Energy levels and lifetimes of Gd IV and enhancement of the electron electric dipole moment

We have calculated energy levels and lifetimes of 4f⁷ and 4f⁶5d configurations of Gd IV using Hartree-Fock and configuration-interaction methods. This allows us to reduce significantly the uncertainty of the theoretical determination of the electron electric dipole moment (EDM) enhancement factor in this ion and, correspondingly, in gadolinium-containing garnets for which such measurements were recently proposed. Our new value for the EDM enhancement factor of Gd³⁺ is -2.2±0.5. Calculations of energy levels and lifetimes for Eu III are used to control the accuracy.