Study of exchange-coupled pairs of Cr³⁺ ions in Rb₃Cr₂Cl₉

Abstract

The spectrum of Cr³⁺ pairs in Rb₃Cr₂Cl₉ has been studied using high resolution optical absorption and Zeeman spectroscopy in magnetic fields up to 13 T. In particular, a detailed investigation of transitions from the pair ground manifold (⁴ A ₂×⁴ A ₂) to the singly-excited pair manifold (⁴ A ₂ײ T ₁) has been made and the results are discussed in terms of a recent new theoretical approach to the problem of pairs of D_3h symmetry. The vibronic spectrum associated with the pair transitions to the (⁴ A ₂ײ T ₁) manifold has also been measured and it is shown that it may be explained in terms of strong spinphonon coupling to a small number of A_1g modes.