Quadrupole asymmetry parameter

Nuclear electric quadrupole QCC (quadrupole coupling constant), (asymmetry parameter) Line-shape analysis, nutation NMR Coordination symmetry... 

Most valuable chemical information can be extracted from Mbssbauer parameters such as the isomer shift (5), the quadrupole splitting (AEq), the magnetic splitting (AEm), and the asymmetry parameter (n). 

Here, I, I, and I are angular momentum operators, Q is the quadrupole moment of the nucleus, the z component, and r the asymmetry parameter of the electric field gradient (efg) tensor. We wish to construct the Hamiltonian for a nucleus if the efg jumps at random between HS and LS states. For this purpose, a random function of time / (f) is introduced which can assume only the two possible values +1. For convenience of presentation we assume equal... 

Since the EFG component E and the asymmetry parameter rj = (Fee Vyy)/V,. in the PAS are invariants of the EFG, the two similar arrangements of the charge q shown in Fig. 4.7a, b must produce the same quadrupole splitting (because energies do not depend on the choice of the coordinate system). 

An instructive description of the first-order perturbation treatment of the quadrupole interaction in Ni has been given by Travis and Spijkerman [3]. These authors also show in graphical form the quadrupole-spectrum line positions and the quadrupole-spectrum as a function of the asymmetry parameter r/ they give eigenvector coefficients and show the orientation dependence of the quadrupole-spectrum line intensities for a single crystal of a Ni compound. The reader is also referred to the article by Dunlap [15] about electric quadrupole interaction, in general. 

Fig. 7.33 Effect of a positive quadrupole interaction on the ground and first excited states of Ru. The asymmetry parameter r) is assumed to be zero. The ratio of the quadrupole moments is taken to be Q3/tJQs/2 = 3. a = e qQsn and B = e qQ a (from [124])...

Table 7.4 Quadrupole coupling constant eQV z and asymmetry parameter r) for hafnium compounds...

Isomer shift versus a-iron at RT Quadrupole splitting Asymmetry parameter... 

Figure 8 a shows the motionally averaged quadrupole coupling constant, (Cq)/Cq, and asymmetry parameter, ( ), for a two-site jump between axially symmetric equivalent sites. At jump angles of 70° and 109° the principal components (V, Vyy, Vzz) have to be rearranged in order, which leads to the discontinuities in the curve shapes of Fig. 8a. 

The temperature dependent T data are shown in Fig. 9. 7j values decrease from 28 ms at 21°C with increasing temperature, and show a minimum of 6.4 ms at 80° C. These results indicate the presence of the motion with a Larmor frequency of 30 MHz at this temperature. This minimum was found to be attributed to the flipping motion of a phenyl ring from the result of our other experiments discussed in later section.13 The jump rates of the flipping motion were estimated with a two-site jump model that a C-2H bond jumps between two equivalent sites separated by 180°, and that the angle made by the C-2H bond and the rotational axis is 60°. The quadrupole coupling constant of 180 kHz and the asymmetry parameter approximated to zero were used in the calculation. The calculated values for fitting with the... 

To calculate the nuclear quadrupole moment from the measured quadrupole splitting, it is necessary to know the electric field gradient, q, at the Te nucleus as well as the asymmetry parameter, rj. These can be calculated in the Townes and Dailey approximation (4) by knowing the chemical bonding in Te. 

The apparently unanimous verdict in favour of halogen metal multiple-bond character given by nuclear quadrupole resonance methods is unfortunately somewhat shaken by the results of Grayheal and Green (5) who measured (Table 4) the Chlorine asymmetry parameters of the... 

Table 4. pure quadrupole resonance frequencies and asymmetry parameters of Group IV tetrachlorides (5)... 

Some typical CT-only spectra simulated for static samples considering solely the quadrupole interaction are shown in Figure lA, for sites with different values of the asymmetry parameter r/q. The widths of these lineshapes depend on the rjq value and are proportional to the parameter A, defined for a nucleus with 1=5/2 as ° ... 

Al Quadrupole Coupling Constant, C-rjcc. ond Asymmetry Parameter, tj, of Framework Al Atoms in Dehydrated Zeolites Y (faujasite), MOR (mordenite), and ZSM-5... 

Table I. Quadrupole Coupling Constants, Asymmetry Parameters, and Distances of Singularities of the Powder Patterns for Two Models of the...

Conventional single-crystal studies of aluminosilicates date back to the early 1950 s, and principal components of the quadrupole-coupling tensors together with asymmetry parameters have been determined for a number of minerals (see Table XI). Wide-line-NMR measurements of the dependence of the 27A1 and 23Na quadrupole-coupling constants in analcime and zeolites Na-X and Na-A on the water content were carried out by Gabuda et al. (137). 

Two parameters describe the quadrupole interaction there are the quadrupole splitting and the asymmetry parameter, rj, which is defined as,... 

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