The production of ${\mathrm{Be}}^7$ in targets of oxygen, aluminum and copper bombarded with 30- to 42-Mev He ions has been studied using radiochemical techniques. At 40-Mev He-ion bombarding energy the formation cross sections are 2.4 mb, 0.22 mb, and 0.018 mb, respectively. For aluminum and oxygen targets the ${\mathrm{Be}}^7$ fragments are emitted sharply forward, implying a direct-interaction mechanism. Estimations of the energies of the ${\mathrm{Be}}^7$ fragments, along with the observation that for ${\mathrm{Al}}^{27}$ target the yield of ${\mathrm{Na}}^{24}$ is equal to the yield of ${\mathrm{Be}}^7$, suggests that in this particular case interaction involves the pickup of a ${\mathrm{He}}^3$ fragment from the nucleus by the impinging ${\mathrm{He}}^4$ ion with the deposition of less than 7 Mev of excitation energy in the ${\mathrm{Na}}^{24}$ residual nucleus.

• Received 7 May 1959

DOI:https://doi.org/10.1103/PhysRev.116.160