Diproton decay of nuclei on the proton drip line.

The process of direct two-proton decay of nuclei with Z 22-28 on the proton drip line is considered. On the basis of new Od3t2 Offi2 -shell-model mass extrapolations, '9Ti, 42Cr, 45Fe, Ni, and Ni are found to be bound to single-proton decay but unbound to two-proton decay. New estimates of the spectroscopic factors and lifetimes have been made. The decays of Ti, Fe, and Ni are found to be promising for further experimental investigation.