Nuclear quadrupole resonance coupling constants

T. P. Das and E. L. Hahn, Nuclear Quadrupole Resonance Spectroscopy, Academic Press, New York, 1958, 223 pp E. A. C. Lucken, Nuclear Quadrupole Coupling Constants, Academic Press, London, 1969, 360 pp. 

Nuclear quadrupole resonance, 8 257-282 effect of cations on, 8 273-275 metal-ligand bond study by, 8 264-273 quadrupole coupling constant and, 8 250-260... 

Another important nuclear characteristic is the nuclear quadrupole moment which, possessed by nuclei for which 7 1, has given rise to the important field of nuclear quadrupole resonance spectroscopy. A major importance of the quadrupole moment with respect to NMR absorption resides in the effects of quadrupole coupling constants on nuclear relaxation times and, therefore, on the line widths and saturation characteristics of NMR absorption (9). In addition, in favorable situations, quadrupole coupling constants can be derived from the characteristics of nuclear resonance of quadrupolar nuclei 127). Some examples of these effects will be described in Sections III, IV and VI of this chapter. 

Nuclear Quadrupole Resonance (NQR) [50-54], Nuclear (electric) quadrupole resonance (NQR) was invented in 1950 [55] and is applicable to nuclei with nonzero nuclear electric quadrupoles eQ, which are 3x3 tensors, whose significant components are the quadrupole coupling constant QCC ... 

By convention nuclear quadrupole coupling constants are quoted as the quantity e2Qqzjh and expressed in frequency units, usually MHz. It must be noted that nuclear quadrupole resonance frequencies cannot be used to determine the sign of the coupling constant and that only its magnitude can be determined. 

No N nuclear quadrupole resonance (NQR) studies have been reported for transition metal nitrosyl complexes. This technique is expected to show interesting differences between linear and bent nitro-syls since the values of the quadrupole coupling constant and the asymmetry parameter depend on the relative populations of the nitrogen s,p, py, andpz orbitals. NQR spectroscopy has been used to study organic and inorganic nitroso compounds, and it is found that both... 

The nuclear quadrupole interaction often produces measurable effects in electronic, rotational, atomic and molecular beam resonance, nuclear magnetic resonance, and MOssbauer spectra. In many cases it can be directly studied by nuclear quadrupole resonance (NQR). The magnitude of interaction is expressed by the nuclear quadrupole coupling constant, e2qQ/hy which is the product of Eq. (1) and (3) expressed as a frequency. 

Still another source of information is nuclear quadrupole resonance spectroscopy. Waddington and Smith (96a) have used the C1 resonance to obtain evidence of genuine symmetry in the ions ClHCl- and C1DC1 in a salt known (97) to have a Type A structure with respect to the HCla ion. Hadzi and his co-workers (97a) have used deuteron resonance to study the structure of KDZg, where HX = trifluoroacetic acid (see Sect. VII D and XX G). The coupling constant and asymmetry para-... 

The quadrupole coupling constants obtained from the and quadru-pole interactions are exactly analogous to those measured by the nuclear quadrupole resonance method, and where figures are available for both, the... 

In this section, we attempt to review the solid-state Co NMR data published up to the end of 1998. The data on chemical shift tensors and quadrupole coupling constants are summarized in Tables 1-4. Data obtained by nuclear quadrupole resonance (NQR) are included wherever appropriate. Readers interested in the spin-spin coupling between spin-1 /2 and Co nuclei are referred to an article by Wasylishen and colleagues and the references cited therein. The NMR conventions employed in this review are defined in the next section. This is followed by a discussion of the techniques that have been applied to solid-state Co NMR studies with emphasis on what has been applied to Co systems. A detailed discussion on the techniques and Hamiltonians for quadrupolar nuclei is referred to the comprehensive review by Freude and Haase. 

In so-called pure nuclear quadrupole resonance (NQR) spectroscopy, the magnetic dipole transitions between the levels of (18.51) satisfy the selection rule Am = 1. For spin i there are two transitions, = 3eQVzzl20h and P2 = 2vi when T) = 0. For spin I, = eQVzJ 4h and = 2pi, ps = 3pi when t = 0. In these cases both the coupling constant, eQVzz, and asymmetry parameter may be determined from frequency measurements alone. 

Semin, G. K. Babushkina, T. A. Yakobson, G. G. Nuclear Quadrupole Resonance in Chemistry, Khimiya Leningrad 1972 English translation, Halsted-Wiley Chichester, 1975 Lucken, E. A. C. Nuclear Quadrupole Coupling Constants, Academic Press New York, 1969. 

Quadrupole coupling constants for molecules are usually determined from the hyperfine structure of pure rotational spectra or from electric-beam and magnetic-beam resonance spectroscopies. Nuclear magnetic resonance, electron spin resonance and Mossbauer spectroscopies are also routes to the property. There is a large amount of experimental data for and halogen-substituted molecules. Less data is available for deuterium because the nuclear quadrupole is small. 

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