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B. V. Carlson

Publications and source records attributed to B. V. Carlson.

At least 19 recordsLinked to original sources
arXiv2024

Role of nuclear deformation and orientation about symmetry axis of target nucleus on heavy-ion fusion dynamics

Nuclear shape and orientation degrees of freedom are incorporated into the calculation of the double-folding nuclear potential within the relativistic mean-field (RMF) formalism. The quadrupole deformations ($β_2$), nuclear densities and the effective nucleon-nucleon (NN) interaction potential are obtained using the RMF approach for the Hybrid, NL3$^*$ and NL3 parameterizations. The calculated quadrupole deformations are included in the target densities through the nuclear radius. The deformation and orientation-dependent microscopic nuclear potentials are further employed to obtain fusion barrier characteristics and cross-sections for 12 even-even heavy-ion reactions with doubly magic spherical $^{16}$O and $^{48}$Ca as projectiles along with deformed targets from different mass regions. The results obtained for the relativistic R3Y NN potential are compared with those of the Reid version of the non-relativistic M3Y NN potential as well as with the available experimental data. A decrease in the barrier height and increase in the cross-section is observed upon the inclusion of target quadrupole deformations in the nuclear density distributions at the target orientation angles, $θ_2\le58^\circ$ for the R3Y NN potential and at $θ_2\le60^\circ$ for the M3Y NN potential. On comparing the $θ_2$-integrated cross-section calculated using M3Y and R3Y NN potentials with spherical and deformed densities, one observes that the deformed densities and the relativistic R3Y NN potential obtained for the Hybrid parameter set provide better agreement with the available experimental data for all the considered reactions. Moreover, the modifications in the characteristics of the fusion barrier and hence in the cross-section with the inclusion of nuclear shape degrees of freedom and orientations are found to become more prominent in reactions forming heavier compound nuclei.

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arXiv2023

Reply to the "Comment on `Effect of density and nucleon-nucleon potential on the fusion cross section within the relativistic mean field formalism'"

In reply to the Comment made by M. V. Chushnyakova et al. on our paper [Phys. Rev. C 101, 044603 (2020)], we argue that the calculations, results and conclusions of our paper remain valid. We have shown here the calculations for one reaction using the deformed densities and the R3Y nucleon-nucleon potential obtained within the relativistic mean-field (RMF) formalism. Suitable clarications and justifications are given to address all the points raised in the Comment.

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arXiv2022

Medium dependent relativistic NN potential: Application to the fusion dynamics

In-medium effects are introduced in the microscopic description of the effective nucleon-nucleon (NN) interaction potential entitled DDR3Y in terms of the density-dependent nucleon-meson couplings within the Relativistic-Hartree-Bogoliubov (RHB) approach. The nuclear densities of the interacting target and projectile nuclei and NN potentials are obtained for non-linear NL3$^*$ and TM1 parameter sets within the relativistic mean-field approach and density-dependent DDME1 and DDME2 parameter sets within the Relativistic-Hartree-Bogoliubov (RHB) formalism. The DDR3Y NN potential and the densities are used to obtain the nuclear potential by adopting the double folding approach. This nuclear potential is further used to probe the fusion dynamics within the $\ell-$summed Wong model for a few {\it even-even} systems leading to the formation of light, heavy and superheavy nuclei. The calculations are also performed for the relativistic R3Y, density-dependent and independent M3Y interaction potentials for the comparison. We observed that the DDR3Y NN potential gives a better overlap with the experimental data as compared to non-relativistic M3Y and DDM3Y NN potentials. From the comparison of R3Y and DDR3Y interactions, it is manifested that the inclusion of in-medium effects in terms of density-dependent nucleon-meson couplings raises the fusion barrier and consequently decreases the fusion and/or capture cross-section. Moreover, the nuclear densities, as well as the relativistic R3Y NN potential obtained for the NL3$^*$ parameter set, are observed to give a comparatively better fit to the experimental data.

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arXiv2022

Nuclear fragmentation reactions as a probe of neutron skins in nuclei

We investigate the contributions of various reaction channels to the interaction, reaction, charge-changing and neutron-changing cross sections. The goal is to investigate the relation between microscopic interactions and the symmetry energy component of the equation of state (EoS) of interest for the structure of neutron stars. We have made a comparison of the neutron skins extracted from diverse experimental techniques with those obtained with Hartree-Fock-Bogoliubov calculations with 23 Skyrme and with 8 density-dependent interactions used in the relativistic mean field method. We have shown that no particular conclusion can be drawn on the best EoS in view of the wide range of uncertainty in the experimental data. We have further investigated the prospects of using neutron-changing reactions to assess the isospin dependence of the neutron-skin in neutron-rich nuclei.

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arXiv2022

Proton and neutron exchange as a prelude to fusion at near-barrier energies

Systematic examination of fusion for $^{39,41,45,47}$K + $^{28}$Si and $^{36,44}$Ar + $^{28}$Si provides insight into the impact of neutron and proton exchange on fusion for nuclei at and near the N=20 and N=28 shells. Comparison of the reduced excitation functions reveals a marked difference between the behavior of open-shell and closed-shell systems. While coupled channels calculations provide a good description for the closed-shell nuclei they significantly under-predict the fusion cross-section for open-shell nuclei. The observed trends are examined in the context of a potential energy surface, including shell effects, and multi-nucleon exchange with consideration of Pauli-blocking.

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arXiv2021

Inclusive Breakup Cross Sections in Reactions Induced by the Nuclides $^6$He and $^{6,7}$Li in the Two-Body Cluster Model

Calculations of inclusive $α$ particle production are performed to interpret reaction experimental data induced by the two-neutron halo $^6$He and the isotopes $^{6,7}$Li on different target nuclei. We have implemented the zero-range post-form DWBA to compute the elastic and nonelastic breakup cross sections. Integrated cross sections, angular distributions and spectra are presented. Projectiles are approximated as two-body clusters, namely $^6$He as $α$+dineutron and $^{6}$Li ($^{7}$Li) interpreted as $α$+deuteron(triton). The São Paulo optical potential is employed in the calculation of the distorted wave functions for the incident channels, while standard phenomenological interactions are used for the fragment-target interactions. Calculations for $^6$Li and $^7$Li furnish a good description of the data, while the reaction involving $^6$He is found to be a complicated case, where data interpretation is still considered a major obstacle. The present analysis identifies an overall large contribution from inclusive breakup emissions for all the cases studied.

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arXiv2021

The kinks in charge radii across $N$ = 82 and 126 revisited

We revisit the studies of the isotopic shift in the charge radii of {\it even-even} isotopes of Sn and Pb nuclei at $N$ = 82, and 126, respectively, within the relativistic mean-field and Relativistic-Hartree-Bogoliubov approach. The shell model is also used to estimate isotopic shift in these nuclei, for the first time, to the best of our knowledge. The ground state single-particle energies ($spe$) are calculated for non-linear NL3 \& NL3$^*$ and density-dependent DD-ME2 parameter sets compared with the experimental data, wherever available. We establish a correlation between the filling of single-particle levels and the isotopic shift in occupation probabilities. The obtained $spe$ from the relativistic mean-field and Relativistic-Hartree-Bogoliubov approaches are in line with those used in the shell model and experimental data for both the Sn and Pb isotopic chains. The shell model calculated isotopic shift agrees with relativistic mean-field and Relativistic-Hartree-Bogoliubov approaches that explain the experimental data quite well.

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arXiv2021

Neutron capture cross sections of radioactive nuclei

Alternative methods to calculate neutron capture cross sections on radioactive nuclei are reported using the theory of Inclusive Non-Elastic Breakup (INEB) developed by Hussein and McVoy [1]. The statistical coupled-channels theory proposed in Ref. [2] is further extended in the realm of random matrices. The case of reactions with the projectile and the target being two-cluster nuclei is also analyzed and applications are made for scattering from a deuteron target [3]. An extension of the theory to a three-cluster projectile incident on a two-cluster target is also discussed. The theoretical developments described here should open new possibilities to obtain information on the neutron capture cross sections of radioactive nuclei using indirect methods.

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arXiv2019

Systematical study of optical potential strengths in reactions involving strongly, weakly bound and exotic nuclei on $^{120}$Sn

We present new experimental angular distributions for the elastic scattering of $^6$Li$+^{120}$Sn at three bombarding energies. We include these data in a wide systematic involving the elastic scattering of $^{4,6}$He, $^7$Li, $^9$Be, $^{10}$B and $^{16,18}$O projectiles on the same target at energies around the respective Coulomb barriers. Considering this data set, we report on optical model analyses based on the double-folding Sao Paulo Potential. Within this approach, we study the sensitivity of the data fit to different models for the nuclear matter densities and to variations in the optical potential strengths.

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arXiv2019

Modeling photon--induced reactions on $^{233-238}$U actinide targets

Comprehensive calculations of cross sections of photon induced reactions on $^{233-238}$U targets for incident photon energies from 3 up to 30 MeV are undertaken with the statistical model code EMPIRE-3.2 Malta. Results are compared with the experimental data from EXFOR and with the current evaluations. The differences and the similarities between the models and parameters used in calculations of photon- and neutron-induced reactions on the same nuclei are discussed with focus on fission. The role of the extended optical model for fission in improving the description of the measured data and in determining consistent sets of barrier parameters is pointed out.

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arXiv2018

Weakly Bound Neutron-Rich Nuclei and Cosmic Phenomena

The single particle and bulk properties of the neutron-rich nuclei constrain fundamental issues in nuclear physics and nuclear astrophysics like the limits of existence of quantum many body systems (atomic nuclei), the equation of state of neutron-rich matter, neutron star, nucleosynthesis, evolution of stars, neutron star merging etc.. The state of the art of Coulomb breakup of the neutron-rich nuclei has been used to explore those properties. Unambiguous information on detailed components of the ground-state wave-function along with quantum numbers of the valence neutron of the nuclei have been obtained from the measurement of threshold strength along with the $γ$-rays spectra of the core following Coulomb breakup. The shape of this threshold strength is a finger-print of the quantum numbers of the nucleon. We investigated the ground-state properties of the neutron-rich Na, Mg, Al nuclei around N $\sim$ 20 using this method at GSI, Darmstadt. Very clear evidence has been observed for melting and merging of long cherished magic shell gaps at N = 20, 28. The evanescent neutron-rich nuclei imprint their existence in stellar explosive scenarios (r-process etc.). Coulomb dissociation (CD) is one of the important indirect measurements of the capture cross-section which may provide valuable input to the model for star evolution process, particularly the r-process. Some valuable bulk properties of the neutron-rich nuclei like the density dependent symmetry energy,neutron skin etc. play a key role in understanding cosmic phenomena and these properties have been studied via electromagnetic excitation. Preliminary results of electromagnetic excitation of the neutron-rich nucleus, $^{32}$Mg are presented.

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arXiv2018

Nuclear processes in Astrophysics: Recent progress

The origin of the elements is a fascinating question that scientists have been trying to answer for the last seven decades. The formation of light elements in the primordial universe and heavier elements in astrophysical sources occurs through nuclear reactions. We can say that nuclear processes are responsible for the production of energy and synthesis of elements in the various astrophysical sites. Thus, nuclear reactions have a determining role in the existence and evolution of several astrophysical environments, from the Sun to the spectacular explosions of supernovae. Nuclear astrophysics attempts to address the most basic and important questions of our existence and future. There are still many issues that are unresolved such as, how stars and our Galaxy have formed and how they evolve, how and where are the heaviest elements made, what is the abundance of nuclei in the universe and what is the nucleosynthesis output of the various production processes and why the amount of lithium-7 observed is less than predicted. In this paper, we review our current understanding of the different astrophysical nuclear processes leading to the formation of chemical elements and pay particular attention to the formation of heavy elements occurring during high-energy astrophysical events. Thanks to the recent multi-messenger observation of a binary neutron star merger, which also confirmed production of heavy elements, explosive scenarios such as short gamma-ray bursts and the following kilonovae are now strongly supported as nucleosynthesis sites.

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arXiv2018

Four-body eikonal approach to three-body halo nuclei scattering

Halo nuclei projectiles can undergo into a fragmentation process when scattered by a nucleus target. The corresponding core from exotic nuclei is usually observed while the others fragments of the reaction are not. We use the recently proposed theory by [Phys. Lett. B767, 53 (2017)] with a four-body description of the inclusive breakup reaction where the projectile is 20C described like a two-neutron halo nucleus. The momentum of both neutrons are integrated out giving a generic description of the core angular distribution. In this preliminary study we perform an analysis of the inclusive inelastic breakup cross-section using the eikonal approximation for the distorted wave function of the projectile. A study of the inclusive inelastic cross-sections of 20C from the collision with different targets are presented.

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arXiv2018

Post breakup dynamics of fragments produced in nuclear multifragmentation

The deexcitation of the primary hot fragments, produced in the breakup of an excited nuclear source, during their propagation under the influence of their mutual Coulomb repulsion is studied in the framework of a recently developed hybrid model. The latter is based on the Statistical Mul- tifragmentation Model (SMM), describing the prompt breakup of the source, whereas the particle emission from the hot fragments, that decay while traveling away from each other, is treated by the Weisskopf-Ewing evaporation model. Since this treatment provides an event by event descrip- tion of the process, in which the classical trajectories of the fragments are followed using molecular dynamics techniques, it allows one to study observables such as two-particle correlations and infer the extent to which the corresponding observables may provide information on the multifragment production mechanisms. Our results suggest that the framework on which these treatments are based may be considerably constrained by such analyses. Furthermore, they imply that information obtained from these model calculations may provide feedback to the theory of nuclear interferome- try. We also found that neutron deficient fragments should hold information more closely related to the breakup region than neutron rich ones, as they are produced in much earlier stages of the post breakup dynamics than the latter.

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arXiv2018

Exploring the decay probability of neutron-rich superheavy nuclei

The modes of decay for the even-even isotopes of superheavy nuclei of Z = 118 and 120 with neutron number $160 \leq N \leq 204$ are investigated in the framework of the axially deformed relativistic mean field model. The asymmetry parameter $η$ and the relative neutron-proton asymmetry of the surface to the center ($R_η$) are estimated for the ground state density distributions of the nuclei. We suggest that the resulting asymmetry parameter $η$ and the relative neutron-proton asymmetry $R_η$ of the density play a crucial role in the preformation factor of the decay half life.

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arXiv2018

Neck configuration of Cm and Cf nuclei in the fission state within relativistic mean field formalism

A correlation is established between the neutron multiplicity and the neutrons number in the fission state of Curium and Californium isotopes within a microscopic study using relativistic mean field formalism. The study includes the isotopes of Cm and Cf nuclei near the valley of stability, and hence is likely to play an important role in the artificial synthesis of superheavy nuclei. The static fission path, the neutron$-$proton asymmetry, the evolution of the neck and their composition in terms of nucleon numbers are also estimated. We find a maximum ratio for average neutron to proton density, which is about $1.6$ in the breakdown of the liquid$-$drop picture for $^{248}$Cm and $^{252}$Cf. A strong dependence of the neutron$-$proton asymmetry on the neutron multiplicity in an isotopic chain is also observed.

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arXiv2018

The surface properties of neutron-rich exotic nuclei within relativistic mean field formalisms

In this theoretical study, we establish a correlation between the neutron skin thickness and the nuclear symmetry energy for the even$-$even isotopes of Fe, Ni, Zn, Ge, Se and Kr within the framework of the axially deformed self-consistent relativistic mean field for the non-linear NL3$^*$ and density-dependent DD-ME1 interactions. The coherent density functional method is used to formulate the symmetry energy, the neutron pressure and the curvature of finite nuclei as a function of the nuclear radius. We have performed broad studies for the mass dependence on the symmetry energy in terms of the neutron-proton asymmetry for mass 70 $\leq$ A $\leq$ 96. From this analysis, we found a notable signature of a shell closure at $N$ = 50 in the isotopic chains of Fe, Ni, Zn, Ge, Se and Kr nuclei. The present study reveals an interrelationship between the characteristics of infinite nuclear matter and the neutron skin thickness of finite nuclei

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