Theory of two-proton radioactivity with application to Mg-19 and Ni-48

We study the emission of two protons from nuclei when this is the only deca y channel. A three-body model is developed. We compare the "diproton" model with the three-body calculations. We present exploratory studies of the Mg -19 and Ni-48 ground states, which are good candidates for two-proton radio activity. The two-proton width for the Ne-17 3/2(-) state is also estimated . Our calculations give substantially lower values for the width than predi cted by the diproton model, but larger than from direct decay to the contin uum.