D. Lunney

Penning-trap mass spectrometry of highly charged, neutron-rich Rb and Sr isotopes in the vicinity of A≈100

The neutron-rich mass region around A � 100 presents challenges for modeling the astrophysical r-process because of rapid shape transitions. We report on mass measurements using the TITAN Penning trap at TRIUMF-ISAC to attain more reliable theoretical predictions of r-process nucleosynthesis paths in this region. A new approach using highly charged (q = 15+) ions has been applied which considerably saves measurement time and preserves accuracy. New mass measurements of neutron-rich 94,97,98 Rb and 94,97 99 Sr have uncertainties of less than 4 keV and show deviations of up to 11� to previous measurements. An analysis using a parameterized r-process model is performed and shows that mass uncertainties for the A = 90 abundance region are eliminated.

Recent Results on Ne and Mg from the MISTRAL Mass Measurement Program at ISOLDE

D. Lunney a; C. Monsanglant a G. Audi a G. Bollen b; C. Borcea b;c H. Doubre a C. Gaulard a S. Henry a M. de Saint Simon a C. Thibault a C. Toader a;c N. Vieira a and the ISOLDE Collaboration b a Centre de Spectrom etrie Nucl eaire et de Spectrom etrie de Masse (CSNSM) IN2P3-CNRS, Universit e de Paris Sud, Bât. 108, F-91405 Orsay, France b CERN, CH-1211, Geneva, Switzerland c INPE, Bucharest-Magurele, Romania

Mass measurements of 56?57Cr and the question of shell reincarnation at N = 32

Binding energies determined with high accuracy provide smooth derivatives of the mass surface for analysis of shell and pairing effects. Measurements with the Penning trap mass spectrometer ISOLTRAP at CERN-ISOLDE were made for 56−57Cr for which an accuracy of 4 × 10−8 was achieved. Analysis of the mass surface for the supposed new N = 32 shell closure rather indicates a sub-shell closure, but of a different nature than known cases such as 94Sr.

Neutron Drip-Line Topography

The development of microscopic mass models is a crucial ingredient for the understanding of how most of the elements of our world were fabricated. Confidence in drip‐line predictions of such models requires their comparison with new mass data for nuclides far from stability. We combine theory and experiment using results that are state of the art: the latest mass measurements from the Penning‐trap spectrometer ISOLTRAP at CERN‐ISOLDE are used to confront the predictions of the latest Skyrme‐Hartree‐Fock‐Bogoliubov (HFB) microscopic mass models. In addition, we compare the new data to predictions of other types of mass models and the extrapolative behavior of the various models is analyzed to highlight topographical trends along the shores of the nuclear chart.