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The forward recoil range distributions and angular distributions of several evaporation residues produced via complete and incomplete fusion (ICF) dynamics in $^{16}\mathrm{O}+^{148}\mathrm{Nd}$ system at energy $\ensuremath{\approx}6$ MeV/nucleon were measured. The measured forward recoil range distributions of various reaction products show the presence of incomplete fusion components apart from complete fusion. Full and partial linear momentum transfer components of reaction products were found in the interaction of $^{16}\mathrm{O}$ with $^{148}\mathrm{Nd}$. These results were also confirmed by the measurements of angular distributions of evaporation residues. The measured angular distributions of the evaporation residues populated through complete and incomplete fusion channels were found to be distinctly different. The evaporation residues populated via complete fusion channels were trapped in the narrow angular zone as compared to incomplete fusion channels. A systematic study of the dependence of incomplete fusion dynamics on well-known entrance channel parameters shows that the incomplete fusion fraction grows exponentially with mass asymmetry $({\ensuremath{\mu}}_{EC}^{AS})$, Coulomb factor $({Z}_{P}{Z}_{T})$ and $\ensuremath{\alpha}\ensuremath{-}Q$ value of the projectile. The present observations suggest an exponential rise of ICF fraction with entrance channel parameters in contrast with the linear pattern reported in some earlier measurements. Further, the correlation of incomplete fusion fraction with the structure of target (T) was investigated employing four different parameters viz. deformation parameter $({\ensuremath{\beta}}_{2}^{T})$, interaction radius $({R}^{T})$, deformation length $({\ensuremath{\beta}}_{2}^{T}{R}^{T})$ and excess of neutrons ${(N\ensuremath{-}Z)}^{T}$ in the target. In the present study, the ICF fraction was found to rise exponentially with these parameters, independently for different projectiles. The three parameters ${\ensuremath{\beta}}_{2}^{T}, {\ensuremath{\beta}}_{2}^{T}{R}^{T}$, and ${(N\ensuremath{-}Z)}^{T}$ were found more sensitive and effective to investigate the entire picture about the influence of projectile and target deformation along with their relative orientations on incomplete fusion dynamics at low projectile energy. Moreover, the interaction radius of target $({R}^{T})$ is suitable to explain the characteristics of ICF dynamics in the spherical-spherical collisions. These present results show that incomplete fusion dynamics is strongly affected by the structure of projectile along with the target.

A study of low-energy incomplete fusion was done by the measurements of excitation functions of evaporation residues produced in the $^{16}\mathrm{O}+^{148}\mathrm{Nd}$ system at energies $\ensuremath{\approx}4--7$ MeV/nucleon. The stacked foil activation technique using offline $\ensuremath{\gamma}$-ray spectrometry was employed. Significant enhancements were found in the measured cross sections from the theoretical predictions of pace-4 for the evaporation residues populated through $\ensuremath{\alpha}$-emission channels. This enhancement is attributed to incomplete fusion (ICF) of $^{16}\mathrm{O}$ with $^{148}\mathrm{Nd}$. The comparison of present work with literature data shows that the ICF probability increases exponentially with existing entrance channel parameters. The dependence of ICF dynamics on target deformation was investigated using deformation parameter (${\ensuremath{\beta}}_{2}^{T}$), deformation length (${\ensuremath{\beta}}_{2}^{T}{R}^{T}$) and neutron excess ${(N\ensuremath{-}Z)}^{T}$ of the target. The present analysis indicates that the ICF fraction rises exponentially with ${\ensuremath{\beta}}_{2}^{T}$, ${\ensuremath{\beta}}_{2}^{T}{R}^{T}$, and ${(N\ensuremath{-}Z)}^{T}$. These results show that the ICF fraction follows a systematic exponential pattern rather than a simple linear growth with various entrance channel parameters reported in the literature. However, this study also suggests that the ICF dynamics is strongly influenced by the structure of projectile along with that of the target. Further, the role of deformation parameters on incomplete-fusion dynamics was also investigated through the method of universal fusion function. Analysis of the present data indicates that the experimental fusion functions are suppressed with different factors depending on deformation of the target nuclei. These suppressions are removed by including incomplete-fusion cross sections in the fusion function calculations. The average value of experimental fusion functions deviates from the universal fusion function for deformed targets. However, the average value of the total fusion function for deformed targets shifts towards the average value of the universal fusion function. The present study shows that the effect of target deformation plays an important role in affecting the ICF dynamics, along with various entrance channel parameters for different systems.

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.

An attempt has been made to provide crucial information about the dependence of incomplete-fusion dynamics on various entrance channel parameters below 8 MeV/nucleon energy. The forward recoil range distributions of several evaporation residues produced in the $^{13}\mathrm{C}+^{175}\mathrm{Lu}$ system have been measured at $\ensuremath{\approx}88$-MeV energy and examined in the framework of the code SRIM. Owing to the fractional linear momentum transfer from the projectile to the target nucleus, incomplete-fusion (ICF) products are observed to be trapped at lower cumulative thickness than that of complete fusion products. In order to study the incomplete-fusion behavior with various entrance channel parameters, the incomplete-fusion fraction (${F}_{\mathrm{ICF}}$) has also been deduced and compared with those obtained for the systems available in the literature. The reinvestigation of the Coulomb factor $({Z}_{P}{Z}_{T})$ dependence of incomplete fusion indicates that it is somehow projectile structure dependent. No systematic trend is observed with the target deformation parameter $({\ensuremath{\beta}}_{2})$ dependent study of ICF. A systematic linear growth in the incomplete-fusion probability function (${F}_{\mathrm{ICF}}$) is observed with increasing the parameters ${Z}_{P}{Z}_{T}{\ensuremath{\beta}}_{2}$ and ${Z}_{P}{Z}_{T}/(1\ensuremath{-}{\ensuremath{\beta}}_{2})$, but separately for $\ensuremath{\alpha}$- and non-$\ensuremath{\alpha}$-cluster structured projectiles with different targets. The present findings explore the role of Coulomb interaction on ICF dynamics more effectively. Moreover, the projectile $\ensuremath{\alpha}\ensuremath{-}Q$ value is found to be a suitable parameter which explains effectively the observed trend in the study of ICF with the above-mentioned parameters. The incomplete-fusion existence below critical angular momentum (${\ensuremath{\ell}}_{\mathrm{crit}}$), i.e., $\ensuremath{\ell}\phantom{\rule{0.16em}{0ex}}\ensuremath{\le}\phantom{\rule{0.16em}{0ex}}{\ensuremath{\ell}}_{\mathrm{crit}}$, is also observed for the present $^{13}\mathrm{C}+^{175}\mathrm{Lu}$ system.

Excitation functions for the 11 evaporation residues populated through complete and/or incomplete fusion in O16+Sn124 system at low projectile energies ≈3−7MeV/nucleon have been measured. Recoil catcher activation technique followed by offline γ-ray spectrometry has been employed. Some of the evaporation residues are found to have contributions from precursor decays. The precursor contributions have been separated out from the measured cumulative cross-sections of evaporation residues. Independent cross-sections are compared with statistical model code PACE-4 predictions. The evaporation residues produced through xn and pxn channels are found to be well reproduced with the PACE-4 predictions after subtraction of precursor decay contributions. A substantial enhancement in the measured excitation functions over their theoretical predictions for the evaporation residues produced in α-emitting channels has been observed, which is attributed to the presence of incomplete fusion of projectile with target at these low energies. The present study shows that the incomplete fusion and the break-up probability of the incident O16 into α clusters (i.e., break-up of O16 into C12+α and/or Be8+Be8) increases with projectile energy. The present data suggests that the deformation of target is highlighting the important role to affect the ICF reactions independently with different projectiles. The comparison of the present study with literature data also shows that the ICF probability depends on various entrance channel parameters, namely, projectile energy, entrance channel mass-asymmetry, α-Q value, Coulomb factor (ZPZT), deformation parameter (β2), and their combinations. Moreover, the combined parameters ZPZT·β2 and μECAS·β2 are not found suitable to explain whole ICF characteristics, particularly for spherical and slightly deformed targets. On the other hand, the combined parameter ZPZT·μECAS has been found to explain more precisely the ICF dynamics as compared to other single and combined entrance channel parameters.

Spin distributions of nine evaporation residues $^{164}\mathrm{Yb}(xn)$, $^{163}\mathrm{Tm}(pxn)$, $^{168,167}\mathrm{Er}(2pxn)$, $^{163\ensuremath{-}161}\mathrm{Ho}(\ensuremath{\alpha}pxn)$, $^{164}\mathrm{Dy}\phantom{\rule{0.16em}{0ex}}(\ensuremath{\alpha}2pxn)$, and $^{160}\mathrm{Dy}(2\ensuremath{\alpha}xn)$ produced through complete- and incomplete-fusion reactions have been measured in the system $^{16}\mathrm{O}+^{154}\mathrm{Sm}$ at projectile energy $=6.1\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}/\mathrm{nucleon}$ using the in-beam charged-particle ($Z=1,2$)--\ensuremath{\gamma}-ray coincidence technique. The results indicate the occurrence of incomplete fusion involving the breakup of $^{16}\mathrm{O}$ into $^{4}\mathrm{He}+^{12}\mathrm{C}$ and/or $^{8}\mathrm{Be}+^{8}\mathrm{Be}$ followed by fusion of one of the fragments with target nucleus $^{154}\mathrm{Sm}$. The pattern of measured spin distributions of the evaporation residues produced through complete and incomplete fusion are found to be entirely different from each other. It has been observed from these present results that the mean input angular momentum for the evaporation residues produced through complete fusion is relatively lower than that of evaporation residues produced through incomplete-fusion reactions. The pattern of feeding intensity of evaporation residues populated through complete- and incomplete-fusion reactions has also been studied. The evaporation residues populated through complete-fusion channels are strongly fed over a broad spin range and widely populated, while evaporation residues populated through incomplete-fusion reactions are found to have narrow range feeding only for high spin states. Comparison of present results with earlier data suggests that the value of mean input angular momentum is relatively higher for a deformed target and more mass asymmetric system than that of a spherical target and less mass asymmetric system by using the same projectile and the same energy. Thus, present results indicate that the incomplete-fusion reactions not only depend on the mass asymmetry of the system, but also depend on the deformation of the target.

Incomplete fusion of {sup 20}Ne with {sup 59}Co has been investigated at 3-7 MeV/nucleon using the measurement and analysis of excitation functions. The recoil-catcher technique followed by offline gamma-ray spectroscopy has been employed. Evaporation residues are found to have contributions from precursor decays, which have been separated out from the measured cumulative cross sections of evaporation residues. Measured independent cross sections are compared with PACE-2 predictions. The PACE-2 calculations are carried out for evaporation residues formed in complete fusion (CF), and the parameters are optimized so as to reproduce the cross section of evaporation residues produced exclusively in CF, e.g., xn and pxn products. With these parameters, the predicted CF cross sections for alpha emission products are calculated. Any substantial enhancement in the experimental cross section over the PACE-2 prediction is taken as a signature of incomplete fusion (ICF). The analysis indicates the occurrence of incomplete fusion involving the breakup of {sup 20}Ne into {sup 16}O + {sup 4}He and/or {sup 12}C + {sup 8}Be(2{alpha}) followed by fusion of one of the fragments with the target nucleus {sup 59}Co. These data also suggest that the probability of incomplete fusion increases with the projectile energy. Moreover, the ICF probability is foundmore » to increase with entrance-channel mass-asymmetry of the projectile-target systems.« less

Spin distributions for various evaporation residues populated via complete and incomplete fusion of $^{16}\mathrm{O}$ with $^{124}\mathrm{Sn}$ at $6.3$ MeV/nucleon have been measured, using charged particles ($Z=1,2$)-$\ensuremath{\gamma}$ coincidence technique. Experimentally measured spin distributions of the residues produced as incomplete fusion products associated with ``fast'' $\ensuremath{\alpha}$- and $2\ensuremath{\alpha}$-emission channels observed in the ``forward cone'' are found to be distinctly different from those of the residues produced as complete fusion products. Moreover, ``fast'' $\ensuremath{\alpha}$-particles that arise from larger angular momentum in the entrance channel are populated at relatively higher driving input angular momentum than those produced through complete fusion. The incomplete fusion residues are populated in a limited, higher-angular-momentum range, in contrast to the complete fusion products, which are populated over a broad spin range.

Keeping in view the study of complete and incomplete fusion of heavy ions with a target, the forward recoil range distributions of several evaporation residues produced at 164 MeV {sup 20}Ne-ion beam energy have been measured for the system {sup 20}Ne+{sup 165}Ho. The recoil catcher activation technique followed by off-line gamma spectroscopy has been employed. Measured forward recoil range distributions of these evaporation residues show evidence of several incomplete fusion channels in addition to complete fusion. The entire and partial linear momentum transfers inferred from these recoil range distributions were used to identify the evaporation residues formed by complete and incomplete fusion mechanisms. The results indicate the occurrence of incomplete fusion involving the breakup of {sup 20}Ne into {sup 4}He+{sup 16}O and/or {sup 8}Be+{sup 12}C followed by fusion of one of the fragments with target nucleus {sup 165}Ho. Complete and incomplete fusion reaction channels have been identified in the production of various evaporation residues and an attempt has been made to separate out relative contributions of complete and incomplete fusion components from the analysis of the measured recoil range distribution data. The total contribution of complete and incomplete fusion channels has also been estimated.