A. Blazhev

Proton-proton correlations observed in two-proton radioactivity of 94Ag.

The stability and spontaneous decay of naturally occurring atomic nuclei have been much studied ever since Becquerel discovered natural radioactivity in 1896. In 1960, proton-rich nuclei with an odd or an even atomic number Z were predicted to decay through one- and two-proton radioactivity, respectively. The experimental observation of one-proton radioactivity was first reported in 1982, and two-proton radioactivity has now also been detected by experimentally studying the decay properties of 45Fe (refs 3, 4) and 54Zn (ref. 5). Here we report proton–proton correlations observed during the radioactive decay of a spinning long-lived state of the lightest known isotope of silver, 94Ag, which is known to undergo one-proton decay. We infer from these correlations that the long-lived state must also decay through simultaneous two-proton emission, making 94Ag the first nucleus to exhibit one- as well as two-proton radioactivity. We attribute the two-proton emission behaviour and the unexpectedly large probability for this decay mechanism to a very large deformation of the parent nucleus into a prolate (cigar-like) shape, which facilitates emission of protons either from the same or from opposite ends of the ‘cigar’.

Recent developments at the ISOL facility of GSI Darmstadt

The research programme pursued at the ISOL facility of GSI Darmstadt focuses on the study of decay properties of nuclei along the N≅Z line between the double shell closures at 56Ni and 100Sn. In this report, the major scientific achievements obtained in the past two years are reviewed, with particular emphasis being put on the detection techniques.

Recent results from β‐decay studies in the 100Sn region

The decays of the neutron deficient nuclei 94,95Ag, 100,102In and 102Sn were investigated at the GSI on‐line mass separator. The Gamow‐Teller decay of 100,102In and 102Sn was studied by using an array of germanium detectors and a total absorption spectrometer. In 94Ag and 95Ag, spin‐gap isomers were identified and their decays were investigated. Results obtained in these studies are discussed and compared to predictions of shell model calculations.