Selected Applications of Nuclear Spin Relaxation

Selected applications of nuclear spin relaxation in liquids... 

We have demonstrated that the principle of multiple selective excitation with subsequent data processing appropriate to disentangle the superimposed responses may successfully be incorporated into selective ID and 2D pulse sequences. This allows to improve the overall efficiency especially of experiments with an inherent low sensitivity. In most of the presented examples a series of single selective pulses has been applied, giving rise to unwanted relaxation losses and setting an upper limit to the number of perturbed nuclear spins. With the application of single multiple selec-... 

In section II.A.2. we discussed how the rf pulse acts on the nuclear spins. We now discuss this topic further and apply the results to several examples having to do with selective excitation. There are many reasons for wanting to perform selective excitation in NMR. Some of them are to simplify complex spectra, to do selective population transfer in order to get the sign of spin-spin coupling, and to study cross relaxation. An important application of what we might call selective de-excitation is a notch in the irradiation pattern to suppress an unwanted resonance such as the solvent peak in a complex proton spectrum. Morris and Freeman (1978) have reviewed many aspects of such experiments. 

The well-defined cages and pores of zeolites allow the application of these materials as molecular sieves and form-selective catalysts in heterogeneous catalysis. Xe NMR spectroscopy of xenon atoms adsorbed on zeolites is a suitable method for the characterization of the zeolitic pore architecture. The isotope Xe has a nuclear spin of 1=112, a natural abundance of 26.4% and, adsorbed on zeolites, a Ti relaxation time in the range between 10 ms and a few seconds. 

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