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 ${}^{30}\mathrm{Cl}$ and ${}^{28}\mathrm{Cl}$ have been observed for the first time, providing the $1p$-separation energies $S_p$ of $-0.48\left(2\right)$ and $-1.60\left(8\right)$, MeV, respectively. The relevant systematics of $1p$- and $2p$-separation energies have been studied theoretically in the $\mathrm{core}+p$ and $\mathrm{core}+p+p$ cluster models. The first-time observed excited states of ${}^{31}\mathrm{Ar}$ allow one to infer the $2p$-separation energy $S_{2p}$ of 6(34) keV for its ground state. The first-time observed state in ${}^{29}\mathrm{Ar}$ with $S_{2p}=-5.50\left(18\right)$ MeV can be identified as either a ground state or an excited state according to different systematics.

• Received 19 June 2018

DOI:https://doi.org/10.1103/PhysRevC.98.064308