Cross sections for the production of ${}_{}{}^6{}_{}{}^{}\mathrm{He}$, ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, and ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ produced in the $\alpha +\alpha$ reaction have been measured over the energy range 60—160 MeV. Detailed angular distributions are presented for exit channels leading to ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$, and ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(g.s.), along with cross sections for the three-body exit channels leading to the production of ${}_{}{}^6{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$. The astrophysical significance of the $\alpha +\alpha$ reaction is discussed with particular emphasis on the production of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ in the interaction of galactic cosmic rays with the interstellar medium. In addition, two-nucleon-transfer distorted-wave Born approximation calculations are presented in an attempt to understand the reaction mechanism operating in the $\alpha (\alpha ,d){}_{}{}^6{}_{}{}^{}\mathrm{Li}(\mathrm{g}.\mathrm{s}.\mathrm{})$ reaction.

NUCLEAR REACTIONS ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(${}_{}{}^4{}_{}{}^{}\mathrm{He}$,HI), HI=${}_{}{}^6{}_{}{}^{}\mathrm{He}$, ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, and ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$; $E=60-160\mathrm{}$ MeV; measured $\frac{d^2\sigma }{d\Omega \mathrm{dE}}$ and $\sigma \mathrm{}\left(E\right)\mathrm{}$; astrophysical relevance discussed; DWBA calculations for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(${}_{}{}^4{}_{}{}^{}\mathrm{He}$,$d$)${}_{}{}^6{}_{}{}^{}\mathrm{Li}$.

• Received 13 July 1981

DOI:https://doi.org/10.1103/PhysRevC.25.34