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

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 Sp of −0.48(2) and −1.60(8) MeV, respectively. The relevant systematics of 1p 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 to infer the 2p-separation energy S2p of 6(34) keV for its ground state. The first-time observed state in 29 Ar with S2p = −5.50(18) MeV can be identified either as a ground or an excited state according to different systematics. * D.Kostyleva@gsi.de ary states in many theoretical applications. This naturally leads us to the question: what are the limits of nuclear structure existence? In other words, how far beyond the driplines the nuclear structure phenomena fade and are completely replaced by the continuum dynamics? This question represents a motivation for studies of nuclear systems far beyond the driplines.The proton and neutron driplines have been accessed for nuclides in broad ranges of Z (number of protons) and N (number of neutrons) of the nuclear chart. However, even in these regions the information about the nearest to the dripline unbound isotopes is scarce and often miss-

2018 update of the discoveries of nuclides

“…I. Argon and chlorine isotope chains". 16 A 885 A·MeV 36 Ar beam from the SIS-FRS facility at GSI was used to produce a 620 MeV A·MeV 31 Ar beam in the first half of the FRS set in a separator-spectrometer mode. Unbound reaction products were generated at the 9 Be secondary target located at the FRS middle focal plane.…”

Towards the Limits of Existence of Nuclear Structure: Observation and First Spectroscopy of the Isotope K31 by Measuring Its Three-Proton Decay

“…In this work we continue the "excursion beyond the proton dripline" of Ref. [1] by presenting the results of additional analysis of the data obtained with a 31 Ar secondary beam [8]. In the experiment, described in detail in Refs.…”

“…In recent experimental [1] and theoretical [2] studies of the lightest isotopes in the argon and chlorine isotope chains, limits of existence of the corresponding nuclear structure were addressed. For the issue of existence of nuclear structure, we adopt the approach used in Ref.…”

“…In the cases addressed in Refs. [1,8], the 29,30 Ar nuclei were produced via neutron knockout reactions from the 31 Ar ions. The decay products of unbound 29,30 Ar nuclei were tracked by a double-sided silicon micro-strip detector (DSSD) array placed just downstream of the secondary target.…”

Spectroscopy of excited states of unbound nuclei Ar30 and Cl29

“…In the case of 19 Mg, whose half-life was predicted in the range from a few ps to a few ns [8], a technique based on particle tracking of decays in flight (see details in Ref. [9]) was applied in order to investigate its decay properties. In this experiment, the trajectories of 2p decay products of 19 Mg were measured by doublesided silicon micro-strip detectors.…”