Studies of the optical spectrum band positions and spin-Hamiltonian parameters for Pa4+ ion in ThX4 (X=Cl, Br) crystals

The optical spectrum band positions and spin-Hamiltonian (SH) parameters (g factors g∥ and g⊥ and hyperfine structure constants A∥ and A⊥) for 5f1 ion Pa4+ at the tetragonal Th4+ site of ThX4 (X=Cl, Br) crystals are calculated from a complete diagonalization (of energy matrix) method (CDM). In the CDM, the magnetic (or Zeeman) interaction and hyperfine interaction terms are added to the Hamiltonian in the conventional CDM and so the optical and EPR spectra data can be studied in a unified way. The calculated results are in reasonable agreement with experimental values. The possible misprints or small errors in the experimental g factors for Pa4+ in ThX4 crystals are pointed out. The results are discussed.