Narrow Results

The asymptotic normalization coefficient (ANC) method is used to determine the cross sections of peripheral reactions at astrophysical energies because of existence of the Coulomb barriers. In this paper, we address an estimation of the ANC of ⁸B with its single particle wavefunction obtained within the framework of relativistic mean field (RMF) theory. We test the force parameters used in the RMF theory by comparing the calculated structure properties of A = 7–9 drip-line nuclei with experimental results. Utilizing the corrected bound wavefunction of ⁸B, the ANC is obtained and that indicates the S₁₇(0) is 18.07 eV b. Additionally, we find that the root-mean-square (rms) radius for the loosely bound proton in ⁸B is 3.98 fm. This confirms that ⁸B has a proton halo structure.

We have calculated astrophysical reaction cross-sections for $(\gamma ,\alpha )$ reactions of some nuclei important for the calculation of p-process reaction-decay network. Reaction rates for $\alpha$-induced reactions are calculated with the semi-microscopic optical potential constructed using double folding method, where nuclear density distributions for finite nuclei along with the effective nucleon–nucleon interaction are the important components of the folded potential. For this purpose, density distributions of target nuclei are obtained from relativistic mean field approach. Astrophysical reaction cross-section for elastic scattering of $\alpha$-particle from ${}^{92}\mathrm{\text{Mo}}$ target is compared with the existing experimental results to constrain the newly formed potential. Further, to check the credibility of the present theoretical framework, the astrophysical S-factor for $(\alpha ,\gamma )$ reactions are compared with the experimental observation, wherever available. Finally, an estimate of dominant photodisintegration channels at various astrophysical temperature is discussed for p-nuclei ${}^{74}\mathrm{\text{Se}}$ and ${}^{96}\mathrm{\text{Ru}}$.

A correct formula for fusion cross-section is proposed for better understanding of light nuclear fusion plasma. It is based on the one-dimensional method. The fusion cross-section and the Maxwellian rate parameters of the ³He+⁶Li system are calculated. The obtained results are in good accord with theoretical data of other researchers.

Astrophysical S-factors of radiative capture reactions on light nuclei have been calculated in a two-cluster potential model, taking into account the separation of orbital states by the use of Young schemes. The local two-body potentials describing the interaction of the clusters were determined by fitting scattering data and properties of bound states. The many-body character of the problem is approximatively accounted for by Pauli forbidden states. An important feature of the approach is the consideration of the dependence of the interaction potential between the clusters on the orbital Young schemes, which determine the permutation symmetry of the nucleon system. Proton capture on ²H, ⁶Li, ⁷Li, ¹²C and ¹³C was analyzed in this approach. Experimental data at low energies were described reasonably well when the phase shifts for cluster–cluster scattering, extracted from precise data, were used. This shows that decreasing the experimental error on differential elastic scattering cross-sections of light nuclei at astrophysical energies is very important also to allow a more accurate phase shift analysis. A future increase in precision will allow more definite conclusions regarding the reaction mechanisms and astrophysical conditions of thermonuclear reactions.

In this work, we explore the possibility that the motion of the deuterium ions emitted from Coulomb cluster explosions is highly disordered enough to resemble thermalization. We analyze the process of nuclear fusion reactions driven by laser–cluster interactions in experiments conducted at the Texas Petawatt laser facility using a mixture of D₂+³He and CD₄+³He cluster targets. When clusters explode by Coulomb repulsion, the emission of the energetic ions is “nearly” isotropic. In the framework of cluster Coulomb explosions, we analyze the energy distributions of the ions using a Maxwell–Boltzmann (MB) distribution, a shifted MB distribution (sMB), and the energy distribution derived from a log-normal (LN) size distribution of clusters. We show that the first two distributions reproduce well the experimentally measured ion energy distributions and the number of fusions from d–d and d-³He reactions. The LN distribution is a good representation of the ion kinetic energy distribution well up to high momenta where the noise becomes dominant, but overestimates both the neutron and the proton yields. If the parameters of the LN distributions are chosen to reproduce the fusion yields correctly, the experimentally measured high energy ion spectrum is not well represented. We conclude that the ion kinetic energy distribution is highly disordered and practically not distinguishable from a thermalized one.

The direct reaction component of the ${}^{19}$F($p,{\alpha }_0$) reaction at $E_{\mathrm{\text{cm}}}=180-600$keV is studied for the data that became very recently available. This component is significant in this work using the direct pickup model in the framework of the DWBA formalism and indicate the strong cluster structure of ${}^{19}$F. The direct component of astrophysical S-factor is calculated for ${}^{19}$F($p,{\alpha }_0$).

Nuclear fusion reactions at low energies ($E\sim 1$eV to few KeV) are crucial for the primordial nucleosynthesis of light elements. Nuclear fusion reactions in this energy window can be understood fruitfully in terms of quantum mechanical tunneling through the mutual Coulomb barrier of interacting nuclei. In this work, we studied the fusion cross-section, $\sigma$ and astrophysical S-factor in the selective resonant tunneling model (SRTM) approach for the $\mathrm{\text{p}}{+}^{15}$N and $\alpha {+}^{12}$C nuclear fusion reactions. We used space varying complex Gaussian type nuclear potential here. The quantum mechanical findings of the fusion cross-section, $\sigma$ and S-factor are in excellent agreement with the experimentally observed results found in the literature. The improved value of astrophysical S-factors for light nuclei may give a more clear picture of the elemental abundance in primordial nucleosynthesis.