First direct mass measurements of stored neutron-rich 129,130,131Cd isotopes with FRS-ESR

A 410 MeV/u 238U projectile beam was used to create cadmium isotopes via abrasion-fission in a beryllium target placed at the entrance of the in-flight separator FRS at GSI. The fission fragments were separated by the FRS and injected into the isochronous storage ring ESR for mass measurements. Isochronous Mass Spectrometry (IMS) was performed under two different experimental conditions, with and without B\u3c1-tagging at the high-resolution central focal plane of the FRS. In the experiment with B\u3c1-tagging the magnetic rigidity of the injected fragments was determined with an accuracy of 2 c510-4. A new method of data analysis, which uses a correlation matrix for the combined data set from both experiments, has provided experimental mass values of 25 rare isotopes for the first time. The high sensitivity and selectivity of the method have given access to nuclides detected with a rate of a few atoms per week. In this letter we present for the 129,130,131Cd isotopes mass values directly measured for the first time. The experimental mass values of cadmium as well as for tellurium and tin isotopes show a pronounced shell effect towards and at N=82. Shell quenching cannot be deduced from a single new mass value, nor by a better agreement with a theoretical model which explicitly takes into account a quenching feature. This is in agreement with the conclusion from \u3b3-ray spectroscopy and confirms modern shell-model calculations

New Developments for Isochronous Mass Measurements of Short-Lived Nuclei

The combination of the in\u2010flight separator FRS and the storage\u2010ring ESR at GSI offers unique possibilities for high accuracy mass and lifetime measurements of bare and few\u2010electron fragments. Operating the ESR in the isochronous mode allows for measurements of revolution frequencies of stored ions without cooling. Isochronous Mass Spectrometry (IMS) can be applied to fragments with half\u2010lives as short as several tens of microseconds. Newly developed magnetic rigidity tagging increases the resolving power of IMS to about 500000. IMS can be used to measure masses of nuclei with rates even lower than one ion per day, a property also needed for the purpose of the ILIMA project at the future facility FAIR

Half-life measurement of stored fully ionized and hydrogen-like 122I ions

The half-lives of fully ionized and hydrogen-like (H-like) 122I ions have been measured in a heavy-ion storage ring. The \u3b2+-decay constants for both charge states and the electron capture (EC) decay constant of H-like ions have been determined. The EC-decay constant in H-like 122I ions \u3bbH-like EC = 7.35(33) \ub7 10 124 s 121 is, within the uncertainty, the same as the one in neutral atoms. This result is in agreement with the estimates of recent theoretical considerations on the EC-decay of few-electron ions that explicitly take into account the conservation of the total angular momentum of the nucleus plus lepton(s) system and its projections. No firm confirmation could be concluded from our results on the predicted effect that allowed Gamow-Teller transitions become forbidden if the initial and final total angular momenta are not equal

Ground-state configuration of neutron-rich Aluminum isotopes through Coulomb breakup

Neutron-rich 34,35Al isotopes have been studied through Coulomb excitation using LAND-FRS setup at GSI, Darmstadt. The method of invariant mass analysis has been used to reconstruct the excitation energy of the nucleus prior to decay. Comparison of experimental CD cross-section with direct breakup model calculation with neutron in p3/2 orbital favours 34Al(g.s) - νp3/2 as ground state configuration of 35Al. But ground state configuration of 34Al is complicated as evident from γ-ray spectra of 33Al after Coulomb breakup of 34Al. \ua9 Owned by the authors, published by EDP Sciences, 2014