We have measured excitation functions for production of ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ by $d$-, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-, and $\alpha$-particleinduced reactions in carbon using the stacked-foil method. Similar measurements for protons were obtained earlier. For each particle the data extend beyond 75 MeV. The ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ yields approach zero, respectively, in the neighborhood of threshold energies for the ($p$, ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$), ($d$, ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$), (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$), and ($\alpha$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$) reactions. The $p$- and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-induced yields have similar energy dependences, peaking at roughly 10 MeV above threshold; in contrast, the maximum cross sections for the $d$ and $\alpha$ curves occur 30-50 MeV above threshold energies. The maximum yield from ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-induced reactions (98 mb) is about a factor of 3 larger than that for $p$, $d$, or $\alpha$. These results suggest that $\alpha$-particle pickup may be an important part of the ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ yield at the lower energy part of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ excitation function.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(d, x)$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^3{}_{}{}^{}\mathrm{He}, x)$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\alpha , x)$; $E\sim 20-80$ MeV; measured $\sigma \mathrm{}\left(E\right)\mathrm{}$; Ge(Li) detector. Deduced reaction mechanism.

• Received 4 September 1974

DOI:https://doi.org/10.1103/PhysRevC.11.50