Showing papers by "V. V. Parkar published in 2022"
TL;DR: In this paper , the authors measured the angular distribution and energy spectra of particles and deuterons through breakup, transfer and incomplete fusion processes to disentangle their relative contributions and investigate relative importance of breakup-fusion compared to transfer.
Abstract: Measurement of angular distributions and energy spectra of $\alpha$ and deuterons through breakup, transfer and incomplete fusion processes to dis-entangle their relative contributions and to investigate relative importance of breakup-fusion compared to transfer. Inclusive $\alpha$ production cross-sections have been measured for $^6$Li + $^{51}$V system near Coulomb barrier energies. Theoretical calculations for estimation of various reaction channels contributing to $\alpha$ production have been performed with finite range coupled reaction method using \textsc{FRESCO} code. The cross-sections from non-capture breakup (NCBU) ($\alpha$ + \textit{d}) and 1\textit{n}, 1\textit{p}, and 1\textit{d} transfer channels, compound nuclear decay channel and incomplete fusion (ICF) leading to $\alpha$ production were estimated to get the cumulative production cross-sections. Contributions from breakup, transfer and incomplete fusion channels could reproduce the integral direct $\alpha$ production cross-sections and their angular distributions quite well. The direct $\alpha$ production cross-sections are in agreement with other targets. The $\alpha$ production cross-sections are higher compared to the deuteron production. Kinematic analysis of the energy spectra of $\alpha$ particles and deuterons suggest that $\alpha$ particle spectra is dominated by breakp-fusion and deuteron spectra have contribution of breakup and transfer reactions. A systematic study of direct $\alpha$ production with various targets follow a universal behavior on average but noticeable differences are observed for different targets. A ratio of $\alpha$ and deuteron yields for a wide mass range of targets shows a saturation above barrier and an increasing production of $\alpha$ particles relative to deuteron around Coulomb barrier.
2 citations
TL;DR: Spectra of $\ensuremath{\alpha}$ particles were measured for several angles for a bombarding energy of 65 MeV to investigate various reaction mechanisms like direct break up and cluster transfer responsible for $\ensuresuremath{α}$ production as mentioned in this paper .
Abstract: Spectra of $\ensuremath{\alpha}$ particles were measured for $^{12,13}\mathrm{C} + ^{93}\mathrm{Nb}$ systems at several angles for a bombarding energy of 65 MeV to investigate various reaction mechanisms like direct break up and cluster transfer responsible for $\ensuremath{\alpha}$ production. The $\ensuremath{\alpha}$ spectra were analyzed in detail to determine the effect of $1n$ transfer on an $\ensuremath{\alpha}$-production cross section in particular. After accounting for contributions from direct breakup and Be transfer, there is a clear signature of the $\ensuremath{\alpha}$ particles produced through the break-up process following neutron transfer in the case of a $^{13}\mathrm{C}$ induced reaction. This is an interesting result being reported for the strongly bound projectile.
1 citations
TL;DR: In this paper , the authors studied the effect of deformation in multinucleon transfer processes at energies around the Coulomb barrier and 134 MeV, where the target nucleus is a well-established, deformed nucleus.
Abstract: Background: Multinucleon transfer reactions at energies around the Coulomb barrier offer a vital opportunity to study the rich physics of nuclear structure and dynamics, e.g., single-particle level structure and quantum shells, mass and charge equilibration processes, energy dissipation, as well as secondary decays via particle emission or fission. Despite the continuous development in the field, we still have limited knowledge about how deformation---one of the representative nuclear structures---affects multinucleon transfer reactions.Purpose: To develop our understanding of the reaction mechanism and to shed light on the effect of deformation in multinucleon transfer processes, we study the $^{16}\mathrm{O}+^{154}\mathrm{Sm}$ reaction at ${E}_{\mathrm{lab}}=85$ MeV (near the Coulomb barrier) and 134 MeV (substantially above the Coulomb barrier), where the target nucleus $^{154}\mathrm{Sm}$ is a well-established, deformed nucleus.Methods: We have performed experiments on the $^{16}\mathrm{O}+^{154}\mathrm{Sm}$ reaction at the BARC-TIFR pelletron-Linac accelerator facility, Mumbai, India, measuring angular distributions and $Q$-value spectra for various transfer products. The measured cross sections have been analyzed along with theoretical calculations based on the time-dependent Hartree-Fock (TDHF) theory, together with a statistical model for secondary deexcitation processes, $\mathrm{GEMINI}++$.Results: Angular distributions for elastic scattering and for various transfer channels were measured over a wide angular range. The $Q$-value- and angle-integrated isotope production cross sections have been extracted from the measured angular distributions. We obtained production cross sections for various isotopes for ${E}_{\mathrm{lab}}=85$ MeV, while only for four isotopes could be deduced for ${E}_{\mathrm{lab}}=134$ MeV due to present experimental limitations. For the lower incident energy case, we find a reasonable agreement between the measurements and the TDHF calculations for a-few-nucleon transfer channels; whereas TDHF underestimates cross sections for many-nucleon transfers, consistent with earlier works. On the other side, we find that calculated cross sections for secondary reaction products for the higher incident energy case qualitatively explains the measured trends of isotopic distributions observed for the lower energy. The latter observation indicates possible underestimation of excitation energies in the present TDHF $+$ GEMINI analysis. Although certain orientation effects were observed in TDHF results, it turns out to be difficult to disentangle them from the $Q$-value- and angle-integrated production cross sections.Conclusions: The present analysis highlights the deep-inelastic character of multinucleon transfer processes and importance of secondary deexcitation processes. We show that the orientation effect in multinucleon transfer processes in the $^{16}\mathrm{O}+^{154}\mathrm{Sm}$ reaction is rather weak and hard to disentangle from the present measured data. Further systematic investigations, especially in the subbarrier energy regime, where the data would be more sensitive to single-particle properties, would be required to uncover effects of nuclear deformation on multinucleon transfer processes in low-energy heavy-ion reactions.
1 citations
TL;DR: In this article , the authors investigated the relationship between breakup coupling and elastic scattering in a weakly bound projectile near the Coulomb barrier and measured the angular distribution and energy spectra of the particles produced through breakup, transfer, and complete fusion processes.
Abstract: Background: Experimental and theoretical investigation of breakup coupling effects due to different cluster structures ($^{8}\mathrm{Be}+n$ and $^{5}\mathrm{He}+\ensuremath{\alpha}$), relative importance of neutron or $^{5}\mathrm{He}/\ensuremath{\alpha}$ transfer, and their contribution to $\ensuremath{\alpha}$ production are important to understand reaction mechanism in a weakly bound projectile ($^{9}\mathrm{Be}$) near the Coulomb barrier.Purpose: Breakup coupling effect on elastic scattering and measurement of angular distributions and energy spectra of $\ensuremath{\alpha}$ particles produced through breakup, transfer, and complete fusion processes to disentangle their relative contributions and to investigate the relative importance of breakup followed by fusion (breakup-fusion) are compared to transfer.Methods: Elastic scattering, inclusive $\ensuremath{\alpha}$ production, lithium, and boron production cross sections have been measured for the $^{9}\mathrm{Be}+^{51}\mathrm{V}$ system above Coulomb barrier energies. Continuum-discretized-coupled-channels (CDCC) breakup coupling effect using $^{8}\mathrm{Be}+n$ and $^{5}\mathrm{He}+\ensuremath{\alpha}$ cluster configurations have been investigated. Coupled reaction channels (CRC) calculations for $1\mathit{p}, 1\mathit{d}$, and $1\mathit{n}$ stripping and $1\mathit{p}, 1\mathit{d}$ pickup leading to $^{8}\mathrm{Li}+^{52}\mathrm{Cr}, ^{7}\mathrm{Li}+^{53}\mathrm{Cr}, ^{8}\mathrm{Be}+^{52}\mathrm{V}$, and $^{10}\mathrm{B}+^{50}\mathrm{Ti}, ^{11}\mathrm{B}+^{49}\mathrm{Ti}$, respectively, were performed and compared with the experimental data. Theoretical calculations for the estimation of various reaction channels contributing to $\ensuremath{\alpha}$ production have been performed with CDCC and CRC methods using the fresco code.Results: Global optical model parameters for the $^{9}\mathrm{Be}$ projectile describe the elastic scattering data very well and the optical model fit improves the ${\ensuremath{\chi}}^{2}$ slightly. CRC calculations show a major contribution in the production of lithium through $1\mathit{p}, 1\mathit{d}$ stripping and boron through $1\mathit{p}, 1\mathit{d}$ pickup reactions. $\ensuremath{\alpha}$ production angular and energy distributions are obtained, and direct $\ensuremath{\alpha}$ production is described with contributions from noncapture breakup, breakup-fusion, and transfer reactions.Conclusions: Breakup coupling for $^{5}\mathrm{He}+\ensuremath{\alpha}$ and $^{8}\mathrm{Be}+n$ cluster structures shows a repulsive and attractive coupling effect on elastic scattering, respectively. The $^{8}\mathrm{Be}+n$ cluster structure also shows a dipole polarization effect by suppressing the Coulomb rainbow compared to the $^{5}\mathrm{He}+\ensuremath{\alpha}$ cluster structure. Kinematic analysis of the $\ensuremath{\alpha}$ particles energy spectra suggest that $\ensuremath{\alpha}$ production is dominated by breakup-fusion over cluster transfer. CRC calculations suggest that $1\mathit{p}, 1\mathit{d}$ stripping and pickup reactions are a major contributor to lithium and boron production cross sections.
1 citations
TL;DR: In this article , the excited states in the Br-Br nucleus were investigated through the fusion evaporation reaction at a beam energy of 90 MeV using the Indian National Gamma Array.
Abstract: The excited states in $^{73}\mathrm{Br}$ nucleus have been investigated through the fusion evaporation reaction $^{50}\mathrm{Cr}(^{28}\mathrm{Si}$, $\ensuremath{\alpha}p)^{73}\mathrm{Br}$ at a beam energy of 90 MeV using the Indian National Gamma Array. The $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidence technique has been used to add eight new $\ensuremath{\gamma}$-ray transitions in the level scheme. The mixing ratio of $\mathrm{\ensuremath{\Delta}}I=0$ (mixed with $E2$ and $M1$) transitions have been determined using angular distribution and ${R}_{\mathrm{DCO}}$-polarization measurement. The half-life of the ${9/2}^{+}$ isomeric state has been measured to be ${\ensuremath{\tau}}_{1/2}=52(2)$ ns from the variation in the intensity of delayed $\ensuremath{\gamma}$-ray transition as a function of coincidence time window. The two state mixing model calculations were performed to obtain the mixing amplitude, and mixing interaction of two different configurations of $^{73}\mathrm{Br}$. The calculated mixing amplitudes along with the deformations of two different configurations provide the monopole transition strength ${\ensuremath{\rho}}^{2}(E0)$ for Se, Br, and Kr isotopes in a semiempirical approach. These results support a prolate-oblate shape coexistence in the odd-$A\phantom{\rule{4pt}{0ex}}^{73}\mathrm{Br}$ nucleus. The observed structural properties have been discussed in terms of projected shell model calculations.
1 citations
TL;DR: In this article , the authors measured the total kinetic energy (TKE) and the mass of the fragment at excitation energies down to 16.7 MeV above the saddle point, and the observed width of the mass and TKE distributions agree well with the systematics based on liquid drop behavior.
Abstract: Fission fragment mass and total kinetic energy (TKE) distributions were measured for $^{12}\mathrm{C}+^{175}\mathrm{Lu}$ system at excitation energies down to 16.7 MeV above the saddle point. The overall mass and TKE distributions could be fitted with single Gaussian functions. The observed width of the mass and TKE distributions agree well with the systematics based on liquid drop (LD) behavior. The average TKE also shows parabolic dependence on fragment mass, as expected from LD behavior. Small contributions due to microscopic corrections from $Z\ensuremath{\approx}38$ and 45 shells can be extracted, if the widths of the LD component are fixed from systematics. Contrary to the theoretical predictions of substantial contributions from microscopic corrections, dominance of liquid drop behavior was observed.
1 citations
DOI•
TL;DR: In this article , a systematic analysis of the fusion cross sections around the Coulomb barrier energies with stable weakly bound ($6}$Li,$7}$ Li,$9}$Be) and strongly bound $12}$C projectiles on various targets was performed by using neutron flow model and coupled channels approach.
Abstract: A systematic analysis of the fusion cross sections around the Coulomb barrier energies with stable weakly bound ($^{6}$Li,$^{7}$Li,$^{9}$Be) and strongly bound $^{12}$C projectiles on various targets was performed by using neutron flow model and coupled channels approach. The analysis show that both the models are successful in explaining the near barrier fusion data. Further, it is also observed that the collective degrees of freedom as well as the neutron flow influence the near barrier fusion process involving weakly bound projectiles.
TL;DR: In this article , the elastic scattering angular distribution for weakly bound nucleus was measured at energies around the Coulomb barrier, and the optical model potential parameters for the system have been obtained from the extracted pure elastic scattering cross sections.
Abstract: Elastic scattering angular distribution for weakly bound nucleus $^{6}$Li on the deformed rare earth $^{159}$Tb target nucleus has been measured at energies around the Coulomb barrier. The elastic scattering cross sections for this reaction consist of inelastic contributions from low lying excited states of $^{159}$Tb. The pure elastic cross-sections have been extracted from the admixture of elastic and inelastic data. The optical model potential parameters for the system have been obtained from the extracted pure elastic scattering cross sections. Coupled channel calculations have been performed with this set of potential parameters, to compare the theoretical and experimental inelastic scattering cross sections. The work has been extended to obtain the spectroscopic factor for $^{158}$Tb+n configuration from the experimental 1n-pickup data.
TL;DR: In this paper , the contribution of one neutron stripping cross section to the total reaction cross section has been studied for 9Be projectile incident on 169Tm, 181Ta, 187Re and 197Au targets around Coulomb barrier energy.
DOI•
04 Nov 2022
TL;DR: In this article , the elastic scattering angular distribution for weakly bound nucleus 6 Li on the deformed rare earth 159 Tb target nucleus has been measured at energies around the Coulomb barrier.
Abstract: Elastic scattering angular distribution for weakly bound nucleus 6 Li on the deformed rare earth 159 Tb target nucleus has been measured at energies around the Coulomb barrier. The elastic scattering cross sections for this reaction consist of inelastic contributions from low lying excited states of 159 Tb. The pure elastic cross-sections have been extracted from the admixture of elastic and inelastic data. The optical model potential parameters for the system have been obtained from the extracted pure elastic scattering cross sections. Coupled channel calculations have been performed with this set of potential parameters, to compare the theoretical and experimental inelastic scattering cross sections. The work has been extended to obtain the spectroscopic factor for 158 Tb+n configuration from the experimental 1n-pickup data.