Quadrupolar frequency

When the Zeeman interaction is much larger than the quadrupolar frequency (coo coq), the averaged quadmpolar Hamiltonian over a Larmor period,... 

Since both excitation and conversion are dependent on r, MQ spectra are normally not directly quantitative, so great care has to be taken to interpret the spectra. The situation will generally improve as the applied rf field increases. Since the 2D data set contains the anisotropic information, lineshapes can be analysed and the quadrupolar parameters deduced. The lineshape will show distortion as there will be crystallites whose orientation is such that their quadrupolar frequency is zero and will not contribute. Apart from the excitation and the conversion, the actual coherence pathway... 

Because it simpUfies equations, the use of ooq (or Vq, in Hz) is often preferred over Cq. Moreover, the quadrupolar frequency describes well the actual... 

In angular units of frequency, the NQCC is given by x = eqe( lThe quadrupolar frequency is defined in angular units as (see Ref. 2)... 

Therefore, we choose to define the quadrupolar Hamiltonian in terms of the quadrupolar frequency as... 

In general, the best MQMAS sequence for the highest resolution in any quadrupolar spin system is obtained with the use of an MQNQ experiment." Here, for instance, in a spin- system, instead of correlating either the 5Q or 3Q with SQC, the second-order quadrupolar frequencies resulting from a 5QC evolution period are refocused with 3QC evolution and only then transferred and detected via SQC. The pulse sequence for this is shown in Fig. 8a where both SQC and 3QC are subjected to a fj evolution (split-fj) to refocus second-order quadrupolar broadening. This, though yielding a better resolution, is prone to sensitivity problems more than other MQMAS schemes. 

The chemical shift range for deuterium, as well as its dipolar and scalar interactions, are of the order of only a few (<5) kHz at 11.7 T. Thus, they can be ignored in view of the dominant quadrupolar coupling constant, which is e Qlh — 167 kHz for aliphatic C— H bonds [19, 21]. Here, e is the elementary charge and eq the largest field gradient. Q = 2.875 x 10 cm is the scalar quadrupole moment for the deuteron, and h is Planck s constant. Since the deuterium quadrupolar frequency is much smaller than the Zeeman frequency difference, the H NMR spectrum can be described by treating the quadrupolar interaction as a first-order perturbation of the Zeeman interaction [1, 19, 21, 60]. 

Temperature dependence of Cl signal was studied quadrupolar frequency varies by 0.75 kHz K (120-260 K)... 

Figure 3 Energy level splittings and transitions for half-integer quadrupolar nuclei, as illustrated for the example of a spin-3/2 nucleus, (Oy is the NMR transition frequency in the absence of the quadrupolar interaction, Wy is the quadrupolar frequency, and 0 is the angle between the magnetic field and the principal axis of the electric field gradient tensor.

Considering now Fig. 8 (b) and the spectra of bipolar droplets in the fast translational diffusion limit (or, equivalently, in small enough nematic droplets), the spectra for all 77 still consist of two well-defined lines now positioned, however, at an average quadrupolar frequency given by... 

The chlorobenzenes give another example of the influence of the substituent groups on the quadrupolar frequency of chlorine. By an examination of the experimental data the mean shifts of the frequency of a given chlorine atom of the molecule, caused by... 

The quadrupolar interaction is typically treated as a perturbation, to second order, of the dominant Zeeman interaction when describing the SSNMR spectra of quadrupolar nuclei. This approach has been enormously successful. For nuclei with particularly strong quadrupolar interactions, however, it is not surprising that this perturbation theoretical approach may break down under appropriate conditions (i.e., where the quadrupolar frequency (i/q) becomes comparable to the Larmor frequency (i/q))- During the reporting period, quadrupolar halogen SSNMR studies have provided valuable... 

A combined " Ga SSNMR and NQR study of the synthetic reagent known as Gal elucidated its precise composition [55]. Although no SSNMR spectra are reported, the gallium NMR data as well as the quadrupolar frequencies determined from NQR allowed for Gal to be identified as two equivalents of Ga metal with two equivalents of Gal2, where the latter is composed of Ga and Gal4 ions. The NMR and NQR data therefore surest the following formulation [Ga%[Ga] [Gal4]. ... 

Original article was written in German it is not clear if these are quadrupolar coupling constants (Cq) or quadrupolar frequencies (i Q). 

Satellite Transition Spectroscopy (SATRAS) [9,10] has been proven to be a useful technique to determine the NMR parameters of quadrupolar spin systems, in particular when the quadrupolar frequency Uq is so small that the structure of the central transition (CT) 1/2 —1/2 due to second-order effects is not resolved. In that case, reliable informa-... 

---