Masses of the radionuclides ${}^{32,33}\mathrm{Si}$ and ${}^{34}\mathrm{P}$ and of the stable nuclides ${}^{32}\mathrm{S}$ and ${}^{31}\mathrm{P}$ have been measured with the Low Energy Beam and Ion Trap (LEBIT) Penning trap mass spectrometer. Relative mass uncertainties as low as $3\times {10}^{-9}$ have been achieved. The measured mass value of ${}^{32}\mathrm{Si}$ differs from the literature value by four standard deviations. The precise mass determination of ${}^{32}\mathrm{Si}$ and ${}^{32}\mathrm{S}$ have been employed to test the validity of the quadratic form of the isobaric multiplet mass equation (IMME) for the most well known $A=32$, $T=2$ isospin quintet. The new experimental results indicate a dramatic breakdown of the model.

• Received 31 July 2009

DOI:https://doi.org/10.1103/PhysRevC.80.051302