Raman line shapes in liquid CH3I and CD3I

Abstract

The six fundamental bands of CH3I and CD3I, both as pure liquids and in solution with CS2, have been studied in order to obtain information about the molecular rotational and vibrational dynamics. Emphasis was placed on the features of the spectra that can be interpreted independent of a particular model. An examination for Boltzmann asymmetry in the A1 and E bands indicates that the former, being symmetric, are amenable to classical description, while the latter, being asymmetric, definitely require quantum mechanical interpretations. With respect to the validity of the assumption that rotation-vibration coupling can be ignored, we give evidence of substantial coupling effects in a nondegenerate A1 mode (v1) as well as in the doubly degenerate E modes. We emphasize that, in attempting to obtain dynamical information, several bands of any given liquid must be studied and compared in order to decide which can be used with confidence in a detailed analysis. The consistency of the rotational diffusion model for describing the tumbling motion of the methyl iodide molecules has been confirmed.

Dynamics of confined methyl iodide studied by Raman spectroscopy

“…1 16,21 On performing isotopic dilution experiments, a narrowing of the C-I stretching band of methyl iodide was found, giving a linewidth of about 88% relative to undiluted methyl iodide. The half-width at half-height of this band is given by 1/ vib .…”

“…16,18 Thus, the normalized anisotropic correlation function can be written as a product of the vibrational and the reorientational correlation function: In the case of the 3 mode of methyl iodide, the vibrational and the reorientational relaxation are believed to be uncoupled.…”

Estudo da dinâmica de líquidos iônicos por espectroscopia Raman

“…A fim de confirmar a confiabilidade da forma de linha dada pelo equipamento Jobin-Yvon T64000, foi feita a comparação da banda obtida nesse equipamento com a registrada no equipamento Jobin-Yvon U1000 duplo monocromador em que o sistema de detecção é uma fotomultiplicadora (Figura 10.a). A bandaanalisada foi a banda ν 1 do estiramento C-I do iodometano que possui um extenso estudo na literatura de sua forma de linha[35][36][37] . Os espectros do iodometano foram obtidos utilizando como radiação incidente a linha em 514,5 nm do Ar + .…”