ASTROPHYSICAL REACTION-RATES FOR B-10(P,ALPHA)BE-7 AND B-11(P,ALPHA)BE-8 FROM A DIRECT MODEL

The reactions B-10(p,alpha)Be-7 and B-11(p,alpha)Be-8 are studied at t hermonuclear energies using DWBA calculations. For both reactions, tra nsitions to the ground states and first excited states are investigate d. In the case of B-10(p,alpha)Be-7, a resonance at E(res) = 10 keV ca n be consistently described in the potential model, thereby allowing t he extension of the astrophysical S-factor data to very low energies. Strong interference with a resonance at about E(res) = 550 keV require a Breit-Wigner description of that resonance and the introduction of an interference term for the reaction B-10(p,alpha(1))Be-7. Two isosp in T = 1 resonances (at E(res1) = 149 keV and E(res2) = 619 keV) obser ved in the B-11 + p reactions necessitate Breit-Wigner resonance and i nterference terms to fit the data of the B-11(p,alpha)Be-8 reaction. S -factors and thermonuclear reaction rates are given for each reaction. The present calculation is the first consistent parametrization for t he transition to the ground states and first excited states at low ene rgies.