Alpha scattering and capture reactions in the<i>A</i>=7 system at low energies

Differential cross sections for $^{3}\mathrm{\ensuremath{\alpha}}$ scattering were measured in the energy range up to 3 MeV. These data together with other available experimental results for $^{3}\mathrm{He}$+\ensuremath{\alpha} and $^{3}\mathrm{H}$+\ensuremath{\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 $^{3}\mathrm{He}$(\ensuremath{\alpha},\ensuremath{\gamma}${)}^{7}$Be and $^{3}\mathrm{H}$(\ensuremath{\alpha},\ensuremath{\gamma}${)}^{7}$Li, and the branching ratios for the transitions into the two final $^{7}\mathrm{Be}$ and $^{7}\mathrm{Li}$ bound states, respectively. For $^{3}\mathrm{He}$(\ensuremath{\alpha},\ensuremath{\gamma}${)}^{7}$Be excellent agreement between calculated and experimental data is obtained. For $^{3}\mathrm{H}$(\ensuremath{\alpha},\ensuremath{\gamma}${)}^{7}$Li an 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=\ensuremath{\sigma}(${\ensuremath{\gamma}}_{1}$)/\ensuremath{\sigma}(${\ensuremath{\gamma}}_{0}$)\ensuremath{\approxeq}0.43 has been obtained.