Application of the Rovibrational Theory

An application of the basic ideas briefly reviewed in Sections 12.2 and 12.3 to NMR shielding has been formulated by Jameson. The isotope effect on the shielding (cr) depends on vibrationally averaged bond lengths and angles according to Equation 12.16 

For large molecules it is no longer feasible to carry out the complete anharmonic vibrational analysis implied by Equation 12.16. One is forced to the approximate relation, Equation 12.17, which seems to work pretty well in spite of the criticisms discussed above. Numerous examples abound in the literature. The interested student is referred to the review of Hansen. 

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