High-held magnetization

This is what happens when a proton couples to different groups of protons with different coupling constants. Many different coupling patterns are possible, many can be interpreted, but others cannot. However, machines with high held magnets make the interpretation easier. As a demonstration, let us turn back to the bee alarm pheromone that we met in Chapter 3. An old 90 MHz NMR spec-... 

Electrochemical nuclear magnetic resonance (NMR) is a relatively new technique that has recently been reviewed (Babu et al., 2003). NMR has low sensitivity, and a typical high-held NMR instrument needs 10 to 10 NMR active atoms (e.g., spins), to collect good data in a reasonable time period. Since 1 cm of a single-crystal metal contains about 10 atoms, at least 1 m of surface area is needed to meet the NMR sensitivity requirement. This can be met by working with carbon-supported platinum... 

Phosphorus-31 MRS is continuing to advance and see wider application. The capability to perform P MRS on both clinical and high-held animal scanners is steadily becoming more widespread. Advances such as high magnetic fields and improved RF hardware, data-acquisition approaches, spectrum analysis automation, and pulse sequences promise a technique of increased speed and spectral and spatial resolution, with a widening range of potential applicahons. 

The further layout of the experiment consists of a hrst sextupole SI as a spin selector, a microwave cavity, and a second sextupole S2 as a spin analyzer (cf. Fig. 8). Since the magnetic held in SI is higher on the outside, the low-held seekers (1,1) and (1,0) will be focused, while the high-held seekers will move towards the magnet poles and annihilate there. We further assume that the states with Mp = 0 that have no permanent magnetic moment will loose their orientation in the held-free region before SI, so that after SI only atoms in the state (1,1) will remain. 

This initial growth was a little too early for n.m.r. to establish itself in the same way as it would have done had the development been delayed for 10 years. The unfortunate consequence of this is that the data available on many of the simple derivatives are rather scattered, and very few systematic studies have been undertaken most of the work tends to be centred around an isolated number of related compounds. The same situation is not the case with the carboranes, in which the study of the B resonance spectra have been used to ascertain the symmetry of the insertion of the carbon atoms this is amply illustrated by reference to the Annual Reports of the Chemical Society for 1965 and 1966. However in most studies of carboranes, the B spectra are very complex at the lower frequencies and the powerful applications of the high-held superconducting magnets have been amply demonstrated in this work. Unfortunately, these facilities are not available to many workers, and so assignments of the resonance signals of complex carborane derivatives are by no means as complete as would be desired. 

---