Precision mass measurements of rare isotopes near N=Z=33 produced by fast beam fragmentation Academic Article uri icon


  • Mass measurements of Ga63,64, Ge64,65,66, As66,67,68 and Se69 performed at the LEBIT facility at the NSCL by Penning trap mass spectrometry are presented. The rare isotopes were produced by fast beam fragmentation and in-flight separation, then converted to a low energy beam using a gas stopping technique. Masses of the N=Z nuclei As66 and Ge64 have been determined with uncertainties of δm/m=5×10-7 and 6×10-8, respectively, representing a more than ten-fold improvement in precision over previous measurements. For Ga63,64, Ge65,66, As67,68, and Se69 relative mass uncertainties of δm/ m<5×10-8 were obtained. Se69 is found to be 135 keV more bound than the value listed in the 2003 Atomic Mass Evaluation. Using theoretical Coulomb shift energies in combination with the experimental mass values for Ge65,66, As67, and Se69, masses for As65, Se66,67, and Br69 are predicted with an estimated uncertainty of 100 keV. These mass values, in conjunction with our measurements, were used to calculate improved effective lifetimes of the rp-process waiting point nuclei Ge64 and Se68. We find that Ge64 is less of a waiting point while Se68 poses a larger delay in the rp-process than previously thought. The improved mass values in this region were also used to investigate the neutron-proton pairing energy of odd-odd N=Z nuclei. © 2007 The American Physical Society.

author list (cited authors)

  • Schury, P., Bachelet, C., Block, M., Bollen, G., Davies, D. A., Facina, M., ... Sun, T.

citation count

  • 99

publication date

  • May 2007