WEAK PROTON CAPTURE REACTIONS ON H-1 AND HE-3 AND TRITIUM BETA-DECAY

The cross sections for the weak proton capture reactions p + p --> d + e+ + nu-e and p + He-3 --> He-4 + e+ + nu-e have been calculated with realistic wave functions determined by using the Argonne upsilon-14 nucleon-nucleon interaction. To minimize the uncertainty in the axial exchange current operator, its matrix element has been adjusted so as to reproduce the measured Gamow-Teller matrix element for beta-decay of tritium. The exchange current contribution enhances the calculated rate of the pp capture reaction by 1.5% and decreases that of the p He-3 reaction by almost a factor of 5.