Breakdown of the Isobaric Multiplet Mass Equation for the A = 20 and 21 Multiplets

Abstract

Using the Penning trap mass spectrometer TITAN, we performed the first direct mass measurements of 20,21Mg, 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 six orders of magnitude. Compared to the latest atomic mass evaluation, we find that the mass of 21Mg is in good agreement but that the mass of 20Mg deviates by 3σ. These measurements reduce the uncertainties in the masses of 20,21Mg 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 non-conserving USDA/B Hamiltonians or isospin non-conserving interactions based on chiral two- and three-nucleon forces.

5 pages, 2 figures

References in corpus (5)

• Three-body forces: From cold atoms to nuclei
• New precision mass measurements of neutron-rich calcium and potassium isotopes and three-nucleon forces
• Three-body forces and proton-rich nuclei
• Evidence for a breakdown of the Isobaric Multiplet Mass Equation: A study of the A=35, T=3/2 isospin quartet
• Isobaric Multiplet Mass Equation for $A\le 71$ Revisited

Cited by in corpus (10)

• Identification of the Lowest $T=2$, $J^{\pi =}{0}^{+}$ Isobaric Analog State in ${}^{52}$Co and Its Impact on the Understanding of $\beta$-Decay Properties of ${}^{52}$Ni
• The roles of three-nucleon force and continuum coupling in mirror symmetry breaking of oxygen mass region
• Beta-decay study of $T_z=-2$ proton-rich nucleus ${}^{20}$Mg
• Observation of excited states in ${}^{20}$Mg sheds light on nuclear forces and shell evolution
• Precision mass measurements of magnesium isotopes and implications on the validity of the Isobaric Mass Multiplet Equation
• Isobaric multiplet mass equation in the $A=31$ $T=3/2$ quartets
• High-precision $Q_{EC}$-value measurement of the superallowed ${\beta }^{+}$ emitter ${}^{22}$Mg and an evaluation of the $A=22$ isobaric triplet
• Isospin Mixing and the Cubic Isobaric Multiplet Mass Equation in the Lowest T = 2, A = 32 Quintet
• Low-Background In-Trap Decay Spectroscopy with TITAN at TRIUMF
• Sensitivity Increases for the TITAN Decay Spectroscopy Program