  Candidates for three excited states in the 66^Se have been identified using
the recoil-{\beta} tagging method together with a veto detector for
charged-particle evaporation channels. These results allow a comparison of
mirror and triplet energy differences between analogue states across the A = 66
triplet as a function of angular momentum. The extracted triplet energy
differences follow the negative trend observed in the f_7/2 shell. Shell-model
calculations indicate a continued need for an additional isospin non-conserving
interaction in addition to the Coulomb isotensor part as a function of mass.
