Breakdown of the Isobaric Multiplet Mass Equation for theA=20and 21 Multiplets Academic Article uri icon

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abstract

  • Using the Penning trap mass spectrometer TITAN, we performed the first direct mass measurements of (20,21)Mg, isotopes that are the most proton-rich members of the A = 20 and A = 21 isospin multiplets. These measurements were possible through the use of a unique ion-guide laser ion source, a development that suppressed isobaric contamination by 6 orders of magnitude. Compared to the latest atomic mass evaluation, we find that the mass of (21)Mg is in good agreement but that the mass of (20)Mg deviates by 3 σ. These measurements reduce the uncertainties in the masses of (20,21)Mg by 15 and 22 times, respectively, resulting in a significant departure from the expected behavior of the isobaric multiplet mass equation in both the A = 20 and A = 21 multiplets. This presents a challenge to shell model calculations using either the isospin nonconserving universal sd USDA and USDB Hamiltonians or isospin nonconserving interactions based on chiral two- and three-nucleon forces.

authors

  • Gallant, AT
  • Brodeur, M
  • Andreoiu, C
  • Bader, A
  • Chaudhuri, A
  • Chowdhury, U
  • Grossheim, A
  • Klawitter, R
  • Kwiatkowski, AA
  • Leach, KG
  • Lennarz, Annika
  • Macdonald, TD
  • Schultz, BE
  • Lassen, J
  • Heggen, H
  • Raeder, S
  • Teigelhöfer, A
  • Brown, BA
  • Magilligan, A
  • Holt, JD
  • Menéndez, J
  • Simonis, J
  • Schwenk, A
  • Dilling, J

publication date

  • August 22, 2014