Rotational motions of solute molecules in supercooled and glassy media were investigated with the temperaturehyphen;dependent ESR spectra of the organic nitroxides and chlorine dioxide in some organic solvents. The rotational correlation times (tgr;Rrsquo;s) of the solutes were estimated by the method of Freedet al.for the nitroxides and by the spectral simulations based on the stochastic Liouville method for chlorine dioxide. From comparison between tgr;Rrsquo;s of the solutes and the dielectric relation times of the solvents or some equations which provide tgr;Rrsquo;s of molecules in supercooled liquid, it was concluded that a solute molecule rotates almost independently from motions of solvent molecules. The solventhyphen;dependent parts of tgr;Rrsquo;s of the solute molecules obtained in the various combinations of the solute and solvents can be treated as perturbation for the rotational motion of a solute molecule. Nonlinear dependence of tgr;Rrsquo;s of the solutes on the relaxation times calculated from Stokesndash;Einsteinrsquo;s relation shows such situation can be caused from inertial motion of a solute molecule.
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