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 (1 p ) and two-proton (2 p ) 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 ³⁰Cl and ²⁸Cl 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 2 p -separation energies have been studied theoretically in the core +p and core +p +p cluster models. The first-time observed excited states of ³¹Ar allow one to infer the 2 p -separation energy S_{2 p} of 6(34) keV for its ground state. The first-time observed state in ²⁹Ar with S_{2 p}=-5.50 (18 ) MeV can be identified as either a ground state or an excited state according to different systematics.