No abstract

Previously unknown isotopes30 Ar and 29 Cl have been identified by measurement of the trajectories of their in-flight decay products 28 S þ p þ p and 28 S þ p, respectively. The analysis of angular correlations of the fragments provided information on decay energies and the structure of the parent states. The ground states of 30 Ar and 29 Cl were found at 2.25 þ0.15 −0.10 and 1.8 AE 0.1 MeV above the two-and one-proton thresholds, respectively. The lowest states in 30 Ar and 29 Cl point to a violation of isobaric symmetry in the structure of these unbound nuclei. The two-proton decay has been identified in a transition region between simultaneous two-proton and sequential proton emissions from the 30 Ar ground state, which is characterized by an interplay of three-body and two-body decay mechanisms. The first hint of a fine structure of the two-proton decay of 30 Ar à ð2 þ Þ has been obtained by detecting two decay branches into the ground and first-excited states of the 28 S fragment.

appear in the even-proton number (Z) isotopes beyond the proton drip-line, in which one-proton (1p) emission is energetically prohibited but the ejection of two protons is energetically allowed due to the pairing interaction. More than 40 years after its prediction, ground-state 2p radioactivity was discovered in 2002 [2,3]. Two experiments independently observed that the ground state (g.s.) of 45 Fe decays by simultaneous emission of two protons. Later 54 Zn [4], 19 Mg [5], 48 Ni [6], and 67 Kr [7] were found to be other g.s. 2p radioactive nuclei. Among the g.s. 2p emitters hitherto observed, the halflives of 45 Fe, 48 Ni, and 54 Zn are in the range of several ms,

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-

No abstract

A multi-particle decay experiment was successfully performed at the ISOLDE Decay Station. In this new permanent station, devoted to β-decay studies, the novel MAGISOL Si-Plugin Chamber was installed to study the exotic decay modes of the proton drip-line nucleus 31 Ar. The motivation was to search for β3p and β3pγ channels, as well as to provide information on resonances in 30 S and 29 P relevant for the astrophysical rp-process. Description of the experimental set-up and preliminary results are presented.

Abstract. The N = 28 isotone60 Ge, Tz = −2, was produced and selected among the products of the fragmentation reaction of a 78 Kr beam at 150 MeV/nucleon and a Be target by means of the A1900 fragment separator at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). Its decay was studied for the first time using the optical time projection chamber. The β-decay of 60 Ge was found to be dominated by β-delayed proton emission, with a branching of ≈ 100% and half-life T 1/2 = 20 +7 −5 ms.

Prospects of experimental studies of argon and chlorine isotopes located far beyond the proton dripline are studied by using systematics and cluster models. The deviations from the widespread systematics observed in 28,29 Cl and 29,30 Ar have been theoretically substantiated, and analogous deviations predicted for the lighter chlorine and argon isotopes. The limits of nuclear structure existence are predicted for Ar and Cl isotopic chains, with 26 Ar and 25 Cl found to be the lightest sufficiently long-living nuclear systems. By simultaneous measurements of protons and γ-rays following decays of such systems as well as their β-delayed emission, an interesting synergy effect may be achieved, which is demonstrated by the example of 30 Cl and 31 Ar ground state studies. Such synergy effect may be provided by the new EXPERT setup (EXotic Particle Emission and Radioactivity by Tracking), being operated inside the fragment separator and spectrometer facility at GSI, Darmstadt.