The longitudinal nuclear magnetic relaxation time, T 1 , of powdered samples was analyzed following the theory proposed by Browstein and Tarr to explain the T 1 reduction of water confined in biological cells and the proposed by Rabbani and Edmonds where the molecular diffusion in liquids is substituted by spin diffusion to interpret the T 1 behavior in solid particles. We have shown that the multiexponential character of magnetization decay in solid particles with a narrow band size distribution allows to evaluate the spin diffusion coefficient of this material. On the other hand if the diffusion coefficient of a material is given and the average size of a sample of this material is known the relaxation decay curve can be used to determine the surface relaxivity as well as the relative size of particles present in the other samples of same material. However, this analysis is unable to provide the absolut measurement of the grain sizes. Furthermore, it is shown that the grain geometry does not influence the relaxation decay curve.

The temperature dependence of the average lattice mode frequency of a molecule undergoing librational motion in a quasi-harmonic potential has been calculated with the purpose of finding an explicit relationship between the observed shift of Raman spectral lines with temperature and the anharmonic term in the rotational potential. Calculations were carried out both for uncoupled and coupled oscillators. The equations obtained with this model provide good fittings for solid Cl2 and benzene data. This result can be applied to the analysis of the temperature dependence of NQR frequencies in molecular crystals.

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