Exchange studies in a trigonal Cr 3+ dimer system: the ( 4A 2 × 2E) and ( 4A 2 × 4A 2) states in Rb 3Cr 2Br 9

Abstract

A study of the polarised optical absorption and Zeeman spectra of Cr 2+ dimers in Rb 3Cr 2Br 9 is reported. In particular, transition between the ( 4A 2 × 4A 2) dimer ground manifold and the ( 4A 2 × 2E) singly excited manifold have been investigated, and the detailed structure of the ( 4A 2 × 2E) manifold is explained in terms of a recently proposed model for magnetic exchange in pair systems of D 3h symmetry. The ground manifold is shown to exhibit small departures from the interval rule structure, mainly due to magnetostrictive effects. Anomalously low splitting factors are found in applied magnetic field and are discussed in the context of similar effects observed in Cs 3Cr 2Br 9 but not in the chlorine isomorphs. An analysis of the vibronic structure for ( 4A 2 × 2E) is also presented.