Two-quasiparticle states in ¹⁶⁶Er have been studied using the ¹⁶⁷Er(d,t) ¹⁶⁶Er, ¹⁶⁷Er(³He,α) ¹⁶⁶Er, ¹⁶⁵Ho(³He,d) ¹⁶⁶Er, and ¹⁶⁵Ho(α,t) ¹⁶⁶Er reactions. Beams of 15 MeV deuterons, 24 MeV ³He⁺⁺, and 27 MeV α particles were produced by the McMaster University model FN tandem Van de Graaff accelerator. The reaction products were analyzed with an Enge split-pole magnetic spectrograph and detected with photographic emulsions. Angular distributions were obtained for the (d,t) and (³He,d) reactions at twelve and ten angles, respectively. The data were fitted with a peak finding program to yield peak energies and cross sections up to ~ 2700 keV in excitation energy, although selected peaks were investigated at somewhat higher energies.
The interpretation of the data was performed within the framework of the Unified model, incorporating pairing effects. In the neutron transfer study, two-quasiparticle states formed by removing a particle from the predominantly 7/2⁺ ¹⁶⁷Er ground state were investigated, while the proton transfer study dealt with two-quasiparticle states formed by adding a particle to the 7/2⁻ ground state of ¹⁶⁵Ho. Several previous assignments have been supported while many new ones are suggested or proposed. In contrast, several other assignments proposed in an earlier proton transfer study have been refuted.
Earlier observations that several states were populated in both the neutron transfer and proton transfer reactions have been confirmed and extended. In addition, the observation in the (d,t) reaction of several states populated by ℓ=0 neutron transfers has been interpreted in terms of a complex mixing scheme involving the 7/2⁺±1/2⁺ configurations.