The spin-forbidden spectrum of Fe²⁺in silicate garnets

Abstract

A strong-field coupling scheme of 'once-diagonalisation' is proposed to calculate the spin-forbidden bands of the Fe2+ ions located in the D2 symmetrical eightfold site in silicate garnet. The method is to establish the energy matrices of the strong-field terms of the D2 point group of the d4(d6) electron configuration directly, so as to diagonalise simultaneously the crystal field (as a whole) and the electrostatic repulsion energy between the electrons. According to this scheme, making use of the observed data of the spin-allowed spectrum, the authors have, using only one adjustable parameter B (with C=4B), obtained all the spin-forbidden bands. Their results are in quite good agreement with the twenty bands observed. As to the spin-allowed spectrum, the assignment of Newman et al. (1978) is used in their calculations and supported by their theoretical results.