Emission is observed from six manifolds of Er in the tungstates at 77°K. Their signatures and intrinsic lifetimes in microseconds are: Er2H9/2, <5; Er4S3/2, 25; Er4F9/2, ∼5; Er4I9/2, ∼13; Er4I11/2, 120; and Er4I13/2, ∼4500. A seventh manifold (Er2H11/2) emits when thermally populated from Er4S3/2 at 295°K. The principal transitions from all of these manifolds are to the ground manifold (Er4I15/2); as a result, radiation reabsorption is strong for each manifold and random migration of excitation between Er4I13/2 manifolds is possible at low Er concentrations. Further, due to the small spacings between the various manifolds of Er, relaxation by internal conversion processes is prevalent. Taking these factors and self-quenching interactions of Tb5D3 and Er into account, the nonradiative transfer of energy from Tb5D3 or Tb5D4 to Er, from Er2H11/2, Er4S3/2, Er4I9/2, Er4I11/2, or Er4I13/2 to Tb, and the equivalent self-quenching interactions of Er are all indicated to be by dipole—dipole in character.