Crossing of anisotropic and isotropic Raman components in the intermolecular resonance coupling of vibrations III-Ca(ClO4)2 and benzene solutions in acetone

Changes in the wavenumbers of the anisotropic and isotropic components of the C=O stretching band in the Raman spectrum of Ca(ClO4)2 and benzene solutions in acetone were investigated. Non‐coincidence values defined as Δv = vaniso — viso for the C = O band in Ca(ClO4)2 solutions were positive (+ 5 cm−1) for bulk acetone and negative (—25 cm−1) for acetone‐shared ion pairs. In acetone solutions diluted with benzene there is a decrease in C = O non‐coincidence from +5 cm−1 down to about — 1 cm−1. The change of non‐coincidence sign appears at a benzene/acetone molar ratio of 10. The concept of third‐body mediation is applied to explain the observed changes of non‐coincidence in highly polar and non‐polar diluents.