Strength Of Incomplete Fusion Research Articles

Disentangling fractional momentum transfer in the F19+Sm154 system

Forward recoil range distributions of evaporation residues produced in the system $^{19}\mathrm{F}+^{154}\mathrm{Sm}$ were measured at projectile energy $\ensuremath{\approx}107$ MeV using the offline $\ensuremath{\gamma}$-ray activation technique. The entire and fractional linear momentum transfers inferred from these recoil range distributions were used to identify the evaporation residues formed by complete and incomplete fusion mechanisms. The forward recoil range distributions of measured evaporation residues populated through $x\mathrm{n}/\mathrm{p}x\mathrm{n}$ channels were found to be consisting of a single peak only while the evaporation residues populated through $\ensuremath{\alpha}$ emitting channel had contributions from incomplete fusion also. The observed incomplete fusion process in the population of $\ensuremath{\alpha}$ emitting channel residues is explained through the breakup fusion model. The results indicate the occurrence of incomplete fusion involving the breakup of $^{19}\mathrm{F}$ into $^{4}\mathrm{He}+^{15}\mathrm{N}$ and/or $^{8}\mathrm{Be}+^{11}\mathrm{B}$ followed by fusion of one of the fragments with target nucleus $^{154}\mathrm{Sm}$. From these measurements, the relative contributions of complete and incomplete fusion were separated out. The forward recoil range distributions data show that the incomplete fusion contribution in the fusion of fragment $^{15}\mathrm{N}$ is more dominant as compared to the fusion of fragment $^{11}\mathrm{B}$ with $^{154}\mathrm{Sm}$ target due to the smaller value of $\ensuremath{\alpha}$ breakup threshold energy $({E}_{\mathrm{B}.\mathrm{U}.}^{\ensuremath{\alpha}})$. The measured forward recoil range distributions of evaporation residues produced through $\ensuremath{\alpha}$ emitting channels provide experimental signature of strong clustering in $^{19}\mathrm{F}$ projectile as $\ensuremath{\alpha}$ and $^{15}\mathrm{N}$. The incomplete fusion strength function has also been deduced from the measured recoil range distributions and found to be compatible with those deduced from the measured excitation functions for the same system and beam energy.

Role of the entrance channel in the experimental study of incomplete fusion of 13 C with 93 Nb

We report measured cross-section data of the residues produced in the $^{13}\mathrm{C}$-induced reaction on $^{93}\mathrm{Nb}$ within the 63.7--87.1-MeV energy range. The off-line $\ensuremath{\gamma}$-ray spectroscopy method has been used to measure the cross sections of the radionuclides produced in this system. The analysis of present measured cross-section data has been carried out within the light of well-established statistical model code pace4. The excitation function of residues populated via $xn$ and/or $pxn$ channels are found to be in fair agreement with those estimated by the theoretical model code, which confirms the assembly of these residues via complete fusion process. A considerable enhancement in the measured cross-section data has been observed for the residues involving $\ensuremath{\alpha}$-emitting channels as compared to the theoretical predictions. The observed enhancement in the cross sections has been assigned to the incomplete fusion processes. Furthermore, in order to have a better insight into the onset and strength of incomplete fusion, termed as the incomplete fusion fraction has been deduced for the present paper and is compared with $^{16}\mathrm{O}$ and $^{18}\mathrm{O}$ beams on the same target $^{93}\mathrm{Nb}$. This suggests that the incomplete fusion fraction is strongly influenced by the entrance channel, which may be understood in terms of the projectile ${Q}_{\ensuremath{\alpha}}$ value. The comparison of this paper with literature data also shows that the incomplete fusion probability increases with various entrance channel parameters, such as projectile structure, projectile energy, and mass asymmetry of interacting partners.

Effect of projectile structure on break-up fusion for 14N + 175Lu system at intermediate energies

In the present work, fusion in heavy-ion collisions at energies near the Coulomb barrier to ≈ 33% above it has been studied for 14N + 175Lu system. The excitation functions of several reaction channels expected to be populated via complete fusion and/or the incomplete fusion of the projectile have been measured. The experimental excitation functions have been critically compared with the predictions of the statistical model code PACE4. The observed enhancement in the measured cross-sections with respect to the theoretical model code PACE4 predictions of all the reactions having α-particle(s) in the exit channel is reminiscent of the fact that incomplete fusion (ICF) is at work in populating these channels besides the complete fusion process. The relative probability of incomplete fusion in fusion dynamics, obtained in terms of incomplete fusion strength function FICF has also been deduced. The observed behavior of FICF suggests the increasing probability of ICF contributions with projectile energy. A strong and a dictating dependence of FICF on projectile structure in terms of its Qα-value has been observed. The reduction procedures for the elimination of the geometric and the static effects suggest that the observed variation in the fusion data has a purely static origin i.e., a manifestation of different potential barriers and radii. The analysis done within the framework of universal fusion function indicates the fusion suppression of ≈ 5% for the 14N + 175Lu system.

Mass-number dependence of statistical model parameters and its impact on incomplete fusion fraction calculations

Incomplete fusion processes and estimation of strength of incomplete fusion in heavy ion induced nuclear reactions have been explored for several combinations of projectile-target nuclei. Dynamics of these reactions is explained using an optical model. Parameters of the optical model affect the shape and depth of nuclear potential and hence influence the theoretical predictions. For heavy ion induced reactions, the optical model potential parameters are not unique and different sets of these parameters may be used for different ranges of mass number $A$ and incident energy $E$. To explore the effect of optical model potential parameters, a comparative study of available experimental data for excitation functions of four systems, $^{16}\mathrm{O}+^{181}\mathrm{Ta}, ^{12}\mathrm{C}+^{165}\mathrm{Ho}, ^{14}\mathrm{N}+^{163}\mathrm{Dy}$, and $^{16}\mathrm{O}+^{74}\mathrm{Ge}$, with corresponding theoretically predicted excitation functions, made by PACE4 using different sets of optical model potential parameters, has been done. It has been observed that a single set of optical model potential parameters is not adequate for all the systems. The variations in these parameters change the theoretical cross-section predictions for various channels considerably, which in turn, change the correspondingly estimated fraction of incomplete fusion $({F}_{\mathrm{ICF}})$. The effect of deformation of target nuclei on fractional incomplete fusion has also been investigated for the above mentioned systems. ${F}_{\mathrm{ICF}}$ has been plotted as a function of deformation parameter $({\ensuremath{\beta}}_{2})$ of the target nuclei and it is found to increase as the deformation parameter of the corresponding target nuclei increases on either side of the intrinsic spherical symmetry.

Probing the influence of incomplete fusion in the Li6+Y89 reaction up to 7.2 MeV/nucleon energy

The nuclear reaction study with weakly bound heavy nuclei is an enduring open question due to the scarcity of experimental data. In view of this, an experiment has been performed to study the fusion dynamics of weakly bound $^{6}\mathrm{Li}$ projectile in $^{6}\mathrm{Li}+^{89}\mathrm{Y}$ reaction at energies slightly above the Coulomb barrier. The off-beam $\ensuremath{\gamma}$-spectroscopic technique has been used to measure the cross sections of populated residues in $^{6}\mathrm{Li}+^{89}\mathrm{Y}$ reaction, and the data are analyzed using equilibrium and pre-equilibrium models in the framework of the empire3.2.2 code. It has been found that complete fusion (CF) and incomplete fusion (ICF) of $^{6}\mathrm{Li}$ play a substantial role in producing the residues. Subsequently, the ICF cross section, which is a model-dependent quantity, has been extracted. The strength of incomplete fusion has been deduced and compared with the existing data from $^{7}\mathrm{Li}+^{89}\mathrm{Y}$ reaction. The ICF strength is found to be higher for $^{6}\mathrm{Li}+^{89}\mathrm{Y}$ as compared with the $^{7}\mathrm{Li}+^{89}\mathrm{Y}$ system, which possibly indicates the role of the projectile's structure on the ICF occurrence probability. The occurrence of ICF below a critical angular momentum is also anticipated for both $^{6}\mathrm{Li}$ and $^{7}\mathrm{Li}$ interaction with $^{89}\mathrm{Y}$.

Effect of neutron excess in the entrance channel on the O18+Nb93 system: An experimental study relevant to incomplete-fusion dynamics

The incomplete fusion dynamics in the $^{18}\mathrm{O}+^{93}\mathrm{Nb}$ system at energies above the Coulomb barrier has been investigated. The experimentally measured cross sections have been compared with the theoretical predictions of the statistical model code pace4. To examine the effect of entrance channel parameters on the onset and strength of incomplete fusion, relative contributions of complete and incomplete fusion have been deduced from the analysis of measured excitation functions. The contribution of incomplete fusion deduced from the analysis of excitation functions has been studied in terms of various entrance channel parameters, namely, entrance channel mass asymmetry (${\ensuremath{\mu}}_{A}$) of interacting projectile and target combination, Coulomb factor (${Z}_{P}{Z}_{T}$), ground state $\ensuremath{\alpha}\text{\ensuremath{-}}Q$ value of the reaction, and neutron skin thickness of target nuclei. It has been found that the probability of incomplete fusion depends strongly on entrance channel parameters. Further, the incomplete fusion contribution for the $^{18}\mathrm{O}$ projectile with two excess neutrons is noticed to be relatively larger as compared to $^{16}\mathrm{O}$. This may be due to the larger probability of breakup for the $^{18}\mathrm{O}$ projectile resulting in rather weak binding forces as compared to $^{16}\mathrm{O}$. The existence of incomplete fusion below critical angular momentum (${\ensuremath{\ell}}_{\mathrm{crit}}$), i.e., $\ensuremath{\ell}\ensuremath{\leqslant}\phantom{\rule{4pt}{0ex}}{\ensuremath{\ell}}_{\mathrm{crit}}$, has also been observed for the studied system.

Analysis of the dynamics of Li7 -induced fusion with natZr up to 44 MeV

An experimental study on the fusion dynamics of the $^{7}\mathrm{Li}+^{\text{nat}}\mathrm{Zr}$ reaction has been carried out within the 4.0 to 6.3 MeV/nucleon energy range by measuring cross sections of the populated residues with the help of $\ensuremath{\gamma}$-ray spectrometry. The equilibrium and pre-equilibrium reaction models have been used in the framework of empire3.2.2 to analyze the measured residual cross sections to shed light on the reaction mechanism involved in it. It indicates that the complete and incomplete fusion of $^{7}\mathrm{Li}$ contribute to the residual cross sections. Thus, the strength of incomplete fusion has been derived and is compared with other $^{7}\mathrm{Li}$-induced reactions in the similar mass range. Further, coupled channel (CC) calculations have been carried out to understand the effect of couplings in the fusion process. It has been observed that the fusion cross section is suppressed in $^{7}\mathrm{Li}+^{\text{nat}}\mathrm{Zr}$ reaction as compared to CC calculations far above the Coulomb barrier. The isomeric cross-section ratio has also been obtained from the measured cross sections of the isomeric pairs of $^{93,95}\mathrm{Tc}$ that describes the role of angular momentum and relative spins of the ground and isomeric states with the variation of bombarding energy.

Measurement of residual cross sections in the Li7+Y89 reaction up to 5.7 MeV/nucleon and analysis of fusion mechanisms

Different modes of fusion phenomena observed in the isolated experiments are not yet fully understood. To comprehend these fusion mechanisms, more experimental studies are necessary. In view of this, a new measurement of residual cross sections from the $^{7}\mathrm{Li}$-induced reaction on $^{89}\mathrm{Y}$ has been reported in this article within the 2.7--5.7 MeV/nucleon energy range. The $\ensuremath{\gamma}$-ray spectrometry has been used to identify the residues $^{93m}\mathrm{Mo}, ^{92m}\mathrm{Nb}, ^{89}\mathrm{Zr}, ^{91m}\mathrm{Y}$, and $^{90m}\mathrm{Y}$ produced in the reaction. A systematic analysis of the complete and incomplete fusion dynamics has been carried out by comparing the measured excitation functions with the equilibrium and pre-equilibrium reaction models in the framework of empire3.2.2 and alice19. A strong indication of the occurrence of incomplete fusion has been realized within the energy range considered; hence the incomplete fusion strength is discussed in detail. The product yield of $^{93m}\mathrm{Mo}$, which is a candidate radionuclide for radiopharmaceuticals, has been estimated.

Variation of ICF strength function with projectile energy for 12C + 165Ho system at Elab ≤ 7MeV/A

During the last few decades, research in heavy-ion induced nuclear reactions has opened numerous fields, in its theoretical and experimental domains. At energies, from near the Coulomb barrier to well above it, the complete fusion (CF) and incomplete fusion (ICF) reactions compete with each other. The relative contribution of these processes depends on various entrance channel parameters. In order to study the dependence of CF and ICF reaction dynamics on various entrance channel parameters, comparative studies with different parameters of the statistical model codes have been done. In this paper, an attempt has been made to study the dependence of incomplete fusion strength function on incident energy for 12 C + 165 Ho system at energies ≤ 7 MeV/A. The analysis of data has been done within the frame work of statistical model code PACE4, which do not take ICF into account; and thus predicts cross-section values only due to complete fusion process. For the present reaction system, the excitation functions (EFs) of xn/pxn channels, predicted by PACE4 code, well reproduces the experimentally measured values, indicating their production via CF process only. However, for α and 2α-emitting channels, calculated EFs through PACE4 code underpredict the experimentally measured cross-sections by »25-30%, in general. The enhancement of experimental cross-sections for α and 2α-emitting channels as compared to the PACE4 predictions, indicates that the major contribution of their production comes from the ICF of 12 C, if it breaks up into 8 Be and α-fragments, and one of the fragments fuses with the target nucleus. The incomplete fusion strength function (F ICF ), which gives relative importance of ICF processes over CF process has also been deduced and is found to depend sensitively on beam energy.

Insights into the low energy incomplete fusion

In the present work, channel-by-channel excitation functions of different evaporation residues populated via complete and/or incomplete fusion in C12+169Tm system have been measured for an energy range Elab≈53–90MeV, using recoil-catcher activation technique followed by off-line γ-spectroscopy. Experimentally measured excitation functions have been analysed in the framework of statistical model code pace. To probe the effect of entrance-channel parameters on the onset and strength of incomplete fusion, relative contributions of complete and incomplete fusion have been deduced from the analysis of experimentally measured excitation functions. The percentage fraction of incomplete fusion deduced from the analysis of excitation functions has been studied in terms of incident energy, entrance-channel mass-asymmetry, ground state alpha-Q-value, neutron skin thickness of target nuclei, and nuclear potential parameters. It has been found that incomplete fusion start competing with complete fusion even at slightly above barrier energies where complete fusion is assumed to the sole contributor. The probability of incomplete fusion increases with incident energy, entrance channel mass-asymmetry, large negative ground state alpha-Q-value, neutron skin thickness, and nuclear potential parameters for individual projectiles.

Investigation of Incomplete Fusion events: Recent Results

The dynamics of incomplete fusion processes has been extensively investigated and is found to compete with complete fusion at low incident energies (i.e. ≤ 7.0 MeV/A). Recent reports suggest that the probability of incomplete fusion depends on Qα of the projectile, and found to be originated from the high input angular momentum provided into the system due to non-central collisions. Apart from the well documented existence of low energy incomplete fusion, a strong contradiction on previously established mass-asymmetry systematics has been noticed recently. It has been found that the incomplete fusion fraction increases with entrance channel mass-asymmetry for the individual projectiles. Further, a strong dependence of incomplete fusion on the Coulomb effect (ZP ZT ) has been observed and is found to increase linearly with ZP ZT, a significantly important approach to understand the breakup fusion reactions. For better insights into the onset and strength of incomplete fusion in terms of various entrance channel parameters and to understand the role of high angular momenta in the onset of incomplete fusion, a quality data have been obtained in a variety of experiments performed at the Inter-University Accelerator Center (IUAC), New Delhi, India. Some of the recent results are presented in this paper, conclusively demonstrating the effect of entrance channel parameters on the onset and strength of incomplete fusion, and the usefulness of incomplete fusion to populate high-spin states in final reaction products.

Low-energy nuclear reaction of the N14+Tm169 system: Incomplete fusion

Excitation functions of reaction residues produced in the $^{14}\mathrm{N}+^{169}\mathrm{Tm}$ system have been measured to high precision at energies above the fusion barrier, ranging from $1.04{V}_{B}$ to $1.30{V}_{B}$, and analyzed in the framework of the statistical model code pace4. Analysis of $\ensuremath{\alpha}$-emitting channels points toward the onset of incomplete fusion even at slightly above-barrier energies where complete fusion is supposed to be one of the dominant processes. The onset and strength of incomplete fusion have been deduced and studied in terms of various entrance channel parameters. Present results together with the reanalysis of existing data for various projectile-target combinations conclusively suggest strong influence of projectile structure on the onset of incomplete fusion. Also, a strong dependence on the Coulomb effect $({Z}_{P}{Z}_{T})$ has been observed for the present system along with different projectile-target combinations available in the literature. It is concluded that the fraction of incomplete fusion linearly increases with ${Z}_{P}{Z}_{T}$ and is found to be more for larger ${Z}_{P}{Z}_{T}$ values, indicating significantly important linear systematics.

Influence of incomplete fusion on complete fusion at energies above the Coulomb barrier

In the present work, excitation functions of several reaction residues in the system 19F+169Tm, populated via the complete and incomplete fusion processes, have been measured using off-line γ-ray spectroscopy. The analysis of excitation functions has been done within the framework of statistical model code pace4. The excitation functions of residues populated via xn and pxn channels are found to be in good agreement with those estimated by the theoretical model code, which confirms the production of these residues solely via complete fusion process. However, a significant enhancement has been observed in the cross-sections of residues involving α-emitting channels as compared to the theoretical predictions. The observed enhancement in the cross-sections has been attributed to the incomplete fusion processes. In order to have a better insight into the onset and strength of incomplete fusion, the incomplete fusion strength function has been deduced. At present, there is no theoretical model available which can satisfactorily explain the incomplete fusion reaction data at energies ≈4–6 MeV/nucleon. In the present work, the influence of incomplete fusion on complete fusion in the 19F+169Tm system has also been studied. The measured cross-section data may be important for the development of reactor technology as well. It has been found that the incomplete fusion strength function strongly depends on the α-Q value of the projectile, which is found to be in good agreement with the existing literature data. The analysis strongly supports the projectile-dependent mass-asymmetry systematics. In order to study the influence of Coulomb effect () on incomplete fusion, the deduced strength function for the present work is compared with the nearby projectile–target combinations. The incomplete fusion strength function is found to increase linearly with , indicating a strong influence of Coulomb effect in the incomplete fusion reactions.

Effect of projectile on incomplete fusion reactions at low energies

Present work deals with the experimental studies of incomplete fusion reaction dynamics at energies as low as ≈ 4 - 7 MeV/A. Excitation functions populated via complete fusion and/or incomplete fusion processes in 12 C+175 Lu, and 13 C+169 Tm systems have been measured within the framework of PACE4 code. Data of excitation function measurements on comparison with different projectile-target combinations suggest the existence of ICF even at slightly above barrier energies where complete fusion (CF) is supposed to be the sole contributor, and further demonstrates strong projectile structure dependence of ICF. The incomplete fusion strength functions for 12 C+175 Lu, and 13 C+169 Tm systems are analyzed as a function of various physical parameters at a constant vrel ≈ 0.053c. It has been found that one neutron (1n) excess projectile 13 C (as compared to 12 C) results in less incomplete fusion contribution due to its relatively large negative α-Q-value, hence, α Q-value seems to be a reliable parameter to understand the ICF dynamics at low energies. In order to explore the reaction modes on the basis of their entry state spin population, the spin distribution of residues populated via CF and/or ICF in 16 O+159 Tb system has been done using particle-γ coincidence technique. CF-α and ICF-α channels have been identified from backward (B) and forward (F) α-gated γspectra, respectively. Reaction dependent decay patterns have been observed in different α emitting channels. The CF channels are found to be fed over a broad spin range, however, ICF-α channels was observed only for high-spin states. Further, the existence of incomplete fusion at low bombarding energies indicates the possibility to populate high spin states

Incomplete fusion studies in theF19+Tb159system at low energies and its correlation with various systematics

The excitation functions of reaction residues populated via the complete fusion and incomplete fusion process in the interaction of the $^{19}\mathrm{F}+^{159}\mathrm{Tb}$ system have been measured at energies $\ensuremath{\approx}4--6$ MeV/nucleon, using off-line $\ensuremath{\gamma}$-ray spectroscopy. The analysis of data was done within the framework of statistical model code pace4 (a compound nucleus model). A significant fraction of incomplete fusion was observed in the production of reaction residues involving $\ensuremath{\alpha}$ particle(s) in the exit channels, even at energies as low as near the Coulomb barrier. The incomplete fusion strength function was deduced from the experimental excitation functions and the dependence of this strength function on various entrance channel parameters was studied. The present results show a strong dependence on the projectile $\ensuremath{\alpha}$-Q value that agrees well with the existing data. To probe the dependence of incomplete fusion on entrance channel mass asymmetry, the present work was compared with the results obtained in the interaction of $^{12}\mathrm{C}, ^{16}\mathrm{O}$, and $^{19}\mathrm{F}$ with nearby targets available in the literature. It was observed that the mass asymmetry linearly increases for each projectile separately and turns out to be a projectile-dependent mass-asymmetry systematics. The deduced incomplete fusion strength functions in the present work are also plotted as a function of ${Z}_{P}{Z}_{T}$ (Coulomb effect) and compared with the existing literature. A strong dependence of the Coulomb effect on the incomplete fusion fraction was observed. It was found that the fraction of incomplete fusion linearly increases with ${Z}_{P}{Z}_{T}$ and was found to be more for larger ${Z}_{P}{Z}_{T}$ values indicating significantly important linear systematics.

Reconciliation of mass-asymmetry systematics for incomplete fusion

The onset and strength of incomplete fusion (ICF) has been studied in the framework of Morgenstern's mass-asymmetry systematics. The fraction of ICF has been deduced in 12C+169Tm system at energies ranging from 1.02Vb to 1.64Vb (Vb = 54.94 MeV from the analysis of excitation functions (EFs). It has been found that the ICF starts influencing complete fusion at noticeably lower, β-values (i.e., 0.025 or 2. 5% of c) than that proposed by Morgenstern (i.e., ≈ 6% of c). The fraction of ICF increases with entrance channel mass-asymmetry for individual projectiles, termed as projectile dependent mass-asymmetry (ProMass-) systematics. The proposed ProMass- systematics has withstood all tests that have been done for fairly large number of systems to verify its validness.

Observation of incomplete fusion at low angular momenta

Present work deals with experimental studies of incomplete fusion reaction dynamics using off-line γ -ray spectrometry at energies as low as ≈3-6 MeV/nucleon. Excitation functions for five reaction products populated via complete and/or incomplete fusion processes in 16 O+130 Te system have been measured and compared with the predictions of the statistical model code PACE4. A significant enhancement in the measured excitation functions compared to theoretical predictions for α -emitting channels has been observed and is attributed to incomplete fusion processes. The relative strength of incomplete fusion has been found to increase with projectile energy. Results show that incomplete fusion is associated even for angular momenta lesser than the critical angular momentum for complete fusion and also reveals importance of incomplete fusion even at energies as low as ≈3-6 MeV/nucleon.

Understanding the onset of incomplete fusion

The entrance channel effect on the onset and strength of incomplete fusion (ICF) has been studied in the present work. Several inclusive experiments have been performed to measure the ICF strength function in 12C,16O+169Tm systems at near and above barrier energies. Data obtained in these experiments suggest the existence of ICF even at slightly above barrier energies where complete fusion (CF) is supposed to be the sole contributor, and conclusively demonstrate strong projectile structure and energy dependence of ICF. The incomplete fusion strength functions for 160,12,13C+159Tb and 160,12,13C+181Ta systems are analyzed as a function of projectile α-Q-value at a constant νrel = 0.053c. It has been found that one neutron (1n) excess projectile 13C (as compared to 12C) results in less incomplete fusion contribution due to its relatively large negative α-Q-value. In order to understand the onset of ICF at such low energies, the driving input angular momenta (ℓ) involved in the production of different evaporation residues have been deduced from the analysis of experimentally measured spin-distributions for the same projectile-target combinations at the same incident energies. Higher ℓ-values, imparted into the system in non-central interactions, are found to be responsible for low energy ICF. The ICF-αxn/2αxn channels display involvement of higher ℓ-values than that observed in CF-xn/pxn/αxn/2αxn channels at the very same projectile energies. It has been observed that the mean value of ℓ increases with successively opened ICF channels and incident energy.

Experimental study of incomplete fusion reactions in theO16+Te130system below 6 MeV/nucleon

Background: The measurement and analysis of excitation functions may be used as an important tool to understand incomplete fusion reaction dynamics.Purpose: Several studies have been carried out to study incomplete fusion reactions at low energies, but a clear picture of incomplete fusion reaction processes at energies below 6 MeV/nucleon has yet to emerge. Further, there is no theoretical model which may give a good representation of incomplete fusion processes.Method: Off-line $\ensuremath{\gamma}$-ray spectrometry has been used to measure the excitation functions in the ${}^{16}\text{O}+{}^{130}\text{Te}$ system at energies $\ensuremath{\approx}3$--6 MeV/nucleon.Results: Excitation functions for five reaction products populated via complete and/or incomplete fusion processes in the $^{16}\mathrm{O}$ + $^{130}\mathrm{Te}$ system have been measured. Measured cross-sections have been compared with the predictions of the statistical model code pace4. A significant enhancement in the measured excitation functions compared to theoretical predictions for $\ensuremath{\alpha}$-emitting channels has been observed and is attributed to incomplete fusion processes. The relative strength of incomplete fusion has been found to increase with projectile energy. In the case of the $^{133}\mathrm{Xe}$($3\ensuremath{\alpha}n$) channel, the isomeric cross-section ratios have been deduced and found to increase rapidly with beam energy, indicating the importance of imparted angular momentum. The angular momentum at different energies has also been calculated. The analysis of the data indicates that incomplete fusion is associated even for angular momentum values smaller than the critical angular momentum for complete fusion. The results have been discussed in terms of the $\ensuremath{\alpha}$-cluster structure of the projectile for various fusion reactions.Conclusions: It may be concluded that, apart from complete fusion, incomplete fusion processes are of greater importance even at energies as low as $\ensuremath{\approx}$3-6 MeV/nucleon, where fusion evaporation channels are expected to be dominant. The measured isomeric cross-section ratio for the dominant incomplete fusion channel is found to increase with energy. Analysis of the data indicates that the incomplete fusion contribution becomes significant even for values of imparted angular momentum $\ensuremath{\ell}l{\ensuremath{\ell}}_{\mathrm{critical}}$ also, contrary to SUMRULE model predictions.

Influence of a one-neutron-excess projectile on low-energy incomplete fusion

Background: Incomplete fusion has been found to be an important contributor in light heavy-ion ($A\ensuremath{\le}20$) induced reactions even at slightly above barrier energies.Purpose: For better insight into the dynamics of incomplete fusion, the onset and influence of incomplete fusion need to be investigated in terms of projectile energy (${E}_{\mathrm{lab}}$) and entrance channel mass-asymmetry (${\ensuremath{\mu}}_{A}$). A rich set of experimental data on incomplete fusion may be useful to correlate the probability of incomplete fusion with the various entrance channel parameters and eventually to develop a theoretical model code for the same. Presently, there is no theoretical model available which can explain low-energy incomplete fusion data consistently.Methods: The excitation functions of complete and incomplete fusion residues populated in the $^{13}C$+$^{169}\mathrm{Tm}$ system have been measured using the recoil-catcher activation technique followed by offline $\ensuremath{\gamma}$ spectroscopy. The evaporation residues have been identified on the basis of characteristic $\ensuremath{\gamma}$ lines and confirmed through the decay-curve analysis.Results: The excitation functions of $xn$ and $pxn$ channels are found to be in good agreement with the statistical model code pace4; this suggests the population of these channels via complete fusion. Some residues are found to have a contribution from their higher charge isobar precursor decay. The precursor contribution has been deduced from the cumulative cross section using the standard successive radioactive decay formulations. The excitation functions of $\ensuremath{\alpha}$-emitting channels are observed to be significantly enhanced as compared to the statistical model code pace4. This enhancement may be attributed to the contribution from incomplete fusion. The incomplete fusion strength function for $^{13}C$+$^{169}\mathrm{Tm}$ is compared with that obtained in the $^{12}C$+$^{169}\mathrm{Tm}$ system. It has been found that the one-neutron (1$n$) excess projectile $^{13}C$ (as compared to $^{12}C$) results in a less incomplete fusion contribution due to its relatively large negative alpha-$Q$ value. Recently proposed ``alpha-$Q$-value systematics'' seems to explain incomplete fusion data.