PROGRESS IN NUCLEAR ASTROPHYSICS USING SECONDARY-RADIOACTIVE BEAMS

We review progress in studying two central problems in nuclear astroph ysics: the C-12(alpha, gamma)O-16, Of importance for stellar processes in a progenitor star prior to a super-nova collapse and the Be-7(p, g amma)B-8 reaction rates at very low energies, of importance for estima ting the solar neutrino flux. Several attempts to constrain the p-wave S-factor of the C-12(alpha, gamma)O-16 reaction at Helium burning tem peratures (200 MK) using the beta-delayed alpha-particle emission of N -16 have been made. However, some discrepancy exists between the spect ra measured at Seattle and that of TRIUMF. We have improved our previo us Yale-UConn study of the beta-delayed alpha-particle emission of N-1 6 by improving our statistical sample (by more than a factor of 5), im proving the energy resolution of the experiment (by 20%), and in under standing our line shape, deduced from measured quantities. Our newly m easured spectrum of the beta-delayed alpha-particle emission of N-16 i s consistent with the Seattle('95) data, as well as an earlier experim ent performed at Mainz('71) and is not consistent with the TRIUMF('94) data. The implication of this discrepancies for the extracted astroph ysical p-wave S-factor is briefly discussed. The Be-7(p, gamma)B-8 rea ction is one of the major source of uncertainties in estimating the B- 8 solar neutrino flux and is critical for the solar neutrino problem. The main source of uncertainty is the existence of conflicting data wi th different absolute normalization. While attempts to measure this re action rate with Be-7 beams are under way we discuss a newly emerging method to extract this cross section from the Coulomb dissociation of the radioactive beam of B-8. We discuss some of the issues relevant fo r this study including the question of the E2 contribution to the Coul omb dissociation process which was recently measured to be small. The Coulomb dissociation appears to provide a viable alternative method fo r measuring the Be-7(p, gamma)B-8 reaction rate.