When accelerated protons, deuterons, and alpha-particles of the order of 100-Mev energy strike thin aluminum foils (0.25-0.5 mil), sizable percentages of the ${\mathrm{Na}}^{24}$ formed are ejected by the recoil process. In the higher energy range the percentage of ${\mathrm{Na}}^{24}$ ejected from the foil decreases with increase in energy of the incident particle. This behavior is first shown semiquantitatively to be a consequence of constant nuclear excitation in contrast to compound nucleus formation. Calculations are made for the expected loss of ${\mathrm{Na}}^{24}$ assuming compound nucleus formation along with randomly distributed ejection of particles in the production of ${\mathrm{Na}}^{24}$, and the agreement is found satisfactory for 70-Mev protons and 80-Mev alpha-particles but not for higher energies. Calculations are also made for the case of constant nuclear excitation with the incident particle of degraded energy leaving in the forward direction, and satisfactory agreement with the experimental values are found here over the entire energy range studied.

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