Nuclear Reactions in the Stars. I. Proton-Proton Chain

The rates are calculated for the main reactions making up the "proton-proton chain, " whose net effect is the conversion of four hydrogen atoms into one helium atom. These calculations are carried out for temperatures and densities corresponding to central conditions in main sequence stars. The mean reaction rate for the beta-decay conversion of two protons into one deuteron is calculated accurately, using the latest data on the two-nucleon system and on beta-decay. It is shown that, under normal stellar conditions, the reaction chain is completed by the radiative capture of a proton by a deuteron and by the collision between two of the resultant He^3 nuclei to form one He^4 nucleus and two protons. Values are given for the rate of energy production and for the concentrations of deuterium and He^3 at various temperatures.