. It is observed that residues populated via xn and pxn channels are in good agreement with the PACE4 predictions, implying that these residues are populated via CF process. However, in the case of \ensuremath{\alpha}-emission channels a significant enhancement from the PACE4 predictions is observed even after the deduction of precursor contribution, which is accredited to ICF process. The projectile break-up probability is found to increase with increment in the incident projectile energy. Further, the dependence of incomplete fusion dynamics on entrance channel parameters like mass asymmetry, Coulomb effect (${Z}_{\mathrm{P}}{Z}_{\mathrm{T}}$), and projectile ${Q}_{\ensuremath{\alpha}}$ value is systematically studied. The present results reveal that a single entrance channel parameter does not oversee the ICF reaction dynamics but have varying contributions depending upon the projectile-target combination. Moreover, the effect of projectile break-up on complete fusion cross section at energies above the Coulomb barrier is also studied. The suppression in fusion cross section is observed when compared with the universal fusion function.

Thick target neutron yields from 100- and 230-MeV/nucleon helium ions bombarding water, PMMA, and iron

The secondary neutrons produced from 100- and 230-MeV/nucleon 4He ions, respectively, stopping in the thick natFe, PMMA and water targets are measured by the time of flight method combined with the pulse shape discrimination of liquid scintillation detectors. The experimental data show that the secondary neutrons were contributed from breakup of projectiles, emission from overlap regions of projectile nuclei and target nuclei, and evaporation of projectiles and target nuclei.The measured quantities, including the double-differential thick target neutron yields, angular distributions, and total neutron yields per ion, were benchmarked against model calculations with the PHITS, FLUKA, and MCNP Monte Carlo simulation codes. The default models implemented in these codes agree the experimental data well at intermediate-to-large angles in the low-to-intermediate energy range. However, the physics models implemented in the FLUKA and the PHITS codes under-predict secondary neutrons at energies higher than the specific beam energies by more than one order. The energy-integrated simulation yields at 0° differ from the measured values by −75% to 240%. The underestimation of low-energy neutron yields by the models at small angles for 230-MeV/nucleon 4He projectiles on the light targets are as much as five times lower. Our results indicate that improvements are needed in the physics models used to describe 4He-induced nuclear reactions for predictions of neutron production.

Origins of Incomplete Fusion Products and the Suppression of Complete Fusion in Reactions of ^{7}Li.

Above-barrier complete fusion involving nuclides with low binding energy is typically suppressed by 30%. The mechanism that causes this suppression, and produces the associated incomplete fusion products, is controversial. We have developed a new experimental approach to investigate the mechanisms that produce incomplete fusion products, combining singles and coincidence measurements of light fragments and heavy residues in ^{7}Li+^{209}Bi reactions. For polonium isotopes, the dominant incomplete fusion product, only a small fraction can be explained by projectile breakup followed by capture: the dominant mechanism is triton cluster transfer. Suppression of complete fusion is therefore primarily a consequence of clustering in weakly bound nuclei rather than their breakup prior to reaching the fusion barrier. This implies that suppression of complete fusion will occur in reactions of nuclides where strong clustering is present.

Influence of projectile breakup on fusion reactions induced by 9Be at near barrier energies

We have analyzed the fusion excitation functions of various fusion reactions involving 9Be as projectile in the near barrier energy region using proximity potential and quantum diffusion approach. In particular, the role of breakup is investigated in these fusion reactions. For Be9+124Sn, 169Tm, 181Ta, 187Re projectile–target combinations an overall suppression in fusion cross section is observed while for Be9+144Sm, 186W, 208Pb, 209Bi systems overall enhancement is found in near barrier energy region. The agreement between data and predictions is found to be improved significantly when breakup effects are properly accounted for.

Investigation of fusion hindrance in a soft asymmetric system deep below the barrier

A steeper fall of fusion excitation function, compared to the predictions of coupled-channel (CC) models, at energies below the lowest barrier between the reaction partners, is termed as deep sub-barrier fusion hindrance. This phenomenon has been observed in many symmetric and nearly symmetric systems. Different physical origins of the hindrance have been proposed though a complete understanding is yet to be achieved. This work reports the measurement of the fusion (evaporation residue) cross sections for the system 19F+181Ta, from above the barrier down to the energies where fusion hindrance is expected to come into play. CC calculation with standard Woods–Saxon potential gives a fair description of the fusion excitation function down to energies ≃14% below the barrier. This is in contrast with the observation of increasing fusion hindrance in asymmetric reactions induced by increasingly heavier projectiles, viz. 6,7Li, 11B, 12C and 16O. The most likely reason for non-observation of fusion hindrance in the present system is the ‘softness’ of the collision partners. The ‘threshold’ for the onset of fusion hindrance in reactions involving well-deformed nuclei is expected to be at an energy lower than that estimated from the systematics. It is also noted that the asymmetric reactions, which have not shown any signature of fusion hindrance within the measured energy range, are induced by projectiles with low α-particle break-up threshold and have positive Q-values for most light particle pick-up channels. Since CC calculation reproduces the fusion excitation functions for these systems, probable roles of projectile break-up and particle transfer in fusion deep below the barrier are not conclusively proven. Further measurements and inclusion of break-up and transfer channels within the framework of CC formalism would be of interest.