Nuclear Quadrupole Resonance and Its

Nuclear quadrupole resonance and its applications in inorganic chemistry. M. Kubo and D. Nakamura, Adv. Inorg. Chem. Radiochem., 1966, 8, 257-282 (78). 

Nuclear Quadrupole Resonance and Its Application in Inorganic Chemistry Masaji Kuho and Daiyu Nakamura... 

M. Kubo and D. Nakamura, Nuclear Quadrupole Resonance and Its Application in Inorganic Chemistry, in Advances in Inorganic Chemistry and Radiochemistry (H. J. Emeleus and A. G. Sharpe, eds.), Vol. 8, p. 257, Academic Press, New York (1966). 

A parameter, 17, used for describing nonsymmetric fields in nuclear quadrupole resonance spectroscopy. It is defined as 17 = ( xx field gradient q (which is the second derivative of the time-averaged electric potential) along the x-, y- and z-axes. By convention, refers to the largest field gradient, q-yy to the next largest, and q to the smallest when all three values are different. 

It was therefore felt to be timely to compile a monograph discussing the data obtained by a variety of spectroscopic techniques. The current volume thus attempts to fulfil that task by considering the techniques of infrared, nuclear quadrupole resonance and solid state NMR spectroscopy, together with neutron scattering studies. 

Various theoretical methods (self-consistent field molecular orbital (SCF-MO) modified neglect of diatomic overlap (MNDO), complete neglect of differential overlap (CNDO/2), intermediate neglect of differential overlap/screened approximation (INDO/S), and STO-3G ab initio) have been used to calculate the electron distribution, structural parameters, dipole moments, ionization potentials, and data relating to ultraviolet (UV), nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), photoelectron (PE), and microwave spectra of 1,3,4-oxadiazole and its derivatives <1984CHEC(6)427, 1996CHEC-II(4)268>. 

There are two basic ways to look for explosive material. They differ in their point of focus. Some sensors seek the mass of explosive material within a device. These are particularly useful when the device is well sealed and its surface is well cleaned of stray explosive molecules, or when the explosive being used is nonaromatic, that is, it does not readily release molecules from its bulk. We will refer to these as bulk sensors. They include X-ray techniques, both transmission and backscatter neutron activation in several techniques y -ray excitation, in either transmission or backscatter modes and nuclear resonance techniques, either nuclear magnetic resonance (NMR) or nuclear quadrupole resonance (NQR). Bruschini [1] has described these thoroughly. They are also described by the staff of the Jet Propulsion Laboratory [2], The following forms a very brief synopsis. 

These results have led us rather far from the apparently straightforward situation indicated by the first set of nuclear quadrupole resonance results, and serve to illustrate how complicated the whole question can become. Whatever the reasons for it however it is clear that the tetrahedral arrangement found in tetracoordinated Carbon compound is much less rigid in the heavier elements of the group. 

Yokagawa Electric Works has developed a thermometer based on the nuclear quadrupole resonance of potassium chlorate, usable over the range from —184 to 125°C. This thermometer makes use of the fundamental properties of the absorption frequency of the 35C1 nucleus, and its calibration is itself a constant of nature. 

An unambiguous success of the n-a overlap model of the anomeric effect is its ability to rationalise 35C1 nuclear quadrupole resonance frequencies in axial and equatorial glycopyranosyl chlorides (David, 1979). The axial chlorides invariably resonate at lower frequency, in accord with the more ionic nature of the C—Cl bond and hence the more spherically symmetrical distribution of electrons around the chlorine nucleus. 

The third problem also concerns the choice of whether to leave out certain material. In a book of this size it is not possible to cover all branches of spectroscopy. Such decisions are difficult ones but I have chosen not to include spin resonance spectroscopy (NMR and ESR), nuclear quadrupole resonance spectroscopy (NQR), and Mossbauer spectroscopy. The exclusion of these areas, which have been well covered in other texts, has been caused, I suppose, by the inclusion, in Chapter 8, of photoelectron spectroscopy (ultraviolet and X-ray), Auger electron spectroscopy, and extended X-ray absorption fine structure, including applications to studies of solid surfaces, and, in Chapter 9, the theory and some examples of lasers and some of their uses in spectroscopy. Most of the material in these two chapters will not be found in comparable texts but is of very great importance in spectroscopy today. 

Hegita H., Okuda T., Kashima M. Nuclear quadrupole resonance of antimony tribromide and its molecular complexes // J. Chem. Phys. - 1966. - Vol. 45. -P. 1076-1077. 

Nuclear quadrupole resonance spectroscopy (NQR) is a very direct and experimentally quite simple method for studying the interaction between the electric quadrupole moment of a nucleus and the electric field gradient at its site. Since the discovery of the method by Dehmelt and Kruger 3>6) in 1950, a large amount of experimental material has been collected, most of which has been interpreted within the frame of semiempirical theories. 

There are several papers and books 3-5> devoted to nuclear quadrupole resonance spectroscopy however, we think it better to begin with a brief survey of some of the theoretical aspects of pure quadrupole resonance for a spin I = 1, as well as of the experimental apparatus, before dealing with the detailed sxudy of nitrogen resonances. 

The theory of the magnetic hyperfine interactions in NCI is essentially the same as that already described for the PF radical in the previous section, except that the nuclear spins / are 1 for 14N and 3/2 for 35C1. The form of the effective Hamiltonian for the quadrupole interaction and its matrix elements for two different quadrupolar nuclei was described in some detail in chapter 8 when we discussed the electric resonance spectra of CsF and LiBr. We now use the same case (b) hyperfine-coupled basis set as was used for PF. The quadrupole Hamiltonian for the two nuclei can be written as the sum of two independent terms as follows ... 

NMR spectra of nuclei such as 57Fe (spin V2) in magnetic materials can be measured without external magnetic field. Also in the case of nuclear quadrupole resonance (NQR) no static magnetic field is necessary. For this reason NQR is sometimes called "zero field NMR". It is used to detect atoms whose nuclei have a nuclear quadrupole moment, such as 14N and 35C1. 

With the help of 35C1 Nuclear Quadrupole Resonance (NQR) spectroscopy and AMI, MNDO h PM3 calculation data of tautomers of 2-trichloromethyl-5(6)-nitrobenzimidazole it is established that 5-nitro tautomer is more preferable than its 6-isomer (Scheme 3.76) [1407],... 

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. 

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