Electron paramagnetic resonance nuclear quadrupole

Electron paramagnetic resonance (EPR) Quadrupole tensor, nuclear Zeeman splitting, g values, coupling constants, relaxation times Usually for odd electron metal sites probes ground-state wave function at high resolution... 

DPPH = 2,2-diphenyl-1-picrylhydrazyl ENDOR= electron-nuclear double resonance EPR = electron paramagnetic resonance ESE = electron spin echoes ESEEM = electron spin echo envelope modulation EFT = fast fourier transformations FWHM = fidl width at half maximum HYSCORE = hyperfine sublevel correlation nqi = nuclear quadrupole interaction TauD = taurme/aKG dioxygenase TWTA = traveling wave tube amphfier ZFS = zero field sphtting. 

This review article is concerned with the structure, bonding, and dynamic processes of water molecules in crystalline solid hydrates. The most important experimental techniques in this field are structural analyses by both X-ray and neutron diffraction as well as infrared and Raman spectroscopic measurements. However, nuclear magnetic resonance, inelastic and quasi elastic neutron scattering, and certain less frequently used techniques, such as nuclear quadrupole resonance, electron paramagnetic resonance, and conductivity and permittivity measurements, are also relevant to solid hydrate research. 

Deuterium quadrupole coupling constants can also be obtained from electron nuclear double resonance (ENDOR).19 30 An observation of the hyperfine structure caused by quadrupole coupling in the electron paramagnetic resonance (EPR) spectrum, as for many lanthanide complexes, has not been reported for deuterium. The determination of nuclear quadrupole coupling constants from Mossbauer spectroscopy is not applicable to the deuterium nucleus. 

Fig. 39. EPR (electron paramagnetic resonance) spectra of above N C6o centre N Qi (COOEt)2 together with below a simulation. The triplet splitting (above) is due to the isotropic hyperfine interaction of the electron systems with the nuclear spin Z = 1 of (natural abundance 99.6 %). Since the electronic spin is S = 3/2 (three unpaired electrons), each of the lines is three-fold degenerate. The occurrence of this degeneracy implies that the fine structure, quadrupole interaction and anisotropic hyperfine interaction are zero (complete spherical symmetry of nitrogen). In the adduct N C6i(COOEt)2 the icosahedral cage symmetry and therefore the degeneracy of nitrogen p orbitals is broken giving rise to new lines (centre). The simulation (below) is performed with the hyperfine interaction and g factor of N Cgo but in addition a fine structure interaction (D =2 G and E = 0.13 G) is included. The effect of the deviation from spherical symmetry on the quadrupole or anisotropic hyperfine interaction is too small to be detected...

Besides NQR spectroscopy and the study of nuclear quadrupole interaction effects in broad-line NMR spectroscopy, paramagnetic electron resonance 6°1, Mossbauer spectroscopy, and the study of perturbed angular correlation of y-rays, are suitable methods for studying nuclear quadrupole interactions in solids. Indirect methods are also available for acquiring information about the nuclear quadrupole couplinjg constant from the liquid state (particularly NMR spectroscopy in liquids and in liquid crystals in some cases gives information about this constant). By microwave spectroscopy, the nuclear quadrupole interaction may be studied in the gaseous phase (see the paper by Zeil). We shall deal here only with the aspect of NQR spectroscopy in solids since this method has the broadest applicability to chemical problems in comparison with the other methods mentioned. 

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