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Projectile fragments separated in flight with the FRS have been injected into the storage ring ESR. Operating the ESR in the isochronous mode has enabled high-resolution mass measurements of short-lived isotopes. Already in our pilot experiments the Isochronous Mass Spectrometry (IMS) has provided accurate results for a restricted isotope range in the neighborhood of a selected isotope characterized by the best isochronous condition. In the present experiment this restriction has been overcome by precise external magnetic rigidity determination (1.5·10–4) at the dispersive midplane of the FRS. In this way the mass resolving power for neutron-rich fission fragments covering a large mass-over-charge ratio in one spectrum has been improved by up to one order of magnitude and the accuracy by more than a factor of two. [ABSTRACT FROM AUTHOR]

Abstract A thick neutron skin emerges from the first determination of root mean square radii of the proton distributions for 17−22N from charge changing cross section measurements around 900 A MeV at GSI. Neutron halo effects are signalled for 22N from an increase in the proton and matter radii. The radii suggest an unconventional shell gap at N = 14 arising from the attractive proton–neutron tensor interaction, in good agreement with shell model calculations. Ab initio , in-medium similarity re-normalization group, calculations with a state-of-the-art chiral nucleon–nucleon and three-nucleon interaction reproduce well the data approaching the neutron drip-line isotopes but are challenged in explaining the complete isotopic trend of the radii. [ABSTRACT FROM AUTHOR]

Previously unknown isotopes 30Ar and 29C1 have been identified by measurement of the trajectories of their in-flight decay products 28S + p + p and 28S + 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 30Ar and 29C1 were found at 2.25-0.10+0.15 and 1.8 ±0.1 MeV above the two- and one-proton thresholds, respectively. The lowest states in 30Ar and 29C1 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 30Ar 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 30Ar* (2+) has been obtained by detecting two decay branches into the ground and first-excited states of the 28S fragment. [ABSTRACT FROM AUTHOR]