Measurements of the capture $\gamma$-radiation processes, $\mathrm{mass} 3+\alpha \to \mathrm{mass} 7+\gamma$ and $\mathrm{nucleon}+{\mathrm{Li}}^6\to \mathrm{mass} 7+\gamma$, give information about the cluster structure of the mirror nuclei ${\mathrm{Li}}^7$ and ${\mathrm{Be}}^7$. The cluster model predicts that the ground state and low excited states of these nuclei should have large reduced widths ${{\theta }_{3+4}}^2$ for the configuration $\mathrm{mass} 3+\alpha$ particle and small reduced widths ${{\theta }_{1+6}}^2$ for the configuration nucleon +${\mathrm{Li}}^6$. Scattering experiments provide accurate initial, capturing, wave functions, and an assumption of the cluster nature of the final, bound, states allows the electromagnetic capture cross sections to be calculated and compared to experiment. The reduced widths deduced show that ${{\theta }_{3+4}}^2$ is large, ${{\theta }_{1+6}}^2$ is small, and that the ground states and first excited states of ${\mathrm{Li}}^7$ and ${\mathrm{Be}}^7$ are primarily of the two-body cluster form $\mathrm{mass} 3+\alpha$ particle.

• Received 17 November 1960

DOI:https://doi.org/10.1103/PhysRev.122.224