DIPOLE-DIPOLE INTERACTIONS OF A SPIN-1/2 NUCLEUS WITH A QUARDRUPOLE-COUPLED NUCLEUS.
ILLINOIS UNIV URBANA DEPT OF CHEMISTRY AND CHEMICAL ENGINEERING
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In recent nmr experiments, the dipolar broadening of the proton resonance in solid HMnCO5 and HCoCO4 has been used to estimate the metal-hydrogen bond distance. The M-H bond distances thus obtained are exceptionally short, 1.28 A for Mn-H and 1.42 A for Co-H. However, the analyses were based on the Van Vleck second moment expression which assumes that the nuclei are quantized in the direction z of the static magnetic field Ho and which therefore neglects any quadrupole coupling effects at the metal nucleus. This communication describes a theoretical analysis and numerical calculations for a two-spin 12, 72 system, having axial symmetry along the internuclear vector r and quadrupole coupling at the spin-72 nucleus. It is found that the second moment M2 of the spin-12 nucleus may be as much as 1.84 times its value in the absence of the quadrupole coupling. Therefore, the M-H bond distances reported previously may be as much as 12 too small. Author
- Atomic and Molecular Physics and Spectroscopy
- Nuclear Physics and Elementary Particle Physics