Thermonuclear Reactions of Light Nuclei in Astrophysical Plasmas.

This dissertation consists of two parts. In Part A, we present a very detailed and extensive calculation on the proton-proton fusion reaction, which takes place in the (high-temperature) central regions of young stars such as the sun. A summary of the previous formulations of and results for the reaction rate is presented, and is then followed by our own calculations and results. Our treatment consists of a recalculation of the Lambda ^2 and S factors (defined therein) using different deuteron and p-p wavefunctions, but also includes evaluations of the various uncertainties attached to the determination of these quantities. The last two sections of this first part deal with the corrections one must apply to the (simplest) calculation of the reaction rate, and with the relevance of these new results to the expected fluxes of the solar neutrinos. Part B of this thesis treats the thermonuclear breakup processes which occur in astrophysical plasmas of ion temperatures kT_{rm i } > 1 MeV, and investigates some of their notable consequences. The first four chapters of this second part consist of calculations of the rates of breakup of the (relevant) light species, as induced by protons, alphas, photons, and neutrons and electrons, respectively. These chapters include considerations of the importance of the density and the available time for reaction as well as comparisons of the different types of processes. Applications and consequences of such reactions are treated in the fifth chapter of Part B. We first consider the possibility of occurrence and the importance of these processes in accretion plasmas existing around compact stars (BHs, NSs, and WDs). We then show the significance of these reactions with regard to gamma-ray line emissivities from high-temperature plasmas. We also use these emissivity considerations to suggest a way for determining the temperature and density of (and possibly even their distribution in) the plasma. The production of certain gamma-lines in the breakup reactions themselves is also mentioned as a direct effect (and thus a possible observational confirmation) of the breakup processes. Other applications are briefly mentioned at the end of this final chapter.