The effect of resonant vibrational coupling on the frequency of the ν 2 mode of liquid methyl iodide in Raman scattering and infrared absorption

Abstract

The ν 2 mode of methyl iodide has been measured in isotropic and anisotropic Raman scattering, and in infrared absorption in the neat liquid and in isotopic dilution with the deuterated compound. The local field affecting the shape and position of the intense infrared profile has been taken into account by a continuum dielectric approximation. The isotopic dilution shifts observed indicate the action of resonant intermolecular vibrational coupling which presumably is caused by transition dipole interaction. The results are, in principle, in agreement with current theories. For a comparison, certain approximations are necessary (MSM, etc.), which seem to be responsible for the fact that quantitative agreement is not yet very good.