Effects of antiferromagnetic coupling in the 5 k electronic spectra of crystals of vanadium dichloride, dibromide, and di-iodide

Abstract

Single-crystal absorption spectra at 300, 80, and 5 K of the antiferromagnetic compounds VCl₂, VBr₂, and VI₂ are reported between 5000 and 30,000 cm^–1. The energy positions and intensities of the bands are similar to those for isolated V²⁺ but spin-forbidden levels are more intense.

This intensity effect and some sharp, fine structure are explained in terms of magnetic exchange effects. A combination band due to two spin-allowed single-centre transitions is detected.