Alpha scattering and capture reactions in the A = 7 system at low energies

Abstract

Differential cross sections for ${}^3$He-$\alpha$ scattering were measured in the energy range up to 3 MeV. These data together with other available experimental results for ${}^3$He $+\alpha$ and ${}^3$H $+\alpha$ scattering were analyzed in the framework of the optical model using double-folded potentials. The optical potentials obtained were used to calculate the astrophysical S-factors of the capture reactions ${}^3$He$(\alpha ,\gamma {)}^7$Be and ${}^3$H$(\alpha ,\gamma {)}^7$Li, and the branching ratios for the transitions into the two final ${}^7$Be and ${}^7$Li bound states, respectively. For ${}^3$He$(\alpha ,\gamma {)}^7$Be excellent agreement between calculated and experimental data is obtained. For ${}^3$H$(\alpha ,\gamma {)}^7$Li a $S(0)$ value has been found which is a factor of about 1.5 larger than the adopted value. For both capture reactions a similar branching ratio of $R=\sigma ({\gamma }_1)/\sigma ({\gamma }_0)\approx 0.43$ has been obtained.

Comments: submitted to Phys.Rev.C, 34 pages, figures available from one of the authors, LaTeX with RevTeX, IK-TUW-Preprint 9305402