arXiv subjects

Nishu Jain

Publications and source records attributed to Nishu Jain.

7 recordsLinked to original sources

arXiv2026

Competing decay modes and stability analysis of superheavy nuclei with Z = 120 using relativistic mean-field approach

We systematically study the competition between {\alpha}-decay and spontaneous fission in even-even superheavy nuclei with (Z=120) and 256 \leq A \leq 304 within the preformed cluster-decay model using microscopic inputs from relativistic mean-field calculations with the NL3 parameter set. The {\alpha}-decay half-lives are obtained from WKB barrier penetration with empirically determined preformation factors, self-consistent Q_{\alpha} values from RMF, and nuclear interaction potentials constructed using both M3Y and relativistic R3Y nucleon-nucleon forces, and are benchmarked against standard semi-empirical formulas. Our results predict reduced spontaneous fission probabilities and extended {\alpha}-decay chains toward the fermium region for isotopes with 296 \leq A \leq 304, with enhanced stability reflected in maxima of log_{10} T_{1/2} around neutron numbers N \approx 166-182. In particular, the nuclei 296,298,300,302,304_{120} are identified as the most favorable candidates for survival against fission, demonstrating the crucial role of shell effects, deformation, and pairing correlations and providing quantitative guidance for future experimental searches of Z=120 nuclei.

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arXiv2025

Exploring the role of low-lying intrinsic degrees of freedom and their impact on fusion cross-sections

The present work focuses on examining the low-lying intrinsic degrees of freedom and their impact on fusion dynamics. Fusion cross-sections were calculated using the coupled-channel code CCFULL for four specific reactions: $^{18}$O+$^{74}$Ge, $^{18}$O+$^{148}$Nd, $^{18}$O+$^{182}$W, and $^{18}$O+$^{186}$W, all conducted at energies below the Coulomb barrier across various energy levels. Vibrational and rotational features were studied concerning energy to distinguish their respective effects on fusion properties. The results indicate that the theoretical calculations for the nuclei $^{74}$Ge, $^{148}$Nd, $^{182}$W and $^{186}$W closely match the experimental data, particularly for the $2^+$ excited states. While slight discrepancies are observed for other excited states ($4^+$ and $6^+$), overall agreement remains significant. Additionally, the study reveals that hexadecapole deformation with different magnitudes have significant influences on the fusion cross-section. In cases where $\beta_4$ has a positive value, rotational levels beyond $6^+$ have minimal impact on the cross-section, resulting in a notable difference in the contribution of sequential channels. In contrast, for negative $\beta_4$ values, rotational energy levels up to the $2^+$ state substantially affect the fusion characteristics. Furthermore, the analysis extends to the estimation of the relative change ($\Delta\sigma_{fus}$) between the excited states and the ground state, both with and without considering coupling terms.

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arXiv2024

Relativistic mean-field study of alpha decay in superheavy isotopes with 100 \texorpdfstring{$\leq$ Z $\leq$}-120

The $α$-decay half-lives of superheavy nuclei with $100 \leq Z \leq 120$ are comprehensively analyzed using the axially deformed relativistic mean field (RMF) formalism for the NL3$^*$ parameter set. We employ RMF binding energies to determine the $α$-decay energies and make a comparison with both the available experimental data and the theoretical results obtained from the global nuclear mass model WS4. The four distinct formulae, specifically the modified scaling law Brown, modified Viola-Seaborg, Yibin {\it et al.} formula, and its modified form are used to calculate the decay half-lives and examine the numerical correlation between the half-life ($T_{1/2}$) for each $α$-decay energy. We notice that $T_{1/2}$ is significantly dependent on the decay formula in terms of isospin asymmetry and decay energy. We also noticed that modified scaling law Brown formula estimates of half-lives agreed comparatively better with the experiment as compared to others. Moreover, the present investigation provides significant information on the stability of the superheavy island considered for ongoing and/or future experiments.

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arXiv2023

Systematic study of the effect of individual rotational energy levels on the fusion cross-section of \texorpdfstring{$^{16}O$}--based reactions of range $480 \le {Z_PZ_T} \le 592$

The present work aims to investigate the effect of individual rotational energy levels on the fusion cross-sections for $^{16}$O-based reaction systems, namely, $^{16}$O + $^{182,184,186}$W, $^{16}$O + $^{176,180}${Hf}, $^{16}$O + $^{174,176}${Yb}, $^{16}$O + $^{166}${Er}, $^{16}$O + $^{148,152,154}$Sm, $^{16}$O + $^{150}$Nd at energies below the fusion barrier. Using the CCFULL code, the effect of low-lying rotational energy levels on the fusion cross-section for $^{16}$O induced reactions has been investigated at energies below and around the Coulomb barrier. The calculations are performed by assuming the fixed value of diffuseness parameter $a_{0}=0.65$ fm in the Woods-Saxon nuclear potential and the other two parameters are optimised by fitting the experimental data at the above barrier. Here we have determined the $V_0$ and $r_0$ as a function of $Z_PZ_T$, where experimental cross-sections are available. From our calculations, it is observed that the hexadecapole deformation ($β_4$) with different magnitudes has a significant influence on the fusion cross sections. For the case of the $+ve$ value of $β_4$, beyond $10^+$, the rotational levels cease to contribute significantly and also there is a significant difference between the contribution of sequential channels. On the other hand, in the case of -ve $β_4$, up to $6^+$ levels contribute significantly. Furthermore, we have established an algebraic systematic of fitting, which one can use to determine the parameters $V_0$, $r_0$ of Woods-Saxon nuclear potential within the range of $Z_PZ_T$ lie in between $480 \le {Z_PZ_T} \le 592$.

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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

Exploring the ground state bulk and decay properties of the nuclei in superheavy island

The $α$-decay half-lives of 204 superheavy nuclei covering the range $114 \leq Z \leq 126$ have been investigated using the relativistic mean-field model (RMF) for NL3$^*$ parameter set. The ground state bulk properties such as binding energy, quadrupole deformation parameter ($β_2$ ), and root-mean-square charge radii for these nuclei are analyzed. Four different semi-empirical formulae, namely, the universal decay law (UDL), the Viola-Seaborg (VSS) formula, the modified universal decay law (MUDL), and the modified Brown formula (MBrown), are used to obtain the $α$-decay half-lives for the considered nuclei. To examine the applicability of relativistic mean-field model within NL3$^*$ parametrization, the $α$-decay energies, and the half-lives of a few known superheavy nuclei within the range 102 $\leq$ Z $\leq$ 118 are calculated and the results are compared with the experimental data along with the theoretical predictions. The $α$-decay energies ($Q$-values) are estimated from the binding energies of the parent, and daughter from the RMF (NL3$^*$) parameter set. The calculated results are compared with macroscopic-microscopic Finite-Range-Droplet-Model (FRDM), Global Nuclear Mass Model (WS3, WS4), Weizsacker-Skyrme mass model (WS$^*$) predictions, and the experimental data, wherever available. The possible standard deviations are also estimated for experimental and various theoretical predictions. We find a good consistency for the experimental-to-UDL, FRDM-to-UDL, and WS4-to-UDL estimates of the decay energy and corresponding half-life. The present analysis provides the theoretical predictions within the microscopic model for the upcoming experiments on the superheavy region.

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arXiv2021

Structural and decay properties of nuclei appearing in the $α$-decay chains of $^{296,298,300,302,304}$120 within the relativistic mean-field formalism

An extensive study of $α$-decay half-lives for various decay chains of isotopes of $Z$ = 120 is performed within the axially deformed relativistic mean-field (RMF) formalism by employing the NL3, NL3$^*$, and DD-ME2 parameter set. The structural properties of the nuclei appearing in the decay chains are explored. The binding energy, quadrupole deformation parameter, root-mean-square charge radius, and pairing energy are calculated for the even-even isotopes of $Z$ = 100 $-$ 120, which are produced in five different $α$-decay chains, namely, $^{296}$120 $\rightarrow$ $^{260}$No, $^{298}$120 $\rightarrow$ $^{262}$No, $^{300}$120 $\rightarrow$ $^{264}$No, $^{302}$120 $\rightarrow$ $^{266}$No, and $^{304}$120 $\rightarrow$ $^{268}$No. A superdeformed prolate ground state is observed for the heavier nuclei, and gradually the deformation decreases towards the lighter nuclei in the considered decay chains. The RMF results are compared with various theoretical predictions and experimental data. The $α$-decay energies are calculated for each decay chain. To determine the relative numerical dependency of the half-life for a specific $α$-decay energy, the decay half-lives are calculated using four different formulas, namely, Viola-Seaborg, Alex-Brown, Parkhomenko-Sobiczewski, and Royer for the above said five $α$-decay chain. We notice a firm dependency of the half-life on the $α$-decay formula in terms of $Q_α$-values for all decay chains. Further, the present study also strengthens the prediction for the island of stability in terms of magic number at the superheavy valley in the laboratories.

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