On the masses of A=54 isospin septet and the isobaric multiplet mass equation

Using the ground-state mass of ^(52)Ni and two-proton decay energy of ^(54)Zn,the ground-state mass excess of ^(54)Zn is deduced to be-6504(85)keV.This value is about 2 MeV lower than the prediction of the quadratic form of the isobaric multiplet mass equation(IMME).A cubic fit to the existing mass data of the A=54,T=3 isospin multiplet yields a surprisingly large d coefficient of IMME,i.e.,d=18.6(27),being 6.9σdeviated from zero,and the resultant|b/c|ratio significantly deviates from the systematics.This phenomenon is analyzed in this study,and we conclude that the breakdown of the quadratic form of IMME could be likely due to the mis-assignment of the T=3 isobaric analog state(IAS)in the T_(Z)=1 nucleus ^(54)Fe or extremely strong isospin mixing.