GENERALIZED VALENCE BOND THEORY OF NUCLEAR SPIN-SPIN INTERACTION IN $^{1}\Sigma$ MOLECULES; APPLICATION TO $C^{13}$ AND $F^{19}$ SPIN COUPLINGS

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1961

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Ohio State University

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Expressions for nuclear spin-spin coupling constants (J) in $^{1}\Sigma$ molecules are obtained with a generalized valence bond (v.b.) function and second-order perturbation theory. Both electron-spin and electron-orbital contributions are included in the formulation. For evaluating the contact and dipolar spin terms, a modification of the usual Rumer-Pauling rules is developed. “Long-range” approximations for J in the v.b. scheme are introduced and the required integrals are calculated with suitable atomic orbitals. It is found that earlier $estimates^{1,2}$ of some of these integrals are considerably in error. Applications to coupling constants involving $C^{13}$ and $F^{19}$ nuclei are given for typical systems. The v.b. expressions for J derived here are more general in that all terms besides the “contact” term are considered. Further, the present theory is applicable to directly bonded as well as non-bonded nuclei.

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$^{1}$H. M. McConnell, J Chem. Phys., 24, 460 (1956). $^{2}$G. A. Williams and H. S. Gutowsky, J. Chem. Phys., 30, 717 (1959).
Author Institution: Department of Chemistry, Columbia University

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