Elucidation of the anomalous A = 9 isospin quartet behaviour

Abstract

Recent high-precision mass measurements of ${}^9$Li and ${}^9$Be, performed with the TITAN Penning trap at the TRIUMF ISAC facility, are analyzed in light of state-of-the-art shell model calculations. We find an explanation for the anomalous Isobaric Mass Multiplet Equation (IMME) behaviour for the two $A$ = 9 quartets. The presence of a cubic $d$ = 6.3(17) keV term for the $J^{\pi }$ = 3/2${}^{-}$ quartet and the vanishing cubic term for the excited $J^{\pi }$ = 1/2${}^{-}$ multiplet depend upon the presence of a nearby $T$ = 1/2 state in ${}^9$B and ${}^9$Be that induces isospin mixing. This is contrary to previous hypotheses involving purely Coulomb and charge-dependent effects. $T$ = 1/2 states have been observed near the calculated energy, above the $T$ = 3/2 state. However an experimental confirmation of their $J^{\pi }$ is needed.

5 pages, 2 figures

References in corpus (8)

• First Penning-trap mass measurement in the millisecond half-life range: the exotic halo nucleus 11Li
• First direct mass-measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He
• Comparative tests of isospin-symmetry-breaking corrections to superallowed 0+-to-0+ nuclear beta decay
• Investigations of three, four, and five-particle exit channels of levels in light nuclei created using a 9C beam
• First Use of High Charge States for Mass Measurements of Short-lived Nuclides in a Penning Trap
• Verifying the accuracy of the TITAN Penning-trap mass spectrometer
• A new mass value for 7Li
• Effects of isospin mixing in the A=32 quintet

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