Determination of the 3He+alpha\to 7Be asymp. normalization coefficients (nucl. vertex constants) and their application for extrapolation of the 3He(alpha,gamma)7Be astroph. S-factors to the solar energy region

Abstract

A new analysis of the precise experimental astrophysical $S$-factors for the direct capture ${}^{3}He(\alpha ,\gamma {)}^7\mathrm{Be}$ reaction [B.S. Nara Singh et al., Phys.Rev.Lett. {\bf 93} (2004) 262503; D. Bemmerer et al., Phys.Rev.Lett. {\bf 97} (2006) 122502; F.Confortola et al., Phys.Rev. {\bf C 75} (2007) 065803 and T.A.D.Brown et al., Phys.Rev. {\bf C 76} (2007) 055801] populating to the ground and first excited states of ${}^7\mathrm{Be}$ is carried out based on the modified two - body potential approach in which the direct astrophysical $S$-factor, $S_{34}(E)$, is expressed in terms of the asymptotic normalization constants for ${}^3\mathrm{He}+\alpha {\to }^7\mathrm{Be}$ and two additional conditions are involved to verify the peripheral character of the reaction under consideration. The Woods--Saxon potential form is used for the bound ($\alpha {+}^3\mathrm{He}$)- state and the ${}^3\mathrm{He}\alpha$- scattering wave functions. New estimates are obtained for the "indirectly measured", values of the asymptotic normalization constants (the nuclear vertex constants) for ${}^3\mathrm{He}+\alpha {\to }^7\mathrm{Be}(g.s.)$ and ${}^3\mathrm{He}+\alpha {\to }^7\mathrm{Be}(0.429MeV)$ as well as the astrophysical $S$-factors $S_{34}(E)$ at E$\le$ 90 keV, including $E$=0. The values of asymptotic normalization constants have been used for getting information about the $\alpha$-particle spectroscopic factors for the mirror (${}^{7}L{i}^7\mathrm{Be}$)-pair.

27 pages, 11 figures, 2 tables