OBSERVATION OF DELAYED PROTON RADIOACTIVITY

The observation of delayed proton emission is reported. Bombardment of both aluminum and silicon with 97-Mev protons leads to the emission of delayed proton energy groups from 2 to 5 Mev. They follow the beta decay of Si25 (T1/2 about 0.3 sec) to proton-unstable excited states of Al25. Delayed protons were also observed following bombardment of Mg, Na, F, N, and O. The energy groups in the delayed proton spectra are explained by assuming that, in each case, a nuclide whose (Z, N) is of the form (2k + 2, 2k − 1) is the parent nuclide, the decay chain being of the form:[Formula: see text]The observed delayed proton energies are those deduced by assuming that known levels of the intermediate nucleus emit the protons. Agreement of this kind, together with cross bombardment, threshold, and lifetime measurements, established the observation of the previously unreported Si25. With less experimental detail, delayed protons have been assigned to the decay schemes of the previously unreported Mg21, Ne17, and O13.