Abstract
The ground state two-proton decay lifetime of Mg19, populated by the one-neutron knockout of an intermediate-energy Mg20 radioactive beam, was measured utilizing a new experimental technique. A thin silicon detector positioned at varying distances (0.0–1.0 mm) downstream of the reaction target measured the energy loss of Mg19 and the two-proton decay product Ne17. The lifetime was deduced from fits to the measured energy-loss line shapes and depended upon the contribution of prompt reaction processes to the yield of Ne17. For relative Ne17 prompt contributions from 82% to 92%, the extracted lifetimes ranged from 1.75+0.43−0.42 to 6.4+2.4−2.7 ps. The results are consistent with the previously reported Mg19 lifetime measurement and serve as both an important complementary study and a validation of this new technique, which can provide lifetime information for short-lived states beyond the proton drip line.