The measurement of fusion cross sections from the ^9 Be induced reaction on ^93 Nb within the energy range of 20–46 MeV has been conducted using off-beam γ -ray spectroscopy. The measured excitation functions have been analyzed using equilibrium and pre-equilibrium reaction-based model codes to understand the underlying mechanisms. Additionally, the measured fusion excitation function was examined within the framework of the coupled-channel approach using the CCFULL code. Notably, the coupled-channel calculations, including couplings to inelastic states of the target and the projectile, yielded a satisfactory description of the sub-barrier fusion data. However, at energies above the barrier, the fusion cross section was observed to be suppressed by approximately 17

Background: Asymmetric mass splits observed in the extremely neutron-deficient (1.15 <= N/Z <= 1.55) lead-island isotopes brought much interest for the scientific community to explore this region. Although several experiments have been performed adopting beta-delayed fission and heavy-ion induced reactions, the role of shell effects associated with asymmetric fission is still not fully understood. Purpose: This article demonstrates the fission fragment mass distributions and associated fission fragment properties of Pt-186, populated via fusion of Si-28 with Gd-158, at three excitation energies (E*s). Further, a comparison of experimental mass distributions with the theoretical results has been carried out to test their prediction efficiency. Method: Thin layer of Gd-158 ((Gd2O3)-Gd-158) backed by the carbon was bombarded by Si-28 ions within 120-140 MeV laboratory energy. Time-of-flight information, provided by the two symmetrically placed multiwire proportional counters having an area of 200 cm(2), was utilized to get the velocities, which were further used to estimate the fission fragment mass and kinetic energy distributions. Results: A single Gaussian could not satisfactorily fit the flat-topped mass distribution at each excitation energy. Later, the two- and three-Gaussian fits efficiently reproduced the distributions, signifying the crucial role of the quadrupole deformed (Z approximate to 34, 36, 42, 44, and 46) shell gaps in deciding the fate of compound nucleus's disintegration. No signature of the quasifission process has been observed in this study. Moreover, an increment in the symmetric contribution with increasing E* is spotted experimentally as well as theoretically for the present system. Further, a comparison with the nearby Pt isotopes revealed the symmetric contributions decrease with decreasing neutron number. To some extent, GEneral Fission (GEF) model is found to predict the fragment properties of the present system. Conclusions: The structure observed in the middle section of the mass distribution confirms the presence of an asymmetric mode along with the symmetric mode. The extracted Zpeak values are influenced by the deformed shell gaps. GEF-predicted Z(peak) values, N-peak values, and symmetric contributions are observed to agree with the experimental results.

The measurement of fusion cross sections from the Be-9 induced reaction on Nb-93 within the energy range of 20-46 MeV has been conducted using off-beam gamma-ray spectroscopy. The measured excitation functions have been analyzed using equilibrium and pre-equilibrium reaction-based model codes to understand the underlying mechanisms. Additionally, the measured fusion excitation function was examined within the framework of the coupled-channel approach using the CCFULL code. Notably, the coupled-channel calculations, including couplings to inelastic states of the target and the projectile, yielded a satisfactory description of the sub-barrier fusion data. However, at energies above the barrier, the fusion cross section was observed to be suppressed by approximately 17% compared to the predictions made by the coupled-channel calculations.

In heavy-ion collision experiments, the fusion cross section in the sub-barrier energy region is found to be enhanced by several orders of magnitude in comparison to the prediction of the one-dimensional barrier penetration model (1D-BPM) that involves the quantum mechanical tunneling effect during fusion. So far, the coupling-aided tunneling due to participating nuclei’s intrinsic degrees of freedom continues to be identified as an accountable factor. We intend to probe the role of structural properties and low-lying inelastic excitations of the colliding nuclei in driving the fusion phenomenon for energies in the near and sub-barrier regions. In the study, the fusion excitation function has been measured for ^30Si+^140Ce reaction for energies ≈ 11

The state-of-the-art technologies made it possible to reach the realms of fusion between two complex nuclei that offer an opportunity to explore a diverse spectrum of fusion phenomena. In this article, we have reported the influence of positive Q-value neutron transfer (PQNT) channels in fusion dynamics. Significant enhancement in sub-barrier fusion cross section has been observed for the Si-28+Gd-158 as compared to Si-30+Ce-140 and other similar systems with nearby mass asymmetry. Current findings include a comparison of the fusion excitation function of multiple systems on a reduced scale. The study sheds light on the influence of PQNT channels and deformation in nuclei on the sub-barrier fusion phenomenon. Further, fusion barrier parameters (barrier height and radius) extracted from the measured data demonstrate a good agreement with the empirical parameterization and proximity potential models.

Background: Asymmetric fission in sublead nuclei, especially mercury and platinum isotopes, has generated keen interest in studying fission in A < 200 mass region. The role of proton and neutron shells on asymmetric fission in these nuclei is still under test and requires more investigation.Purpose: This paper presents measurements aimed at studying the fission modes of 192Hg formed in the reaction 32S + 160Gd in the excitation energy range 54-74 MeV. Method: Mass distributions have been determined from the fission fragments' (FF) time of flight (TOF). Two multiwire proportional chambers were placed symmetrically on opposite sides of the beam to cover the folding angle for symmetric fission. The measured TOF of the fission fragments was used to obtain their velocities, and after clean separation of compound nuclear fission events, the velocities were further used to obtain the fission fragment mass and total kinetic energy (TKE) distribution.Results: The fission fragment mass distributions at all beam energies were found to be characteristically flat topped, which deviates significantly from a single Gaussian behavior. The distinctive features of mass and energy distributions happen to be explained by the presence of a symmetric fission mode and three asymmetric fission modes, manifested by different total kinetic energies in varying mass regions. These asymmetric fission modes are a consequence of the stabilization role of proton shells at Z approximate to 36, Z approximate to 46, and Z = 28/50. The most probable mass of light and heavy fragments are found to be around 86 and 106 u, respectively. The symmetric yield is found to increase with the excitation energy.Conclusions: The present study indicates a mixture of symmetric and asymmetric modes in the fission of 192Hg nuclei and points out the relevance of deformed proton shells at Z approximate to 36 and 46.

The challenging task in heavy-ion collisions is unambiguously identifying the true fusion events in the deep sub-barrier region. Considering the primary challenge, we have measured fusion excitation functions for Si-28+ Gd-158 reaction at energies above to deep sub-barrier region to decipher the role of multineutron transfer with positive Q value and fusion hindrance in an asymmetric system. A comparison has been made with our previous measurement for Si-30+ Gd-156 system where only one transfer channel with Q > 0 exists and populates the same compound nucleus Pt-186 *. The enhancement in fusion cross sections is observed on a reduced scale in the Si-28+ Gd-158 reaction over Si-30+ Gd-156 system at sub-barrier energies. The measured fusion data and extracted barrier distribution have been analyzed within the framework of coupled-channels (CC) programs, CCFULL and empirical channel coupling. Coupling to rotational excitations in projectile and target along with up to 2n transfer channel with positive Q value is found to be promising to explain the fusion excitation functions except for the lowest energy point. However, the influence of more than two neutrons transfer is insignificant in Si-28+ Gd-158 system. At the lowest energy (approximate to 14% down the Coulomb barrier), a deviation from standard CC has been found, which may indicate the threshold for fusion hindrance, but additional lower-energy data are needed to prove this. The experimental threshold energy (E-S) for fusion hindrance is in good agreement with the empirical formula, and it is consistent with the observed pattern of E-S as a function of the entrance channel parameter (zeta) for other nearly symmetric and asymmetric systems.

More focused investigations are required to better understand the different modes of fusion phenomena in weakly bound projectiles. In order to comprehend the reaction mechanism of weakly bound projectiles, a new measurement of the evaporation residue cross sections from the Li-6-induced reaction on Ta-181 in the 4.5-7.1 MeV/nucleon energy range has been reported in this article. The gamma-ray spectrometry has been employed to identify the Os-183m,Os-g , Os-182, Re-183, and Ta-183,Ta-182m2,Ta-180 residues produced in the reaction via different evaporation channels. The EMPIRE-3.2.2 code, which houses both the equilibrium and pre-equilibrium models in its framework, and PACE4 have been tasked to analyze the measured excitation functions. Out of the two, EMPIRE-3.2.2 demonstrates better agreement with the data. A systematic analysis of the measured data and theoretical background indicates that the complete and incomplete fusion of Li-6 contribute to the residual cross sections. Thus, the strength of the partial fusion has been inferred. Further, the neutron transfer channels have been found to contribute significantly to the reaction dynamics; hence they are investigated using the coupled reaction channel calculations and discussed in detail. The isomeric cross section ratio obtained from the measured residual cross sections of the isomeric pair of Os-183 highlights the significance of angular momentum and relative spins of the ground and isomeric states as a function of projectile incident energy.

The present work reports an analysis of the production yield of residues from the 6Li ＋ 181Ta reaction in a low-energy regime. The experimental yield of 183gOs, 183mOs, 182Os, 183Re, 183Ta, 182m2Ta, and 180Ta have been measured in the 27–43 MeV energy window and compared with equilibrium and pre-equilibrium model calculations under the framework of the nuclear reaction model code, EMPIRE-3.2.2. The maximum yield measured for 183gOs is 80.5 ± 14.9 MBq/C at 40.2 MeV energy in a 2.3 mg/cm2 thick Ta target corresponding to a cross-section of 360.1 ± 34.4 mb from the 181Ta(6Li,4n)183Os reaction and that for 183Re is 1.36 ± 0.4 MBq/C at 42.75 MeV in a 2.4 mg/cm2 thick target. The model estimations agree well with the experimental yields of 183gOs and 183Re. The possible production of stable residues has been estimated using the model-predicted cross-section in the studied energy range. A comparison of production yields of 183m,gOs from 6Li- and 7Li-induced reaction on Ta demonstrates the 6Li reaction as a better candidate. Thick target yields have been evaluated for Os and Re isotopes.

Background: Advancement in accelerator facilities has opened the door to dig deep to understand the interplay between nuclear reactions and structures. Although the influence of inelastic excitations on nuclear scattering and sub-barrier fusion is somewhat established, a clear understanding of nucleon transfer with a positive-Q value is yet to achieve. Purpose: The objective of this paper is to examine the role of the 2n-transfer channel with a positive Q value on sub-barrier fusion and back-angle quasielastic (QE) scattering in the 30Si + 156Gd reaction. Furthermore, extraction of barrier distributions (BDs) from fusion and QE scattering to infer their shapes is also a prime goal. Method: The excitation functions (EFs) of fusion and back-angle QE scattering have been measured over a wide range of incident beam energy around the Coulomb barrier using a recoil mass spectrometer. Furthermore, BDs have been extracted using the measured fusion and back-scattered QE data. The underlying findings have been analyzed within the framework of coupled-channel (CC) formalism using CCFULL and ECC programs. Results: Fusion enhancement has been observed compared to those predicted from the one-dimensional barrier penetration model at sub-barrier energies. Fusion enhancement and QE EFs are explained by CC predictions considering the collective excitations among the colliding nuclei. The inclusion of 2n transfer and collective excitations in CCFULL improves the fit to the experimental fusion data in a short span of energy window around the Coulomb barrier, whereas no significant effect has been observed at the sub-barrier region. However, no such effect of 2n-pickup transfer has been observed from ECC model calculations. Thus, no firm conclusion can be made on the role of 2n-pickup transfer with a positive Q value in present measurements. Conclusion: Fusion EFs have been successfully explained by the CC calculations using CCFULL and ECC model codes. No significant effect of the 2n-pickup channel with a positive Q value was observed on sub-barrier fusion enhancement. However, QE EFs are reproduced by considering the collective excitations and 2n-transfer channel couplings. Fusion and QE BDs are similar in shape within the experimental uncertainty. One-dimensional barrier parameters extracted from the measured data agree with the different theoretical models. Also, the present system obeys the systematic based on deformation values after transfer at the exit.

Background: Advancement in accelerator facilities has opened the door to dig deep to understand the interplay between nuclear reactions and structures. Although the influence of inelastic excitations on nuclear scattering and sub-barrier fusion is somewhat established, a clear understanding of nucleon transfer with a positive-$Q$ value is yet to achieve.Purpose: The objective of this paper is to examine the role of the $2n$-transfer channel with a positive $Q$ value on sub-barrier fusion and back-angle quasielastic (QE) scattering in the $^{30}\mathrm{Si}+^{156}\mathrm{Gd}$ reaction. Furthermore, extraction of barrier distributions (BDs) from fusion and QE scattering to infer their shapes is also a prime goal.Method: The excitation functions (EFs) of fusion and back-angle QE scattering have been measured over a wide range of incident beam energy around the Coulomb barrier using a recoil mass spectrometer. Furthermore, BDs have been extracted using the measured fusion and back-scattered QE data. The underlying findings have been analyzed within the framework of coupled-channel (CC) formalism using ccfull and ecc programs.Results: Fusion enhancement has been observed compared to those predicted from the one-dimensional barrier penetration model at sub-barrier energies. Fusion enhancement and QE EFs are explained by CC predictions considering the collective excitations among the colliding nuclei. The inclusion of $2n$ transfer and collective excitations in ccfull improves the fit to the experimental fusion data in a short span of energy window around the Coulomb barrier, whereas no significant effect has been observed at the sub-barrier region. However, no such effect of $2n$-pickup transfer has been observed from ecc model calculations. Thus, no firm conclusion can be made on the role of $2n$-pickup transfer with a positive $Q$ value in present measurements.Conclusion: Fusion EFs have been successfully explained by the CC calculations using ccfull and ecc model codes. No significant effect of the $2n$-pickup channel with a positive $Q$ value was observed on sub-barrier fusion enhancement. However, QE EFs are reproduced by considering the collective excitations and $2n$-transfer channel couplings. Fusion and QE BDs are similar in shape within the experimental uncertainty. One-dimensional barrier parameters extracted from the measured data agree with the different theoretical models. Also, the present system obeys the systematic based on deformation values after transfer at the exit.

Fusion phenomena in heavy-ion reactions involving all kinds of projectile and target are still an engrossing quest due to the appearance of numerous mass and energy sharing processes. Hitherto, it is required to have more experimental studies to contemplate fusion mechanisms, which are necessary to unfold. In this endeavour, for the first time, a measurement of residual cross sections from $$^6$$ Li induced reaction on $$^{\text {nat}}$$ Cu has been presented in this article within the 3.6–7.1 MeV/nucleon energy range. The residues $$^{69,67,66}$$ Ge, $$^{68,67,66,65}$$ Ga, and $$^{65,63,62}$$ Zn produced in the reaction have been identified by the $$\gamma $$ -ray spectroscopy. The measured excitation function of the residues has been analyzed using equilibrium and pre-equilibrium reaction models in the framework of PACE4, EMPIRE-3.2.2 and ALICE20 to understand the reaction mechanisms involved in the low energy region. The study indicates that the admixture of equilibrium and pre-equilibrium mechanisms indeed explains the measured residual cross sections. An estimate on the production of medically relevant $$^{68}$$ Ga has also been made.

Nuclear reaction induced by a weakly bound projectile on light-medium mass targets poses open questions on the fusion mechanism. It is seen that fusion suppression in such reactions is negligible, but that stands on the basis of scarcely available experimental data. Thus more experimental data are demanded to bring out a clear understanding. In the course of this, for the first time, a measurement of residual cross sections from Li-7 induced reaction on Cu-nat has been presented in this article within the 2.3-6.0 MeV/nucleon energy range. The residues Ge-69,Ge-67,Ge-66, Ga-68,Ga-67,Ga-66,Ga-65, and Zn-69m(,6)5,63 produced in the reaction have been identified by gamma-ray spectroscopy. The measured excitation function of the residues has been analyzed using equilibrium and preequilibrium reaction models in the framework of EMPIRE-3.2.2 to understand the reaction mechanisms involved in the low energy region. The underlying reaction mechanism is shown to be a blend of equilibrium and preequilibrium processes. The intensity of the gamma-peak 93.31 keV arising in the decay of Ga-67 has been revised experimentally. The experimental intensity turns out to be about half the value reported in different nuclear databases. Fusion cross sections have been estimated using the experimental data and EMPIRE-3.2.2 code. The estimated fusion cross sections are in line with coupled channel calculations taking inelastic excitations into account. The large production cross section of medically important Ga-67 has been measured.

Background: The measured subbarrier fusion cross sections in heavy-ion reactions are found to be significantly large as compared with those expected from the one-dimensional barrier penetration model (1d-BPM). Although attempts have been made to comprehend the enhancement in terms of different intrinsic degrees of freedom of the colliding nuclei, a clear understanding of the same is yet to come. Purpose: The objectives of this study is to understand the interplay of the channel coupling effect on fusion excitation function and explore the decay dynamics of the excited compound nucleus in the sub-and-near barrier region. Method: Fusion excitation function has been measured at energies from 7% below to 38% above the Bass barrier using a recoil mass spectrometer. Furthermore, cross sections of the different evaporation residues, such as 98, 99, 100, and 101 u, have been extracted. Results: The observed enhancement in the subbarrier fusion cross sections over the 1d-BPM predictions has been explained by considering the low-lying inelastic excitations among the interacting partners using ccfull code and by the barrier modification using the dynamical cluster-decay model (DCM). The cross sections of individual residual mass fractions (98, 99, 100, and 101 u) have been compared with the Hauser-Feshbach model. Conclusion: Coupled-channel calculations and DCM have successfully explained the total fusion cross sections data. The measured total fusion cross section sigma(fus) was found to be approximately equal to the sum of various residual mass fractions (Sigma sigma(ER)) at energies above the Bass barrier. One-dimensional barrier height and radius parameters extracted from the measured data are in good agreement with the Bass model and DCM parameters.