Molecular reorientation of benzene in carbon tetrachloride, tetramethylsilane and neopentane solutions

Abstract

The depolarized Rayleigh scattering of benzene in CCl₄, C(CH₃)₄ and Si(CH₃)₄ solutions has been investigated. Despite the similar molecular sizes and polarizabilities of the solvents, the wing spectra in dilute solutions are observed to be very different. Orientational memory functions calculated from the spectra show a pronounced oscillatory pattern in the CCl₄ solutions, the pattern being much less obvious in the C(CH₃)₄ and Si(CH₃)₄ solutions. Since it is improbable that these changes are due to changes in the interaction-induced scattering, they are attributed to changes in the orientational dynamics. Following previous work on benzene, the oscillatory pattern is attributed to librational motion of the benzene molecule in the liquid. The libration persists if benzene is encaged by heavy molecules, such as CCl₄, but diminishes in solutions with light molecules, such as C(CH₃)₄ and Si(CH₃)₄.