Sk Mustak Ali

The \(\alpha \)-transfer and breakup channels in \(^7\mathrm {Be}+^{12}\)C at 35 MeV are studied. The total cross sections from \(\alpha \)-transfer, populating different states of \(^{16}\)O are obtained. This work also presents the first exclusive breakup measurement of \(^7\)Be. In contrast to earlier works, the results show a significant contribution of breakup. Published by the Jagiellonian University 2026 authors

The measurement of the $^7$Be($d$,$^3$He)$^6$Li* transfer cross section at 5 MeV/u is carried out. The population of the 2.186 MeV excited state of $^6$Li in this reaction channel is observed for the first time. The experimental angular distributions have been analyzed in the finite range DWBA and coupled-channel frameworks. The effect of the $^7$Be($d$,$^3$He)$^6$Li reaction on both the $^6$Li and $^7$Li abundances are investigated at the relevant big-bang nucleosynthesis energies. The excitation function is calculated by TALYS and normalized to the experimental data. The $S$ factor of the ($d$,$^3$He) channel from the present work is about 50$\%$ lower than existing data at nearby energies. At big-bang energies, the $S$ factor is about three orders of magnitude smaller than that of the ($d,p$) channel. The ($d$,$^3$He) reaction rate is found to have a less than 0.1$\%$ effect on the $^{6,7}$Li abundances.

The ${}^{22}\mathrm{Ne}(p,\gamma ){}^{23}\mathrm{Na}$ capture reaction is a key step in the Ne-Na cycle of hydrogen burning. The rate of this reaction is critical in classical novae nucleosynthesis and hot bottom burning (HBB) processes in asymptotic giant branch (AGB) stars. Despite its astrophysical importance, significant uncertainty remains in the reaction rate due to several narrow low-energy resonances lying within and near the Gamow window. The present work revisits this reaction by examining the contribution of the 8664 keV subthreshold state and the 8945 keV doublet resonance state of $7/2^{-}$ configuration in ${}^{23}\mathrm{Na}$. Finite range distorted-wave Born approximation (FRDWBA) analysis of existing ${}^{22}\mathrm{Ne}({}^3\mathrm{He},d){}^{23}\mathrm{Na}$ transfer reaction data was carried out to extract the peripheral asymptotic normalization coefficients (ANCs) of the 8664 keV state. The ANC value obtained in the present work is $\approx 25\%$ higher compared to the previous work by Santra et al. [ Phys. Rev. C 101, 025802 (2020)]. Systematic $R$-matrix calculations were performed to obtain the nonresonant astrophysical $S$ factor utilizing the enhanced ANC value. The resonance strengths of the 8945 keV doublets were deduced from shell model calculations. The rate calculations are performed by omitting the resonances at $E_x=8862$, 8894, and 9000 keV, which are unlikely to exist as reported by Carrasco-Rojas et al. [ Phys. Rev. C 108, 045802 (2023)]. The total reaction rate is found to be $\approx 15–20\%$ higher at temperatures relevant for the HBB processes, compared to the recent rate measured by Williams et al. [ Phys. Rev. C 102, 035801 (2020)], and matches their rate at temperatures of interest for classical novae nucleosynthesis.

The anomaly in lithium abundance is a well-known unresolved problem in nuclear astrophysics. A recent revisit to the problem tried the avenue of resonance enhancement to account for the primordial ${}^7\mathrm{Li}$ abundance in standard big-bang nucleosynthesis. Prior measurements of the ${}^7\mathrm{Be}(d,p){}^8{\mathrm{Be}}^{*}$ reaction could not account for the individual contributions of the different excited states involved, particularly at higher energies close to the $Q$ value of the reaction. We carried out an experiment at HIE-ISOLDE, CERN to study this reaction at $E_{\mathrm{c}.\mathrm{m}.}=7.8\mathrm{MeV}$, populating excitations up to 22 MeV in ${}^8\mathrm{Be}$ for the first time. The angular distributions of the several excited states have been measured and the contributions of the higher excited states in the total cross section at the relevant big-bang energies were obtained by extrapolation to the Gamow window using the talys code. The results show that by including the contribution of the 16.63 MeV state, the maximum value of the total $S$ factor inside the Gamow window comes out to be 167 MeV b as compared to earlier estimate of 100 MeV b. However, this still does not account for the lithium discrepancy.