Nuclear spin coupling

Electron spin resonance (ESR), or electron paramagnetic resonance (EPR) as it is sometimes known, shares many similarities with its cousin, NMR. The origin of the phenomenon is the spin of the electron (rather than the nuclear spin) coupling with the nuclear spins of the atoms in the polymer, but much of the physics of their interactions are similar. The usual spin Hamiltonian, which is used to determine the energies of the interactions, can be written as... 

Pople, J. A., Santry, D. P. . Molecular Orbital Theory of Nuclear Spin Coupling Constants. Mol. Phys. 8, 1 (1964). 

Pople,J. A., Bothner-By, A.A. Nuclear Spin Coupling between Geminal Hydrogen Atoms. J. Chem. Phys. 42, 1339 (1965). 

Evans, D. F. Solvent Shifts of Nuclear Spin Coupling Constants due to Hydrogen Bonding. J. Chem. Soc. 1963, 5575,... 

From an analysis of the LDBSs developed in the previous sections one can also gain insight on which parts of the electronic structure of the molecules are relevant or irrelevant for the transmission of the indirect nuclear spin coupling through the molecule. 

In this work, results of high level ab initio SOPPA calculations of vicinal fluorine-fluorine indirect nuclear spin couplings are presented for 1,2-difluoroethene, -propene, -ethane and -propane. The four contributions (OD, OP, SD, FC) and the total value of the coupling constant are analyzed. 

N. M. R. Nuclear spin — Nuclear spin coupling constants... 

A calculation of the contact contributions to nuclear spin coupling in the H-D molecule has been carried out (114) using the James-Coolidge wave function (55). This calculation gave... 

H2 (the simplest possible compound) also exhibits a well-known S0 0 associated with the ortho para distribution of nuclear spins in the crystalline lattice, arising from the fact that each H nucleus (proton) has intrinsic nuclear spin I = According to the Pauli restriction for identical fermions, the two nuclear spins of diatomic H2 can couple into singlet ( ortho ) or triplet ( para ) spin states in statistical 3 1 proportions. Because the nuclear spin couplings are essentially independent of the electronic interactions that lead to formation of molecules and crystals, the ortho and para nuclear spin states distribute randomly throughout the H2 lattice, leading to conspicuous S0 7 0. 

Rehder, D., Dorn, W.L. and Schmidt, J. (1976b) Nuclear-spin coupling constants and bonding in phosphine-substituted carbonyl-vanadium compounds. Trans. Metal Chem., 1, 233-238. 

Following Hilbom, Gallagher and Ramsey [62] we use the same nuclear spin coupled basis set as we used for the weak field CsF analysis, i.e. rj, A J, /1, / ), /2, F, MF). All of the required matrix elements were calculated earlier except for those of the quadrupole interaction involving nucleus 2 (Li), which are,... 

The matrix elements of the third term in equation (8.351) are somewhat more complicated. Dealing first with the nuclear spin coupling, we have, as usual,... 

We deal first with the 14N quadrupole interaction, using the first term in (10.88), and making use of the results described in chapter 8 for the weak field coupled basis in CsF. The nuclear spin coupling scheme is... 

A. D. Buckingham and I. Love, Theory of the anisotropy of nuclear spin coupling.. Magn. Reson., 1970,2,338-351. 

Bally and Rablen ° followed up their important study of the appropriate basis sets and density functional needed to compute NMR chemical shifts with an examination of procedures for computing proton-proton coupling constants." They performed a comparison of 165 experimental with computed proton-proton coupling constants from 66 small, rigid molecules. They tested a variety of basis sets and functionals, along with questioning whether all four components that lead to nuclear-nuclear spin coupling constants are required, or if just the Fermi contact term would suffice. 

Consider a product nucleus i (or a group of equivalent nuclei) which was part of the radical R in the pair R R, and which is coupled to nucleus / in the product with the nuclear spin coupling constant The polarizations of the transitions of the NMR multiplet of this nucleus i may then be described as the superposition of a net effect and a multiplet effect, i.e. of two quantities r andr ,3 )... 

Legon, A. C. and Suckley, A. R, Br nuclear quadrupole and H,Br nuclear-spin-nuclear-spin coupling in the rotational spectrum of H20 HBr, Chem. Phys. Lett. 150, 153-158 (1988). 

---