Quasielastic Scattering of Thermal Neutrons by CH3OH and CH3SH

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Abstract
We report measurements of the line broadening of thermal neutrons quasielastically scattered from room temperature methyl alcohol and methyl mercaptan in the liquid phase. The linewidths for CH3SH are found to be approximately twice those of CH3OH. This is interpreted to be additional evidence of the relative freedom of molecular motions and lack of hydrogen bonding in CH3SH. The linewidth data are discussed in terms of the simple diffusion model, and for methanol, in terms of a globular diffusion model. For methanol a diffusion constant of 3.25 × 10−5 cm2sec−1 and a diffusing globule mass of ∼3.5 molecules are in agreement with the data. An upper limit of D = 6.5 × 10−5cm2sec−1 is found for the diffusion constant of CH3SH.