The ${}_{}{}^6{}_{}{}^{}\mathrm{Li}(\alpha ,d){}_{}{}^8{}_{}{}^{}\mathrm{Be}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{}{}_{}{}^{}$ reaction is studied in the expectation that exchange contributions will be enhanced relative to the more usual light particle stripping process. Angular distributions of deuterons were measured at bombarding energies of 20 and 24 MeV and are found to exhibit back-angle peaking characteristic of the exchange process. Calculations including only a direct stripping mechanism are not able to account for the back-angle peaking and disagree with the back-angle data by more than two orders of magnitude. A two-mode finite-range distorted-wave Born-approximation analysis including cluster exchange contributions accurately describes the observed backward peaking at both energies. The importance of exchange contributions is attributed to favorable kinematic conditions and large cluster amplitudes associated with the exchange process.

NUCLEAR REACTIONS ${}_{}{}^6{}_{}{}^{}\mathrm{Li}(\alpha ,d)$, $E=20,24\mathrm{}$ MeV; measured $\sigma \left(\theta \right)$, $\theta =15\mathrm{}°-175°$. Enriched target. Two-mode, finite range DWBA analysis. ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$; calculated $\alpha \oplus \alpha$ radial function.

• Received 14 January 1974

DOI:https://doi.org/10.1103/PhysRevC.10.564