Previously unknown isotopes30 Ar and 29 Cl have been identified by measurement of the trajectories of their in-flight decay products 28 S þ p þ p and 28 S þ p, respectively. The analysis of angular correlations of the fragments provided information on decay energies and the structure of the parent states. The ground states of 30 Ar and 29 Cl were found at 2.25 þ0.15 −0.10 and 1.8 AE 0.1 MeV above the two-and one-proton thresholds, respectively. The lowest states in 30 Ar and 29 Cl point to a violation of isobaric symmetry in the structure of these unbound nuclei. The two-proton decay has been identified in a transition region between simultaneous two-proton and sequential proton emissions from the 30 Ar ground state, which is characterized by an interplay of three-body and two-body decay mechanisms. The first hint of a fine structure of the two-proton decay of 30 Ar à ð2 þ Þ has been obtained by detecting two decay branches into the ground and first-excited states of the 28 S fragment.