Figure 2
Energy eigenvalues of Ho for states with LZ=0.
At λ = 0 the singlets have E = 3J/4 and the triplets have E = −J/4. For λ > 0 the labels “singlet” and “triplet” are no longer strictly defined (in their usual sense) nevertheless the relatively small energy shifts suggest that these labels retain some meaning, this claim is supported by directly examining the character of the eigenstates. It is interesting to note that, already in the octahedral problem, the lowest energy (non-degenerate) state has no singlet contribution to its wavefunction for any value of λ, thus radiative transitions from this state are forbidden.
