Deep excursion beyond the proton dripline. I. Argon and chlorine isotope chains

The proton-unbound argon and chlorine isotopes have been studied by measuring trajectories of their decay-in-flight products by using a tracking technique with microstrip detectors. The proton (1p) and two-proton (2p) emission processes have been detected in the measured angular correlations "heavy-fragment" +p and "heavy-fragment" +p + p, respectively. The ground states of the previously unknown isotopes Cl-30 and Cl-28 have been observed for the first time, providing the 1 p-separation energies S-p of -0.48(2) and -1.60(8), MeV, respectively. The relevant systematics of 1 p- and 2p-separation energies have been studied theoretically in the core + p and core + p + p cluster models. The first-time observed excited states of( 31)Ar allow one to infer the 2p-separation energy S-2p of 6(34) keV for its ground state. The first-time observed state in Ar-29 with S-2p = -5.50(18) MeV can be identified as either a ground state or an excited state according to different systematics.