Quadrupolar intensities

Fig. 9. Polarised absorption spectra of three different polarisations in the spectrum of Cs2U02Cl4 at 4.2 K, showing the quadrupolar intensity of the feature at 20,405 cm-1 from Ref. [31]...

The centric scan, one-dimensional, DHK SPRITE measurement was used to study the ingress of lithium. This measurement technique was selected due to the low absolute sensitivity of 7Li (27% of [36]), the small amounts that are present and the short signal lifetimes (bulk Tx of 10 ms and T2 of 120 ps). In addition to the robust, quantitative nature of this technique, lithium is a quadrupolar nucleus and interpretation of the image intensity is more complex than spin % nuclei. Once again Eq. (3.4.2) is quantitatively correct for even quadrupolar nuclei due to the fact the longitudinal steady state does not influence the image intensity. 

Two factors contribute to r K. One is the ratio of the magnetogryric ratios of the two different spins, and the other depends on relaxation mechanisms. Provided that the relaxation mechanism is purely dipole-dipole, other relaxation mechanisms affect spin I, then 4> may approach zero. Assuming that the dipolar mechanism is operational (no quadrupolar nuclei with I > 1/2 are present), r has the value ys/ 2y and is regarded as rimax. In the homonuclear case we have r max = 1/ 2. Usually one chooses nuclei where ys > y/ to ensure that the NOE is significant. For observation of 13C for instance, if the protons in the molecule are double irradiated, the ratio is 1.99 and 1 + r max equals approximately 3. To repeat a statement made above, proton broad-band irradiation enhances the intensity of the 13C nucleus, which otherwise has very low receptivity. 

Figure 2. Near-field intensity portraits of a WG-Uke mode in (a) a square microdisk resonator and (b) a bow-tie mode in a quadrupolar (stadium) resonator and (c) a monopole mode in a hexagonal photonic crystal defect cavity (Boriskina, 2005).

Samoson, A. and Lippmaa, E. (1983) Excitation phenomena and line intensities in high-resolution NMR powder spectra of half-integer quadrupolar nuclei. Phys. Rev. E, 28, 6567-6570. 

The H2-He spectra may also be decomposed into translational and rotational line profiles, Fig. 3.13, similarly as this was sketched above for hydrogen, Fig. 3.11. In contrast to the decomposition for H2-H2 pairs, for the translational line of H2-He we must assume different profiles for the translational profile on the one hand, and the rotational profiles on the other [123]. The translational line of H2-He arises mainly from overlap induction which is of a much shorter range than the quadrupolar induction which shapes the rotational lines. As a consequence, at any given temperature, the translational line is much broader than the rotational lines. In the case of H2-He, it is also much more intense. 

If one assumes quadrupolar induction as the principal induction process, these total intensities of the H2-X systems should scale as the polarizability... 

---