Precision ground state mass of 12Be and an isobaric multiplet mass equation (IMME) extrapolation for 2+ and 02+ states in the T=2, A=12 multiplet

摘要

We report the mass measurement of the short-lived 12Be nuclide (T1/2=21.5 ms) performed using the Penning trap mass spectrometer TITAN at TRIUMF. Our mass excess value of 25 078.0(2.1) keV is in agreement with previous measurements, but is a factor of 7 more precise than the Atomic Mass Evaluation of 2003. To address an unresolved discussion on the spin assignment of isospin T=2 states in 12C and 12O, we reevaluate the isobaric mass multiplet equation for the lowest lying T=2 multiplet in the A=12 system and use the extracted parameters to extrapolate from the known excited 2+ and 0+ states in 12Be. Though this analysis favors the second known T=2 state in 12C to be 2+, 0+ cannot be excluded.