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

TL;DR

This study investigates proton-unstable argon and chlorine isotopes using decay-in-flight measurements, discovering new isotopes and states, and analyzing their separation energies with cluster models to extend understanding beyond the proton dripline.

Contribution

First observation of ground states of $^{30}$Cl and $^{28}$Cl isotopes, and excited states of $^{31}$Ar and $^{29}$Ar, with systematic analysis of their proton separation energies using cluster models.

Findings

Discovered $^{30}$Cl and $^{28}$Cl ground states.

Measured $2p$-separation energy of $^{31}$Ar as 6(34) keV.

Identified $^{29}$Ar state with $S_{2p} = -5.50(18)$ MeV.

Abstract

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 micro-strip 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 $^{30}$Cl and $^{28}$Cl have been observed for the first time, providing the $1p$-separation energies $S_p$ of $-0.48(2)$ and $-1.60(8)$ MeV, respectively. The relevant systematics of $1p$ and $2p$ separations 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 to infer the $2p$-separation energy $S_{2p}$ of 6(34) keV for its ground state. The first-time observed state in $^{29}$Ar with $S_{2p} = -5.50(18)$ MeV can be identified either as a ground or an excited state according to different systematics.