Photoprotons from Cobalt

Abstract

The charged particles ejected from a thin cobalt foil by the bremsstrahlung x-rays from a 24-Mev betatron have been observed in nuclear emulsions. Yields measured in units of ${10}^4$ particles per mole per roentgen unit are: protons, 49±10; deuterons, less than 1; alpha particles 1.6±0.5 (corrected for absorption in cobalt foil). The angular distribution of the photoprotons could be fitted with a curve of the shape of $I\left(\theta \right)=71+8\mathrm{}{(sin\theta +sin\theta cos\theta )}^2$. The photoproton energy distribution can be accounted for mainly by evaporation from a compound nucleus, although 5 or 10 percent could be from a direct process. The relative absence of photodeuterons in cobalt, compared with the case of copper which has similar binding energies, suggests that the shell structure may be important in allowing photodeuteron emission.