In nuclear quadrupole coupling

K magnitude of the changes in nuclear quadrupole coupling constants in going from metal halide to noble gas-metal halide. 

Lucken, E. A. C. In Nuclear Quadrupole Coupling Constants , Academic Press, London 1969. 

As follows from the data in Table 7, the introduction of NO2 and CH3 at positions 2 and 5 of the imidazole ring, respectively, leads to an increase in nuclear quadrupole coupling constants on both nitrogens of the ring and a decrease in the value of this parameter on the nitrogen from the NO2 group. Results of a bond population analysis carried out according to the Townes-Dailey method for imidazole and its derivatives are displayed in Table 8. 

Pyykko P and Seth M 1997 Relativistic effects in nuclear quadrupole coupling. Theor. Chem. Acc. 96, 92-104. 

Schwerdtfeger, P., Pernpointner, M. and Nazarewicz, W. (2004) Calculation of Nuclear Quadrupole Coupling Constants, in Calculation ofNMR and EPR Parameters Theory and Applications, (eds M. Kaupp M. Biihl and V.G. Malkin), Wiley-VCH Verlag GmbH, Weinheim, pp. 279-291. 

Lantto, P. and Vaara, J. (2006) Calculations of nuclear quadrupole coupling in noble gas-noble metal fluorides Interplay of relativistic and electron correlation effects. Journal of Chemical Physics, 125, 174315-1-174315-7. 

The experimentally observed quadrupole splitting AEq for Fe in inorganic compounds, metals, and solids reaches from 0 to more than 6 mm s [30, 32]. The range of AEq for other Mossbauer isotopes may be completely different because of the different nuclear quadrupole moment Q of the respective Mossbauer nucleus, and also because the EFG values may be intrinsically different due to markedly different radial distributions of the atomic orbitals (vide infra). As Q is constant for a given isotope, variations in the quadrupole coupling constants eQV can only arise from... 

RBa2Cu40g (R = Sm, Y, Er) Nuclear-quadrupole coupling parameters at the rare-earth metal and copper sites from Cu ( Zn) and Ga( Zn) Mossbauer emission spectroscopy, EEG tensor in comparison with point charge model, shows that holes in lattices are localized primarily at chain-oxygen sites... 

Other key properties of these complexes relevant for comparison with experiment are the nuclear quadrupole coupling constants. Theoretical NQCC values, as calculated via electric field gradients, are discussed exhaustively in several recent theoretical investigations [26,28,30,33,34] and in experimental work [4-11]. BH HLYP/aug-cc-pVTZ calculated NQCCs [30,34], as evaluated for XY- -NH3 complexes, are listed in Table 10. 

Oxirane is an important Lewis base in the present context. The O atom carries two equivalent n-pairs of electrons, as it does in H20, but oxirane has the advantage over water in that it is possible to determine both angles 0 and 9 for its complexes with HC1 and ClF because the non-zero off-diagonal element Xab(Cl) of the Cl nuclear quadrupole coupling tensor is available. The corresponding Lewis base in which an S atom carries two equivalent n-pairs is thiirane. Each of the pair of complexes (CL S- -HC1 and (CL S- -ClF has Cs symmetry and here it is the off-diagonal element Xac(Cl) that is non-zero... 

In Sect. 2, it was indicated that changes AXap(X) and A/ / (Y) in halogen nuclear quadrupole coupling constants xap X) and Xafs(Y) of a dihalogen... 

We assume that, on formation of B- XY, a fraction 5j (i = intermolecular) of an electronic charge is transferred from the electron donor atom of Z of the Lewis base B to the npz orbital of X and that similarly a fraction 5p (p = polarisation) of an electronic charge is transferred from npz of X to n pz of Y, where z is the XY internuclear axis and n and n are the valence-shell principal quantum numbers of X and Y. Within the approximations of the Townes-Dailey model [187], the nuclear quadrupole coupling constants at X and Y in the hypothetical equilibrium state of B- -XY can be shown [178] to be given by ... 

The spectra discussed in Chapter 4 were analyzed by neglecting the effects of nuclear quadrupole coupling on the nuclear hyperfine structure. Presented here is the way such effects may be incorporated into the spectra using perturbation theory. 

Preliminary Cu-ENDOR results on Cu(salen) show that the nuclear quadrupole coupling constant of the copper ions lies in the range between those for square planar 04 and S202 coordinated copper complexes177. ... 

Relations Between Nuclear Quadrupole Coupling Constants in Different Expressions of 9 q (Sect. 5.2))... 

ENDOR experiments can be performed in liquid solution, in which only the isotropic hfc s (Ajso) are detected. They are proportional to the spin density at the respective nucleus. Erom the assigned isotropic hfc s a map of the spin density distribution over the molecule can be obtained. In frozen solutions and powders the anisotropic hf interactions can also be determined. Eurthermore, the method allows the detection of nuclear quadrupole couplings for nuclei with 1 1. For dominant g anisotropy as found in many metal complexes the external magnetic field can be set to several specific g values in the EPR, thereby selecting only those molecules that have their g tensor axis along the chosen field direction. In such orientation-selected spectra only those hf components are selected that correspond to this molecular orientation ( single crystal-like ENDOR ). 

Gordy W. (1950). Interpretation of nuclear quadrupole couplings in molecules. J. Chem. Phys., 19 792-793. 

Fig. 5. Sigma orbital populations of the halogen atoms in Group IV tetrahalides obtained from the halogen nuclear quadrupole coupling constants by use of Equation (1) with an = 2.0...

The unpaired electron in these two molecules is now in exactly the right orbital for the present purposes, since d —Px bonding is usually invoked in order to stabilise such antibonding or non-bonding orbitals. As we have seen both the nuclear quadrupole coupling constant and the anisotropic electron-nuclear hyperfine coupling constant are dominated... 

T. J. Bastow, Temperature dependence of the nuclear quadrupole coupling and relaxation time of Mg in Mg metal. /. Pkifs. Condens. Matter, 1991, 3,753-756. 

---