The effects of the correlation between vibration and rotation of partially oriented molecules on the N.M.R. parameters

Abstract

N.M.R. spectroscopy of partially oriented molecules provides a convenient technique for obtaining detailed information about molecular properties. However, the resulting data is sometimes internally inconsistent and markedly dependent on the conditions of the experiment, throwing some doubt on the general precision of the method. The probable reason for this is the correlation between the molecular vibrational and reorientational motion which is neglected in the conventional analysis. In this paper a theory for the effects of this correlation on the spectral parameters is elaborated. The resulting relation between molecular properties and spectral data is used to analyse the direct coupling constants of benzene measured in different liquid crystal solvents. The method solves the difficulties encountered in the conventional analysis: the molecular structure obtained proves to be internally consistent and solvent-independent. In addition to the structure the method yields also new information about the orienting forces.

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Notes on contributors

J. Lounila

On leave from the Department of Physics, University of Oulu, SF-90570 Oulu 57, Finland.