$\alpha -d$ correlations in quasi-elastic scattering of 23.6-MeV $\alpha$ particles on the deuteron cluster of the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ target were measured in and off the principal reaction plane. Despite the low c.m. energy of 14.2 MeV, the impulse approximation provides a reasonable description of the quasifree process. Computations were based on the asymptotic $\alpha -d$ $S$-state wave function and on the cluster-model wave function of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$. Insensitivity of the fits to the details of the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ cluster-model wave function indicates an extreme surface reaction mechanism. The full width at half-maximum of the spectator momentum distribution was found to be 48±6 MeV/c. By comparing the experimental cross section for the quasifree process at the maximum of the angular correlation ($\frac{d^2\sigma }{d{\Omega }_{d}d\Omega }=68\mathrm{}\pm 9$ mb/${\mathrm{sr}}^2$ at $\theta =25\mathrm{}°$,${\theta }_d=45\mathrm{}°$) with the corresponding cross section for the free process, the probability of finding ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ as an $\alpha -d$ cluster was evaluated.

• Received 18 July 1968

DOI:https://doi.org/10.1103/PhysRev.178.1706