Reorientation of mesitylene in the neat liquid has been investigated using a combination of IR and Raman techniques.Assuming that the vibrational contribution to line broadening is the same for the IR and Raman spectra and that the rotational diffusion model is a good description for the reorientation of this molecule, rotational diffusion constants have been determined experimentally. The temperature dependences of both the tumbling and the spinning of mesitylene are explained on the basis of the hydrodynamic models for reorientational motion.

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