The weak field representation of the crystal field matrices of d^4,6 ions and the electronic absorption spectrum of RbFeF₃

Abstract

The electronic absorption spectrum of RbFeF₃ is reported and analysed by means of crystal field theory. It is shown that the strong field formalism is limited for high spin Fe²⁺ and the weak field representation should be used to interpret the many triplet states. Published spin-orbit weak field matrices for d^4,6 are shown to contain errors. The weak field matrices in the absence of spin-orbit coupling have been derived and they are used to assign the spectrum of RbFeF₃.