Fine Structures of Photoprotons from Si²⁸

The energy spectrum of photoprotons from silicon-28 is investigated using 24 Mev bremsstrahlung. The energy loss is about 30% for 3 Mev and about 10% for 6 Mev protons. The number of detected tracks is 4366 for a scanned area of 1.6 cm². The energy spectrum is deduced by the statistical model with the level density omega given by omega = Cexp (E/2.8)Mev⁻¹. The many fine structures may be explained by a resonating group model. The cross section of Si²⁸( gamma ,p)Al²⁷ is compared with that for Al²⁷(p, gamma )Si²⁸ and the shapes coincide fairly well. (N.W.R.)