Observation of two-proton radioactivity of (19)Mg by tracking the decay products

We have observed the two-proton radioactivity of the previously unknown 19Mg ground-state by tracking the decay products in-°ight. For the ¯rst time, the trajectories of the 2p-decay products, 17Ne+p+p, have been measured by using tracking micro-strip detectors which allowed to reconstruct the 2p-decay vertices and fragment correlations. The half-life of 19Mg deduced from the measured vertex distribution is 4.0(15) ps in the system of 19Mg. The Q-value of the 2p-decay of the 19Mg ground-state inferred from the measured p{p{17Ne correlations is 0.75(5) MeV.