Dependence of interconfiguration excitation energies on local environment, composition and temperature in EuA 2-xB x compounds

The dependence of the energy released by removing an electron from the 4ƒ level to the conduction band on environment, composition and temperature was deduced from Mossbauer measurements on Eu A_{2- x}B_x compounds ( A = Rh or Ir, B = Pt or Al). For each system, this energy is equal to α + β x - λ m + T, where α, β and λ are constants. m is the number of B neighbors of an Eu ion. The sizes of the unit cells are consistent with the recoilless absorption data.