Theoretical Study of Some Processes of CNO Cycle

Abstract

In order to know about the star, their composition, and the energy generated inside it, one need to know about the nuclei and the reactions which they go through. Nucleosynthesis is one of the key process for the formation of low mass nuclei. The present dissertation is based on two types of processes i.e., the radiative capture and weak interactions. Different nuclear reactions take place in the CNO cycle. We calculated the nuclear cross-section, astrophysical S-factor and rates during the formation of low mass nuclei like 10B, 13N, 14N, 14O, and the decay of 13N to 13C. We used the single-particle potential model for the calculation of both bound states and scattering states wave-function of 10B, 13N, 14N and 14O. For the calculation of the bound-state wave-functions of 10B and 14N, we used the modified form of the nuclear potential (Woods-Saxon potential). We took into account only E1 transitions. The capture cross-sections were taken into account as the direct and resonance transitions in case of 10B, 13N, 14N, and 14O. For the case, where the resonance width was narrow, we used the none-resonance capture cross-section, which is added to the total amplitude. For the case, where the resonance width was broad (410±20 keV) and the potential model got fail like in the case of 14N, we used the R-matrix approach. The measured data were taken from the pre-existing data of proton width, radiative width and resonance width. In all the cases, the model based computed nuclear cross-sections and nuclear reaction rates are in good agreement with experimental data. We discuss the importance of taking into account the spectroscopic factor in the calculation of the half-life and logf t beta decay of nuclei containing one nucleon in the outer-most shell. We pointed out the dominant role of the asymptotic normalization coefficient that takes into account the many particle effect and allows us to obtain the spectroscopic factor necessary to describe the reaction 13N −→ 13C + β + + νe. We have used the overlap functions, instead of single-particle functions, for the best fitting of our computed data with the experimental results of beta decay half-life and logf t values.