  We apply Coupled Cluster Method to a strongly correlated lattice and develop
the Spectral Coupled Cluster equations by finding an approximation to the
resolvent operator, that gives the spectral response for an certain class of
probe operators. We apply the method to a $MnO_2$ plane model with a parameters
choice which corresponds to previous experimental works and which gives a
non-nominal symmetry ground state.
  We show that this state can be observed using our Spectral Coupled Cluster
Method by probing the Coupled Cluster solution obtained from the nominal
reference state. In this case one observes a negative energy resonance which
corresponds to the true ground state.
