Recoil Studies of Reactions of Indium with Medium Energy Protons and Alpha Particles

Recoil ranges projected along the beam direction have been measured for the ($\alpha , \alpha \gamma$), ($\alpha , \alpha n$), ($\alpha , \mathrm{pn}$), and ($p, p\gamma$) reactions on ${\mathrm{In}}^{115}$ and for the ${\mathrm{In}}^{113}(p, n)$ reaction, with 5 to 10 MeV protons and 20 to 40 MeV alpha particles. The results have been compared with values expected for compound-nucleus formation and reasonable agreement is obtained for the ($\alpha , \mathrm{pn}$), ($p, p\gamma$), and ($p, n$) reactions. The measured range for the ($\alpha , \alpha n$) reaction agrees with calculation at the lowest energy studied but is somewhat low at the highest bombarding energy. In the case of the ($\alpha , \alpha \gamma$) reaction the measured ranges are a factor of 3 to 6 smaller than the calculated values, indicating a direct interaction process. The recoil ranges expected for Coulomb excitation have been computed for the ($\alpha , \alpha \gamma$) and ($p, p\gamma$) reactions and are substantially smaller than the experimental values. Excitation function measurements for the ($\alpha , \mathrm{pn}$) reaction are also presented.