Theoretical analysis and intensity calculation for the f → d absorption spectrum of U³⁺ in the LiY F₄ crystal

The absorption spectrum of U³⁺ in LiY F₄ has been well calculated using the model proposed by Reid for calculations of spectra. The relevant formulae for the matrix element calculations which were omitted in this model are now described in detail, and the values of the direct and exchange coefficients associated with the f–d Coulomb interactions within the f²d configuration are derived and listed. The amount of reduction for the f–d Coulomb interaction parameters from the free-ion values is found to be , which is much larger than the value of 26% for the isoelectronic Nd³⁺ lanthanide ion in the same host.